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Long DR, Kinser A, Olalde-Welling A, Brewer L, Lim J, Matheny D, Long B, Roossien DH. 5-HT1A regulates axon outgrowth in a subpopulation of Drosophila serotonergic neurons. Dev Neurobiol 2023; 83:268-281. [PMID: 37714743 DOI: 10.1002/dneu.22928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 09/02/2023] [Accepted: 09/04/2023] [Indexed: 09/17/2023]
Abstract
Serotonergic neurons produce extensively branched axons that fill most of the central nervous system, where they modulate a wide variety of behaviors. Many behavioral disorders have been correlated with defective serotonergic axon morphologies. Proper behavioral output therefore depends on the precise outgrowth and targeting of serotonergic axons during development. To direct outgrowth, serotonergic neurons utilize serotonin as a signaling molecule prior to it assuming its neurotransmitter role. This process, termed serotonin autoregulation, regulates axon outgrowth, branching, and varicosity development of serotonergic neurons. However, the receptor that mediates serotonin autoregulation is unknown. Here we asked if serotonin receptor 5-HT1A plays a role in serotonergic axon outgrowth and branching. Using cultured Drosophila serotonergic neurons, we found that exogenous serotonin reduced axon length and branching only in those expressing 5-HT1A. Pharmacological activation of 5-HT1A led to reduced axon length and branching, whereas the disruption of 5-HT1A rescued outgrowth in the presence of exogenous serotonin. Altogether this suggests that 5-HT1A is a serotonin autoreceptor in a subpopulation of serotonergic neurons and initiates signaling pathways that regulate axon outgrowth and branching during Drosophila development.
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Affiliation(s)
- Delaney R Long
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Ava Kinser
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | | | - Luke Brewer
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Juri Lim
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Dayle Matheny
- Department of Biology, Ball State University, Muncie, Indiana, USA
| | - Breanna Long
- Department of Biology, Ball State University, Muncie, Indiana, USA
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2
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McKinney HM, Sherer LM, Williams JL, Certel SJ, Stowers RS. Characterization of Drosophila octopamine receptor neuronal expression using MiMIC-converted Gal4 lines. J Comp Neurol 2020; 528:2174-2194. [PMID: 32060912 DOI: 10.1002/cne.24883] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/31/2020] [Accepted: 02/09/2020] [Indexed: 01/08/2023]
Abstract
Octopamine, the invertebrate analog of norepinephrine, is known to modulate a large variety of behaviors in Drosophila including feeding initiation, locomotion, aggression, and courtship, among many others. Significantly less is known about the identity of the neurons that receive octopamine input and how they mediate octopamine-regulated behaviors. Here, we characterize adult neuronal expression of MiMIC-converted Trojan-Gal4 lines for each of the five Drosophila octopamine receptors. Broad neuronal expression was observed for all five octopamine receptors, yet distinct differences among them were also apparent. Use of immunostaining for the octopamine neurotransmitter synthesis enzyme Tdc2, along with a novel genome-edited conditional Tdc2-LexA driver, revealed all five octopamine receptors express in Tdc2/octopamine neurons to varying degrees. This suggests autoreception may be an important circuit mechanism by which octopamine modulates behavior.
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Affiliation(s)
- Hannah M McKinney
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana
| | - Lewis M Sherer
- Cellular, Molecular and Microbial Biology Graduate Program, The University of Montana, Missoula, Montana
| | - Jessica L Williams
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana.,Department of Plant Sciences, Montana State University, Bozeman, Montana
| | - Sarah J Certel
- Cellular, Molecular and Microbial Biology Graduate Program, The University of Montana, Missoula, Montana.,Division of Biological Sciences, Center for Structural and Functional Neuroscience, The University of Montana, Missoula, Montana
| | - R Steven Stowers
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana
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3
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Yurchenko OV, Savelieva AV, Kolotuchina NK, Voronezhskaya EE, Dyachuk VA. Peripheral sensory neurons govern development of the nervous system in bivalve larvae. EvoDevo 2019; 10:22. [PMID: 31528326 PMCID: PMC6743156 DOI: 10.1186/s13227-019-0133-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 08/21/2019] [Indexed: 12/15/2022] Open
Abstract
Recent findings regarding early lophotrochozoan development have altered the conventional model of neurogenesis and revealed that peripheral sensory elements play a key role in the initial organization of the larval nervous system. Here, we describe the main neurogenetic events in bivalve mollusks in comparison with other Lophotrochozoa, emphasizing a novel role for early neurons in establishing larval nervous systems and speculating about the morphogenetic function of the apical organ. We demonstrate that during bivalve development, peripheral sensory neurons utilizing various transmitters differentiate before the apical organ emerges. The first neurons and their neurites serve as a scaffold for the development of the nervous system. During veliger stage, cerebral, pleural, and visceral ganglia form along the lateral (visceral) nerve cords in anterior-to-posterior axis. The pedal ganglia and corresponding ventral (pedal) nerve cords develop much later, after larval settlement and metamorphosis. Pharmacological abolishment of the serotonin gradient within the larval body disrupts the navigation of "pioneer" axons resulting in malformation of the whole nervous system architecture. Comparative morphological data on neurogenetic events in bivalve mollusks shed new light on the origin of the nervous system, mechanisms of early axon navigation, and sequence of the tetraneurous nervous system formation. Furthermore, this information improves our understanding of the basic nervous system architecture in larval Bivalvia and Mollusca.
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Affiliation(s)
- Olga V. Yurchenko
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Anna V. Savelieva
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Natalia K. Kolotuchina
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
| | - Elena E. Voronezhskaya
- N.K. Koltsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, 119991 Russia
| | - Vyacheslav A. Dyachuk
- National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Department of Nanophotonics and Metamaterials, ITMO University, St. Petersburg, Russia
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4
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De Santis M, Huang XF, Deng C. Early antipsychotic treatment in juvenile rats elicits long-term alterations to the adult serotonin receptors. Neuropsychiatr Dis Treat 2018; 14:1569-1583. [PMID: 29950841 PMCID: PMC6011877 DOI: 10.2147/ndt.s158545] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Antipsychotic drug (APD) prescription/use in children has increased significantly worldwide, despite limited insight into potential long-term effects of treatment on adult brain functioning. While initial long-term studies have uncovered alterations to behaviors following early APD treatment, further investigations into potential changes to receptor density levels of related neurotransmitter (NT) systems are required. METHODS The current investigation utilized an animal model for early APD treatment with aripiprazole, olanzapine, and risperidone in male and female juvenile rats to investigate potential long-term changes to the adult serotonin (5-HT) NT system. Levels of 5-HT1A, 5-HT2A, and 5-HT2C receptors were measured in the prefrontal cortex (PFC), caudate putamen (CPu), nucleus accumbens (NAc), and hippocampus via Western Blot and receptor autoradiography. RESULTS In the male cohort, long-term changes to 5-HT2A and 5-HT2C receptors were found mostly across hippocampal and cortical brain regions following early aripiprazole and olanzapine treatment, while early risperidone treatment changed 5-HT1A receptor levels in the NAc and PFC. Lesser effects were uncovered in the female cohort with aripiprazole, olanzapine and risperidone to alter 5-HT1A and 5-HT2A receptors in NAc and hippocampal brain regions, respectively. CONCLUSION The results of this study suggest that early treatment of various APDs in juvenile rats may cause gender and brain regional specific changes in 5-HT2A and 5-HT2C receptors in the adult brain.
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Affiliation(s)
- Michael De Santis
- Antipsychotic Research Laboratory, Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- School of Medicine, University of Wollongong, Wollongong, NSW, Australia
| | - Xu-Feng Huang
- School of Medicine, University of Wollongong, Wollongong, NSW, Australia
| | - Chao Deng
- Antipsychotic Research Laboratory, Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- School of Medicine, University of Wollongong, Wollongong, NSW, Australia
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Nezlin LP, Voronezhskaya EE. Early peripheral sensory neurons in the development of trochozoan animals. Russ J Dev Biol 2017. [DOI: 10.1134/s1062360417020060] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Wirth A, Holst K, Ponimaskin E. How serotonin receptors regulate morphogenic signalling in neurons. Prog Neurobiol 2017; 151:35-56. [DOI: 10.1016/j.pneurobio.2016.03.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 03/09/2016] [Accepted: 03/19/2016] [Indexed: 11/25/2022]
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Migliarini S, Pacini G, Pelosi B, Lunardi G, Pasqualetti M. Lack of brain serotonin affects postnatal development and serotonergic neuronal circuitry formation. Mol Psychiatry 2013; 18:1106-18. [PMID: 23007167 DOI: 10.1038/mp.2012.128] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 07/19/2012] [Accepted: 07/23/2012] [Indexed: 12/11/2022]
Abstract
Despite increasing evidence suggests that serotonin (5-HT) can influence neurogenesis, neuronal migration and circuitry formation, the precise role of 5-HT on central nervous system (CNS) development is only beginning to be elucidated. Moreover, how changes in serotonin homeostasis during critical developmental periods may have etiological relevance to human mental disorders, remains an unsolved question. In this study we address the consequences of 5-HT synthesis abrogation on CNS development using a knock-in mouse line in which the tryptophan hydroxylase 2 (Tph2) gene is replaced by the eGFP reporter. We report that lack of brain 5-HT results in a dramatic reduction of body growth rate and in 60% lethality within the first 3 weeks after birth, with no gross anatomical changes in the brain. Thanks to the specific expression of the eGFP, we could highlight the serotonergic system independently of 5-HT immunoreactivity. We found that lack of central serotonin produces severe abnormalities in the serotonergic circuitry formation with a brain region- and time- specific effect. Indeed, we observed a striking reduction of serotonergic innervation to the suprachiasmatic and thalamic paraventricular nuclei, while a marked serotonergic hyperinnervation was found in the nucleus accumbens and hippocampus of Tph2∷eGFP mutants. Finally, we demonstrated that BDNF expression is significantly up-regulated in the hippocampus of mice lacking brain 5-HT, mirroring the timing of the appearance of hyperinnervation and thus unmasking a possible regulatory feedback mechanism tuning the serotonergic neuronal circuitry formation. On the whole, these findings reveal that alterations of serotonin levels during CNS development affect the proper wiring of the brain that may produce long-lasting changes leading to neurodevelopmental disorders.
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Affiliation(s)
- S Migliarini
- Department of Biology, Unit of Cellular and Developmental Biology, University of Pisa, Pisa, Italy
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8
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Balog G, Voronezhskaya EE, Hiripi L, Elekes K. Organization of the serotonergic innervation of the feeding (buccal) musculature during the maturation of the pond snail Lymnaea stagnalis: a morphological and biochemical study. J Comp Neurol 2012; 520:315-29. [PMID: 21674495 DOI: 10.1002/cne.22693] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The serotonergic innervation of the buccal musculature responsible for feeding (radula protraction) was investigated during the maturation of the pond snail, Lymnaea stagnalis L., applying light and electron microscopic immunohistochemistry and biochemical approaches. According to epifluorescence and laser confocal microscopy, the first 5-HT-like-immunoreactive (5-HTLIR) processes appeared on the surface of the musculature at the postmetamorphic E80% embryonic stage. Until hatching, the innervation continued to increase in density, showing axon arborizations with projections into the deeper muscle levels. An adult-like pattern of 5-HTLIR innervation appeared at P2-P3 juvenile stages. At the ultrastructural level, close (16-20 nm) but mostly unspecialized neuromuscular contacts were formed by both unlabeled and 5-HTLIR axon profiles from the E80% embryonic stage. Labeled processes were also found located relatively far from the muscle cells. An HPLC assay showed a gradual increase of the 5-HT level in the buccal mass during development. The buccal mass was characterized by a single-component high-affinity 5-HT uptake system, and 5-HT release could be evoked by 100 mM K(+) and blocked in Ca(2+) -free medium. It is suggested that 5-HT plays a wide modulatory role in the peripheral feeding system and is also involved in the functional maturation of the muscle system.
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Affiliation(s)
- Gábor Balog
- Department of Experimental Zoology, Balaton Limnological Research Institute, Hungarian Academy of Sciences, H-8237 Tihany, Hungary
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9
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Neckameyer WS, Bhatt P. Neurotrophic actions of dopamine on the development of a serotonergic feeding circuit in Drosophila melanogaster. BMC Neurosci 2012; 13:26. [PMID: 22413901 PMCID: PMC3364880 DOI: 10.1186/1471-2202-13-26] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 03/13/2012] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND In the fruit fly, Drosophila melanogaster, serotonin functions both as a neurotransmitter to regulate larval feeding, and in the development of the stomatogastric feeding circuit. There is an inverse relationship between neuronal serotonin levels during late embryogenesis and the complexity of the serotonergic fibers projecting from the larval brain to the foregut, which correlate with perturbations in feeding, the functional output of the circuit. Dopamine does not modulate larval feeding, and dopaminergic fibers do not innervate the larval foregut. Since dopamine can function in central nervous system development, separate from its role as a neurotransmitter, the role of neuronal dopamine was assessed on the development, and mature function, of the 5-HT larval feeding circuit. RESULTS Both decreased and increased neuronal dopamine levels in late embryogenesis during development of this circuit result in depressed levels of larval feeding. Perturbations in neuronal dopamine during this developmental period also result in greater branch complexity of the serotonergic fibers innervating the gut, as well as increased size and number of the serotonin-containing vesicles along the neurite length. This neurotrophic action for dopamine is modulated by the D2 dopamine receptor expressed during late embryogenesis in central 5-HT neurons. Animals carrying transgenic RNAi constructs to knock down both dopamine and serotonin synthesis in the central nervous system display normal feeding and fiber architecture. However, disparate levels of neuronal dopamine and serotonin during development of the circuit result in abnormal gut fiber architecture and feeding behavior. CONCLUSIONS These results suggest that dopamine can exert a direct trophic influence on the development of a specific neural circuit, and that dopamine and serotonin may interact with each other to generate the neural architecture necessary for normal function of the circuit.
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Affiliation(s)
- Wendi S Neckameyer
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, 1402 South Grand Boulevard, Saint Louis, Missouri 63104, USA
| | - Parag Bhatt
- Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, 1402 South Grand Boulevard, Saint Louis, Missouri 63104, USA
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10
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Fava GA, Offidani E. The mechanisms of tolerance in antidepressant action. Prog Neuropsychopharmacol Biol Psychiatry 2011; 35:1593-602. [PMID: 20728491 DOI: 10.1016/j.pnpbp.2010.07.026] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Revised: 07/27/2010] [Accepted: 07/27/2010] [Indexed: 12/28/2022]
Abstract
There is increasing awareness that, in some cases, long-term use of antidepressant drugs (AD) may enhance the biochemical vulnerability to depression and worsen its long-term outcome and symptomatic expression, decreasing both the likelihood of subsequent response to pharmacological treatment and the duration of symptom-free periods. A review of literature suggesting potential side effects during long treatment with antidepressant drugs was performed. Studies were identified electronically using the following databases: Medline, Cinahl, PsychInfo, Web of Science and the Cochrane Library. Each database was searched from its inception date to April 2010 using "tolerance", "withdrawal", "sensitization", "antidepressants" and "switching" as key words. Further, a manual search of the psychiatric literature has been performed looking for articles pointing to paradoxical effects of antidepressant medications. Clinical evidence has been found indicating that even though antidepressant drugs are effective in treating depressive episodes, they are less efficacious in recurrent depression and in preventing relapse. In some cases, antidepressants have been described inducing adverse events such as withdrawal symptoms at discontinuation, onset of tolerance and resistance phenomena and switch and cycle acceleration in bipolar patients. Unfavorable long-term outcomes and paradoxical effects (depression inducing and symptomatic worsening) have also been reported. All these phenomena may be explained on the basis of the oppositional model of tolerance. Continued drug treatment may recruit processes that oppose the initial acute effect of a drug. When drug treatment ends, these processes may operate unopposed, at least for some time and increase vulnerability to relapse. Antidepressant drugs are crucial in the treatment of major depressive episodes. However, appraisal and testing of the oppositional model of tolerance may yield important insights as to long-term treatment and achievement of enduring effects.
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Affiliation(s)
- Giovanni A Fava
- Affective Disorders Program, Department of Psychology, University of Bologna, Bologna, Italy.
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11
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Benton JL, Zhang Y, Kirkhart CR, Sandeman DC, Beltz BS. Primary neuronal precursors in adult crayfish brain: replenishment from a non-neuronal source. BMC Neurosci 2011; 12:53. [PMID: 21635768 PMCID: PMC3127996 DOI: 10.1186/1471-2202-12-53] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 06/02/2011] [Indexed: 12/12/2022] Open
Abstract
Background Adult neurogenesis, the production and integration of new neurons into circuits in the brains of adult animals, is a common feature of a variety of organisms, ranging from insects and crustaceans to birds and mammals. In the mammalian brain the 1st-generation neuronal precursors, the astrocytic stem cells, reside in neurogenic niches and are reported to undergo self-renewing divisions, thereby providing a source of new neurons throughout an animal's life. In contrast, our work shows that the 1st-generation neuronal precursors in the crayfish (Procambarus clarkii) brain, which also have glial properties and lie in a neurogenic niche resembling that of vertebrates, undergo geometrically symmetrical divisions and both daughters appear to migrate away from the niche. However, in spite of this continuous efflux of cells, the number of neuronal precursors in the crayfish niche continues to expand as the animals grow and age. Based on these observations we have hypothesized that (1) the neuronal stem cells in the crayfish brain are not self-renewing, and (2) a source external to the neurogenic niche must provide cells that replenish the stem cell pool. Results In the present study, we tested the first hypothesis using sequential double nucleoside labeling to track the fate of 1st- and 2nd-generation neuronal precursors, as well as testing the size of the labeled stem cell pool following increasing incubation times in 5-bromo-2'-deoxyuridine (BrdU). Our results indicate that the 1st-generation precursor cells in the crayfish brain, which are functionally analogous to neural stem cells in vertebrates, are not a self-renewing population. In addition, these studies establish the cycle time of these cells. In vitro studies examining the second hypothesis show that Cell Tracker™ Green-labeled cells extracted from the hemolymph, but not other tissues, are attracted to and incorporated into the neurogenic niche, a phenomenon that appears to involve serotonergic mechanisms. Conclusions These results challenge our current understanding of self-renewal capacity as a defining characteristic of all adult neuronal stem cells. In addition, we suggest that in crayfish, the hematopoietic system may be a source of cells that replenish the niche stem cell pool.
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Affiliation(s)
- Jeanne L Benton
- Neuroscience Program, Wellesley College, 106 Central Street, Wellesley, MA 02481, USA
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12
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Wollesen T, Degnan BM, Wanninger A. Expression of serotonin (5-HT) during CNS development of the cephalopod mollusk, Idiosepius notoides. Cell Tissue Res 2010; 342:161-78. [PMID: 20976473 DOI: 10.1007/s00441-010-1051-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 08/18/2010] [Indexed: 10/18/2022]
Abstract
Cephalopods are unique among mollusks in exhibiting an elaborate central nervous system (CNS) and remarkable cognitive abilities. Despite a profound knowledge of the neuroanatomy and neurotransmitter distribution in their adult CNS, little is known about the expression of neurotransmitters during cephalopod development. Here, we identify the first serotonin-immunoreactive (5-HT-ir) neurons during ontogeny and describe the establishment of the 5-HT system in the pygmy squid, Idiosepius notoides. Neurons that are located dorsally to each optic lobe are the first to express 5-HT, albeit only when the lobular neuropils are already quite elaborated. Later, 5-HT is expressed in almost all lobes, with most 5-HT-ir cell somata appearing in the subesophageal mass. Further lobes with numerous 5-HT-ir cell somata are the subvertical and posterior basal lobes and the optic and superior buccal lobes. Hatching squids possess more 5-HT-ir neurons, although the proportions between the individual brain lobes remain the same. The majority of 5-HT-ir cell somata appears to be retained in the adult CNS. The overall distribution of 5-HT-ir elements within the CNS of adult I. notoides resembles that of adult Octopus vulgaris and Sepia officinalis. The superior frontal lobe of all three species possesses few or no 5-HT-ir cell somata, whereas the superior buccal lobe comprises many cell somata. The absence of 5-HT-ir cell somata in the inferior buccal lobes of cephalopods and the buccal ganglia of gastropods may constitute immunochemical evidence of their homology. This integrative work forms the basis for future studies comparing molluscan, lophotrochozoan, ecdysozoan, and vertebrate brains.
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Affiliation(s)
- Tim Wollesen
- Research Group for Comparative Zoology, Department of Biology, University of Copenhagen, 2100, Copenhagen, Denmark
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13
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Serotonin: a regulator of neuronal morphology and circuitry. Trends Neurosci 2010; 33:424-34. [PMID: 20561690 DOI: 10.1016/j.tins.2010.05.005] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 05/17/2010] [Accepted: 05/18/2010] [Indexed: 11/22/2022]
Abstract
Serotonin is an important neuromodulator associated with a wide range of physiological effects in the central nervous system. The exact mechanisms whereby serotonin influences brain development are not well understood, although studies in invertebrate and vertebrate model organisms are beginning to unravel a regulatory role for serotonin in neuronal morphology and circuit formation. Recent data suggest a developmental window during which altered serotonin levels permanently influence neuronal circuitry, however, the temporal constraints and molecular mechanisms responsible are still under investigation. Growing evidence suggests that alterations in early serotonin signaling contribute to a number of neurodevelopmental and neuropsychiatric disorders. Thus, understanding how altered serotonin signaling affects neuronal morphology and plasticity, and ultimately animal physiology and pathophysiology, will be of great significance.
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Szabo TM, Caplan JS, Zoran MJ. Serotonin regulates electrical coupling via modulation of extrajunctional conductance: H-current. Brain Res 2010; 1349:21-31. [PMID: 20599836 DOI: 10.1016/j.brainres.2010.06.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 05/03/2010] [Accepted: 06/10/2010] [Indexed: 12/30/2022]
Abstract
Synaptic strength can be highly variable from animal to animal within a species or over time within an individual. The process of synaptic plasticity induced by neuromodulatory agents might be unpredictable when the underlying circuits subject to modulation are themselves inherently variable. Serotonin (5-hydroxytryptomine; 5HT) and serotonergic signaling pathways are important regulators of animal behavior and are pharmacological targets in a wide range of neurological disorders. We have examined the effect of 5HT on electrical synapses possessing variable coupling strengths. While 5HT decreased electrical coupling at synapses with weak electrical connectivity, synapses with strong electrical coupling were less affected by 5HT treatment, as follows from the equations used for calculating coupling coefficients. The fact that the modulatory effect of 5HT on electrical connections was negatively correlated with the strength of electrical coupling suggests that the degree of electrical coupling within a neural network impacts subsequent neuromodulation of those synapses. Biophysical studies indicated that these effects were primarily due to 5HT-induced modulation of membrane currents that indirectly affect junctional coupling at synaptic contacts. In support of these experimental analyses, we created a simple model of coupled neurons to demonstrate that modulation of electrical coupling could be due solely to 5HT effects on H-channel conductance. Therefore, variability in the strength of electrical coupling in neural circuits can determine the pharmacological effect of this neuromodulatory agent.
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Affiliation(s)
- Theresa M Szabo
- Department of Biology, Brandeis University, Waltham, MA 02453, USA
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15
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Hiripi L, Elekes K. A 5-HT1A-like receptor is involved in the regulation of the embryonic rotation of Lymnaea stagnalis L. Comp Biochem Physiol C Toxicol Pharmacol 2010; 152:57-61. [PMID: 20188856 DOI: 10.1016/j.cbpc.2010.02.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Revised: 02/19/2010] [Accepted: 02/19/2010] [Indexed: 10/19/2022]
Abstract
Cilia driven rotation of the pond snail Lymnaea stagnalis embryos is regulated by serotonin (5-HT). In the present study, physiological and biochemical assays were used to identify the 5-HT receptor type involved in rotation. The 5-HTergic agonists applied stimulated the rotation by 180-400% and their rank order potency was as follows: LSD>5-HT>8-OH-DPAT>WB4101>>5-CT. The applied antagonists, spiperone, propranalol and mianserin inhibited the 5-HT or 8-OH-DPAT stimulated rotation of the embryos by 50-70%. (3)H-5-HT was bound specifically to the washed pellet of the embryo homogenates. The specific binding of (3)H-5-HT was saturable and showed a single, high affinity binding site with K(d) 7.36 nM and B(max) 221 fmol/mg pellet values. This is the first report demonstrating the high affinity binding of (3)H-5-HT to the native receptor in molluscs. All of the pharmacons that stimulated the rotation or inhibited the 5-HT or 8-OH-DPAT evoked stimulation displaced effectively the binding of (3)H-5-HT. 5-HT resulted in the inhibition of forskolin stimulated cAMP accumulation, showing that 5-HT is negatively coupled to adenylate cyclase. Our results suggest that in the 5-HTergic regulation of the embryonic rotation in L. stagnalis a 5-HT(1A)-like receptor of the vertebrate type is involved.
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Affiliation(s)
- László Hiripi
- Department of Experimental Zoology, Balaton Limnological Research Institute, Hungarian Academy of Sciences, H-8237 Tihany, P.O.B. 35, Hungary.
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16
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Serotonergic dystrophy induced by excess serotonin. Mol Cell Neurosci 2010; 44:297-306. [PMID: 20394820 DOI: 10.1016/j.mcn.2010.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 03/18/2010] [Accepted: 04/02/2010] [Indexed: 01/15/2023] Open
Abstract
Administration of certain serotonin-releasing amphetamine derivatives (fenfluramine and/or 3,4-methylenedioxymethamphetamine, MDMA, 'ecstasy') results in dystrophic serotonergic morphology in the mammalian brain. In addition to drug administration, dystrophic serotonergic neurites are also associated with neurodegenerative disorders. We demonstrate here that endogenously elevated serotonin in the Drosophila CNS induces aberrant enlarged varicosities, or spheroids, that are morphologically similar to dystrophic mammalian serotonergic fibers. In Drosophila these spheroids are specific to serotonergic neurons, distinct from typical varicosities, and form only after prolonged increases in cytoplasmic serotonin. Our results also suggest that serotonin levels during early development determine later sensitivity of spheroid formation to manipulations of the serotonin transporter (SERT). Elevated serotonin also interacts with canonical protein aggregation and autophagic pathways to form spheroids. The data presented here support a model in which excess cytoplasmic neurotransmitter triggers a cell-specific pathway inducing aberrant morphology in fly serotonergic neurons that may be shared in certain mammalian pathologies.
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Filla A, Hiripi L, Elekes K. Role of aminergic (serotonin and dopamine) systems in the embryogenesis and different embryonic behaviors of the pond snail, Lymnaea stagnalis. Comp Biochem Physiol C Toxicol Pharmacol 2009; 149:73-82. [PMID: 18682301 DOI: 10.1016/j.cbpc.2008.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 07/08/2008] [Accepted: 07/08/2008] [Indexed: 11/17/2022]
Abstract
A detailed biochemical and pharmacological analysis of the dopaminergic (DAergic) and serotonergic (5-HTergic) systems was performed during the embryogenesis of Lymnaea stagnalis, to monitor their role in development and different behaviors. The dopamine (DA) level and the synthesizing decarboxylase enzyme activity showed a continuous increase, whereas the serotonin (5-HT) concentration remained low until late postmetamorphic development, when they all showed a rapid and significant increase. Application of monoamine precursors increased, whereas enzyme inhibitors and neurotoxins reduced monoamine levels; all treatments resulting in a prolongation of embryogenesis. Following, p-chlorphenylalanine (pCPA) and 3-hydroxybenzylhydrazine (Nsd-1015) treatments, no 5-HT immunoreactivity could be detected in the embryonic nervous system. These findings suggest that changes of monoamine levels in either (negative or positive) direction cause slowing of embryogenesis. Embryonic rotation and radula protrusion rate was enhanced following both serotonin and dopamine application, whereas frequency of gliding was increased by serotonin treatment. These results clearly indicate the involvement of 5-HT and DA in the regulation of a broad range of embryonic behaviors. Pharmacological characterization of a 5-HT receptor associated with the L. stagnalis embryonic behaviors studied revealed that a mammalian 5-HT(1)-like receptor type is involved in the 5-HTergic regulation of locomotion activity.
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Affiliation(s)
- Adrienn Filla
- Department of Experimental Zoology, Balaton Limnological Research Institute, Hungarian Academy of Science, Tihany, Hungary
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Mapara S, Parries S, Quarrington C, Ahn KC, Gallin WJ, Goldberg JI. Identification, molecular structure and expression of two cloned serotonin receptors from the pond snail, Helisoma trivolvis. ACTA ACUST UNITED AC 2008; 211:900-10. [PMID: 18310116 DOI: 10.1242/jeb.013953] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Helisoma trivolvis has served as a model system to study the functions of serotonin (5-HT) from cellular, developmental, physiological and behavioural perspectives. To further explore the serotonin system at the molecular level, and to provide experimental knockout tools for future studies, in this study we identified serotonin receptor genes from the H. trivolvis genome, and characterized the molecular structure and expression profile of the serotonin receptor gene products. Degenerate oligonucleotide primers, based on conserved regions of the Lymnaea stagnalis 5-HT(1Lym) receptor, were used to amplify G protein-coupled biogenic amine receptor sequences from H. trivolvis genomic cDNA, resulting in the cloning of two putative serotonin receptors. The deduced gene products both appear to be G protein-coupled serotonin receptors, with well-conserved structure in the functional domains and high variability in the vestibule entrance of the receptor protein. Phylogenetic analysis placed these receptors in the 5-HT(1) and 5-HT(7) families of serotonin receptors. They are thus named the 5-HT(1Hel) and 5-HT(7Hel) receptors, respectively. In situ hybridization and immunofluorescence studies revealed that these genes and gene products are expressed most heavily in the ciliated pedal and mantle epithelia of H. trivolvis embryos. In adults, widespread expression occurred in all ganglia and connectives of the central nervous system. Expression of both receptor proteins was localized exclusively to neurites when examined in situ. In contrast, when isolated neurons were grown in culture, 5-HT(1Hel) and 5-HT(7Hel) immunoreactivity were located primarily in the cell body. This is the first study to reveal a 5-HT(7) receptor in a molluscan species.
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Affiliation(s)
- Sabeen Mapara
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
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Calviño MA, Szczupak L. Spatial-specific action of serotonin within the leech midbody ganglion. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2008; 194:523-31. [PMID: 18365206 DOI: 10.1007/s00359-008-0326-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Revised: 02/26/2008] [Accepted: 03/07/2008] [Indexed: 10/22/2022]
Abstract
Serotonin is a conspicuous neuromodulator in the nervous system of many vertebrates and invertebrates. In previous experiments performed in the leech nervous system, we compared the effect of the amine released from endogenous sources [using selective serotonin reuptake inhibitors (SSRIs), e.g. fluoxetine] with that of bath-applied serotonin. The results suggested that the amine does not reach all its targets in a uniform way, but produces the activation of an interneuronal pathway that generated specific synaptic responses on different neurons. Taking into account that the release of the amine is often regulated at the presynaptic level, we have investigated whether autoreceptor antagonists mimic the SSRIs effect. We found that methiothepin (100 microM) produced similar effects than fluoxetine. To further test the hypothesis that endogenous serotonin produce its effect by acting locally at specific sites, we analyzed the effect of iontophoretic applications of serotonin. We found a site in the neuropil of the leech ganglia where serotonin application mimicked the effect of the SSRIs and the 5-HT antagonist. The results further support the view that the effect of serotonin exhibits a spatial specificity that can be relevant to understand its modulatory actions.
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Affiliation(s)
- María Ana Calviño
- Dto. de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IFIBYNE-CONICET, Ciudad Universitaria, Pabellón II, piso 2, 1428 Buenos Aires, Argentina.
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Airhart MJ, Lee DH, Wilson TD, Miller BE, Miller MN, Skalko RG. Movement disorders and neurochemical changes in zebrafish larvae after bath exposure to fluoxetine (PROZAC). Neurotoxicol Teratol 2007; 29:652-64. [PMID: 17761399 DOI: 10.1016/j.ntt.2007.07.005] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 06/21/2007] [Accepted: 07/06/2007] [Indexed: 01/01/2023]
Abstract
This study examines the effects of the selective serotonin reuptake inhibitor (SSRI), fluoxetine (PROZAC), on the ontogeny of spontaneous swimming activity (SSA) in developing zebrafish. The development of zebrafish motor behavior consists of four sequential locomotor patterns that develop over 1-5 days post fertilization (dpf), with the final pattern, SSA, established at 4-5 dpf. In stage specific experiments, larvae were exposed to 4.6 microM fluoxetine for 24 h periods beginning at 24 h post fertilization (hpf) and extending through 5 dpf. From 1-3 dpf, there was no effect on SSA or earlier stages of motor development, i.e., spontaneous coiling, evoked coiling and burst swimming. Fluoxetine exposure at 3 dpf for 24 h resulted in a transient decrease in SSA through 7 dpf with a complete recovery by 8 dpf. Larvae exposed to 4.6 microM fluoxetine for 24 h on 4 or 5 dpf showed a significant decrease in SSA by day 6 with no recovery through 14 dpf. Although SSA was significantly affected 24 h after fluoxetine exposure, there was little or no effect on pectoral fin movement. These results demonstrate both a stage specific and a long term effect of 4.6 microM fluoxetine exposure in 4 and 5 dpf larvae. Reverse transcriptase polymerase chain reaction (RT-PCR) was performed to determine the relative levels of a serotonin transporter protein (SERT) transcript and the serotonin 1A (5-HT(1A)) receptor transcript in developing embryos/larvae over 1-6 dpf. Both transcripts were present at 24 hpf with the relative concentration of SERT transcript showing no change over the developmental time range. The relative concentration of the 5-HT(1A) receptor transcript, however, showed a two-tiered pattern of concentration. RT-PCR was also used to detect potential changes in the SERT and 5-HT(1A) receptor transcripts in 6 dpf larvae after a 24 h exposure to 4.6 microM fluoxetine on 5 dpf. Three separate regions of the CNS were individually analyzed, two defined brain regions and spinal cord. The two brain regions showed no effect on transcript levels subsequent to fluoxetine exposure, however, the spinal cord showed a significant decrease in both transcripts. These results suggest a correlation between decreased concentration of SERT and 5-HT(1A) receptor transcripts in spinal cord and decreased SSA subsequent to fluoxetine exposure.
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Affiliation(s)
- Mark J Airhart
- Department of Anatomy and Cell Biology, P.O. Box 70582, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614-1708, USA.
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Roy B, Singh AP, Shetty C, Chaudhary V, North A, Landgraf M, Vijayraghavan K, Rodrigues V. Metamorphosis of an identified serotonergic neuron in the Drosophila olfactory system. Neural Dev 2007; 2:20. [PMID: 17958902 PMCID: PMC2129096 DOI: 10.1186/1749-8104-2-20] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 10/24/2007] [Indexed: 11/23/2022] Open
Abstract
Background Odors are detected by sensory neurons that carry information to the olfactory lobe where they connect to projection neurons and local interneurons in glomeruli: anatomically well-characterized structures that collect, integrate and relay information to higher centers. Recent studies have revealed that the sensitivity of such networks can be modulated by wide-field feedback neurons. The connectivity and function of such feedback neurons are themselves subject to alteration by external cues, such as hormones, stress, or experience. Very little is known about how this class of central neurons changes its anatomical properties to perform functions in altered developmental contexts. A mechanistic understanding of how central neurons change their anatomy to meet new functional requirements will benefit greatly from the establishment of a model preparation where cellular and molecular changes can be examined in an identified central neuron. Results In this study, we examine a wide-field serotonergic neuron in the Drosophila olfactory pathway and map the dramatic changes that it undergoes from larva to adult. We show that expression of a dominant-negative form of the ecdysterone receptor prevents remodeling. We further use different transgenic constructs to silence neuronal activity and report defects in the morphology of the adult-specific dendritic trees. The branching of the presynaptic axonal arbors is regulated by mechanisms that affect axon growth and retrograde transport. The neuron develops its normal morphology in the absence of sensory input to the antennal lobe, or of the mushroom bodies. However, ablation of its presumptive postsynaptic partners, the projection neurons and/or local interneurons, affects the growth and branching of terminal arbors. Conclusion Our studies establish a cellular system for studying remodeling of a central neuromodulatory feedback neuron and also identify key elements in this process. Understanding the morphogenesis of such neurons, which have been shown in other systems to modulate the sensitivity and directionality of response to odors, links anatomy to the development of olfactory behavior.
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Affiliation(s)
- Bidisha Roy
- National Centre for Biological Sciences, TIFR, GKVK PO, Bangalore 560065, India.
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Stern M, Knipp S, Bicker G. Embryonic differentiation of serotonin-containing neurons in the enteric nervous system of the locust (Locusta migratoria). J Comp Neurol 2007; 501:38-51. [PMID: 17206618 DOI: 10.1002/cne.21235] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The enteric nervous system (ENS) of the locust consists of four ganglia (frontal and hypocerebral ganglion, and the paired ingluvial ganglia) located on the foregut, and nerve plexus innervating fore- and midgut. One of the major neurotransmitters of the ENS, serotonin, is known to play a vital role in gut motility and feeding. We followed the anatomy of the serotonergic system throughout embryonic development. Serotonergic neurons are generated in the anterior neurogenic zones of the foregut and migrate rostrally along the developing recurrent nerve to contribute to the frontal ganglion. They grow descending neurites, which arborize in all enteric ganglia and both nerve plexus. On the midgut, the neurites closely follow the leading migrating midgut neurons. The onset of serotonin synthesis occurs around halfway through development-the time of the beginning of midgut closure. Cells developing to serotonergic phenotype express the serotonin uptake transporter (SERT) significantly earlier, beginning at 40% of development. The neurons begin SERT expression during migration along the recurrent nerve, indicating that they are committed to a serotonergic phenotype before reaching their final destination. After completion of the layout of the enteric ganglia (at 60%) a maturational phase follows, during which serotonin-immunoreactive cell bodies increase in size and the fine arborizations in the nerve plexus develop varicosities, putative sites of serotonin release (at 80%). This study provides the initial step for future investigation of potential morphoregulatory functions of serotonin during ENS development.
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Affiliation(s)
- Michael Stern
- Cell Biology, Institute of Physiology, University of Veterinary Medicine Hannover, D-30173 Hannover, Germany.
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WHITAKER-AZMITIA PATRICIAM. Role of the Neurotrophic Properties of Serotonin in the Delay of Brain Maturation Induced by Cocainea. Ann N Y Acad Sci 2006; 846:158-164. [DOI: 10.1111/j.1749-6632.1998.tb09734.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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24
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Koza A, Wilhelm M, Hiripi L, Elekes K, Csoknya M. Embryogenesis of the serotonergic system in the earthwormEisenia fetida (Annelida, Oligochaeta): Immunohistochemical and biochemical studies. J Comp Neurol 2006; 497:451-67. [PMID: 16736470 DOI: 10.1002/cne.21008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Organization of the serotonergic system and changes of the serotonin (5-HT) content were studied during the embryogenesis of the earthworm Eisenia fetida, using immunocytochemistry and HPLC. A gradual emergence of 5-HT immunoreactive (IR) cells and their axon projections in the several ganglia of the central (CNS) and peripheral nervous system are described in the context of a staged time-scale of development. The first 5-HT-IR neurons appear in the subesophageal ganglion at an early embryonic stage (E2), followed by neurons in some rostrally located ventral ganglia. In the cerebral ganglion, 5-HT-IR cells can be detected only from stage E5. The number of labeled cells in each ganglion of the embryo increases until hatching, when it is still considerably lower than that observed in adults. This shows that the development of the 5-HTergic system is far from complete by the end of embryogenesis. Organization of 5-HT-IR innervation of the body wall starts by stages E3 to E4. In the stomatogastric nervous system the first 5-HT-IR fibers can be detected by stage E5. By stage E9 5-HT immunopositive neurons can be observed in both the stomatogastric ganglia and the enteric plexus. Both 5-HT levels and the numbers of the labeled cells show a significant increase before hatching, which indicate a functional maturation of the 5-HTergic system. Based on the early appearance of 5-HT, we suppose that it may play a regulatory role in both the gangliogenesis and the maturation of peripheral functions necessary during postembryonic life.
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Affiliation(s)
- Anna Koza
- MTA-PTE Adaptation Biology Research Group, University of Pécs, Pécs, Hungary
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25
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Sykes PA, Condron BG. Development and sensitivity to serotonin of Drosophila serotonergic varicosities in the central nervous system. Dev Biol 2005; 286:207-16. [PMID: 16122730 PMCID: PMC2896038 DOI: 10.1016/j.ydbio.2005.07.025] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 07/18/2005] [Accepted: 07/20/2005] [Indexed: 10/25/2022]
Abstract
Serotonin is a classical small-molecule neurotransmitter with known effects on developmental processes. Previous studies have shown a developmental role for serotonin in the fly peripheral nervous system. In this study, we show that serotonin can modulate the development of serotonergic varicosities within the fly central nervous system. We have developed a system to examine the development of serotonergic varicosities in the larval CNS. We use this method to describe the normal serotonergic development in the A7 abdominal ganglion. From first to third instar larvae, the volume of the neuropil and number of serotonergic varicosities increase substantially while the varicosity density remains relatively constant. We hypothesize that serotonin is an autoregulator for serotonergic varicosity density. We tested the sensitivity of serotonergic varicosities to serotonin by adding neurotransmitter at various stages to isolated larval ventral nerve cords. Addition of excess exogenous serotonin decreases native varicosity density in older larvae, and these acute effects are reversible. The effects of serotonin appear to be selective for serotonergic varicosities, as dopaminergic and corazonergic varicosities remain qualitatively intact following serotonin application.
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Affiliation(s)
- Paul A. Sykes
- University of Virginia Medical Scientist Training Program, Charlottesville, VA 22903, USA
- Department of Biology, University of Virginia, Gilmer Hall 071, Box 400328, Charlottesville, VA 22903, USA
| | - Barry G. Condron
- Department of Biology, University of Virginia, Gilmer Hall 071, Box 400328, Charlottesville, VA 22903, USA
- Corresponding author. Fax: +1 434 243 5315. (B.G. Condron)
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26
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Voronezhskaya EE, Khabarova MY, Nezlin LP. Apical sensory neurones mediate developmental retardation induced by conspecific environmental stimuli in freshwater pulmonate snails. Development 2004; 131:3671-80. [PMID: 15229179 DOI: 10.1242/dev.01237] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Freshwater pond snails Helisoma trivolvis and Lymnaea stagnalis undergo larval development and metamorphosis inside egg capsules. We report that their development is permanently under slight tonic inhibitory influence of the anterior sensory monoaminergic neurones, which are the remnants of the apical sensory organ. Conspecific juvenile snails, when reared under conditions of starvation and crowding, release chemical signals that are detected by these neurones in encapsulated larvae and reversibly suppress larval development, thus providing a link between environmental signals and developmental regulation. Induced retardation starts from the trochophore stage and results in up to twofold prolongation of the larval lifespan. Upon stimulation with the signal, the neurones increase synthesis and release of monoamines [serotonin (5-HT) in Helisoma and dopamine in Lymnaea] that inhibit larval development acting via ergometrine-sensitive internal receptors. Thus, the novel regulatory mechanism in larval development of molluscs is suggested and compared with the phenomenon of dauer larvae formation in the nematode Caenorhabditis elegans.
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Affiliation(s)
- Elena E Voronezhskaya
- Institute of Developmental Biology, Russian Academy of Science, Moscow 117808, Russia
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Spitzer NC, Root CM, Borodinsky LN. Orchestrating neuronal differentiation: patterns of Ca2+ spikes specify transmitter choice. Trends Neurosci 2004; 27:415-21. [PMID: 15219741 DOI: 10.1016/j.tins.2004.05.003] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Appropriate specification of neurotransmitters is a key feature of neuronal network assembly. There is much evidence that genetic programs are responsible for this aspect of cell fate and neuronal differentiation. Are there additional ways in which these processes are shaped? Recent findings demonstrate that altering patterned Ca(2+) spike activity that is spontaneously generated by different classes of embryonic spinal neurons in vivo changes expression of neurotransmitters in a homeostatic manner, as if to achieve a constant level of excitation. Activity-dependent changes in presynaptic transmitter expression pose a matching problem: are there corresponding changes in postsynaptic transmitter receptor expression, or are axons rerouted to novel targets with which functional synapses can be formed?
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Affiliation(s)
- Nicholas C Spitzer
- Neurobiology Section and Center for Molecular Genetics, Division of Biological Sciences, UCSD, La Jolla, CA 92093, USA.
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28
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Borodinsky LN, Root CM, Cronin JA, Sann SB, Gu X, Spitzer NC. Activity-dependent homeostatic specification of transmitter expression in embryonic neurons. Nature 2004; 429:523-30. [PMID: 15175743 DOI: 10.1038/nature02518] [Citation(s) in RCA: 297] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 03/29/2004] [Indexed: 11/08/2022]
Abstract
Neurotransmitters are essential for interneuronal signalling, and the specification of appropriate transmitters in differentiating neurons has been related to intrinsic neuronal identity and to extrinsic signalling proteins. Here we show that altering the distinct patterns of Ca2+ spike activity spontaneously generated by different classes of embryonic spinal neurons in vivo changes the transmitter that neurons express without affecting the expression of markers of cell identity. Regulation seems to be homeostatic: suppression of activity leads to an increased number of neurons expressing excitatory transmitters and a decreased number of neurons expressing inhibitory transmitters; the reverse occurs when activity is enhanced. The imposition of specific spike frequencies in vitro does not affect labels of cell identity but again specifies the expression of transmitters that are inappropriate for the markers they express, during an early critical period. The results identify a new role of patterned activity in development of the central nervous system.
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Affiliation(s)
- Laura N Borodinsky
- Neurobiology Section, Division of Biological Sciences and Center for Molecular Genetics, UCSD, La Jolla, California 92093-0357, USA.
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29
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Koza A, Csoknya M. Embryogenesis of GABAergic elements in the nervous system of Eisenia fetida (Annelida, Oligochaeta). ACTA BIOLOGICA HUNGARICA 2004; 55:323-33. [PMID: 15270249 DOI: 10.1556/abiol.55.2004.1-4.38] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The appearance and development of the GABA-immunoreactive nervous elements in the central nervous system of Eisenia fetida were studied by immunocytochemistry. The nervous system originates from the neuroectoderm situated on the ventral side of the embryo. The organization of the circumpharyngeal ring starts earlier than that of the ventral cord. In the elementary ring the first GABA-immunopositive neurons can be observed (E1 stage) around the mouth. Later the cell number gradually increases and parallel to this process the elementary ring is separeted into a superficial and a deeper portion. The brain and the subesophageal ganglion will be organized from the superficial ring, while the nervous elements of the deeper ring will give rise for the first GABA-immunoreactive elements of the stomatogastric nervous system. In the early stages of the embryogenesis the immunoreactive cells of the developing brain appear solitary, while from the stage E4 they gradually are observed in groups. According to their position, these cell groups are similar to those observed in the brain of the adult earthworms. During embryogenesis the level of the ventral cord ganglia depends on their position in the ectodermal germ bands. It means, that the more organized ganglia are near the circumpharyngeal ring, mean while less developed ganglia are situated caudally from them. By the end of the embryogenesis all ganglia of the ventral cord will be equally well organized. The nerve tracts of the ganglia are built up from contra- and ipsilateral by projected fibres. From E3 stage the medial tracts, mean while from the E4 stage the lateral tracts begin to be formed. During the next stages, more and more fibres connect to the both tracts. At hatching, the development of the central nervous system of Eisenia fetida is not completed, the process is continued during the postembryonic development.
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Affiliation(s)
- Anna Koza
- Department of General Zoology and Neurobiology, University of Pécs, Ifjúság u. 6, H-7624 Pécs, Hungary
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Beltz BS, Sandeman DC. Regulation of life-long neurogenesis in the decapod crustacean brain. ARTHROPOD STRUCTURE & DEVELOPMENT 2003; 32:39-60. [PMID: 18088995 DOI: 10.1016/s1467-8039(03)00038-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2003] [Accepted: 04/29/2003] [Indexed: 05/25/2023]
Abstract
This article provides an overview of our understanding of life-long neurogenesis in the decapod crustacean brain, where the proliferation of sensory and interneurons is controlled by many of the same factors as is neurogenesis in the mammalian brain. The relative simplicity, spatial organization and accessibility of the crustacean brain provide opportunities to examine specific neuronal pathways that regulate neurogenesis and the sequence of gene expression that leads to neuronal differentiation.
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Affiliation(s)
- Barbara S Beltz
- Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA
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Koss R, Diefenbach TJ, Kuang S, Doran SA, Goldberg JI. Coordinated development of identified serotonergic neurons and their target ciliary cells in Helisoma trivolvis embryos. J Comp Neurol 2003; 457:313-25. [PMID: 12561073 DOI: 10.1002/cne.10512] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Embryonic neuron C1s (ENC1s) are bilateral serotonergic neurons that function as cilioexcitatory motor neurons in embryonic development of the pond snail, Helisoma trivolvis. Recent experiments demonstrated that these neurons stimulate cilia-driven embryo rotation in response to hypoxia. In the present study, a comprehensive anatomic analysis of these cells and their target ciliary structures was done to address the following questions: (1) Does ENC1 have a morphology consistent with an oxygen-sensitive sensory cell; (2) Is the development of ENC1's neurite outgrowth pathway coordinated with the development of its target effectors, the pedal and dorsolateral ciliary bands; and (3) What is the anatomic basis of ENC1-ciliary communication? By using an array of microscopic techniques on live and serotonin-immunostained embryos, we found that each ENC1 possessed an apical dendrite that was capped with an integral dendritic knob penetrating the embryo surface. The dendritic knobs contained both microvilli and nonmotile cilia that suggested a sensory transduction role. Each ENC1 also possessed a descending projection, whose development was characterized by the rapid formation of the primary neurite pathway between stages E13 and E15, with the primary neurite of the right ENC1 developing in advance of its contralateral homologue. Secondary neurite branches formed between stages E15 and E30 in a spatiotemporal pattern that closely matched the development of the dorsolateral and pedal bands of cilia. Both dorsolateral and pedal ciliated cells formed basal processes that contacted ENC1 neurites. Finally, gap junction profiles were observed at neurite-neurite, neurite-ciliary cell, and ciliary cell-ciliary cell apposition sites, whereas putative chemical synaptic profiles were observed at neurite-neurite and neurite-ciliary cell apposition sites.
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Affiliation(s)
- Ron Koss
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
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Richards KS, Simon DJ, Pulver SR, Beltz BS, Marder E. Serotonin in the developing stomatogastric system of the lobster, Homarus americanus. JOURNAL OF NEUROBIOLOGY 2003; 54:380-92. [PMID: 12500313 DOI: 10.1002/neu.10136] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We studied the development of the serotonergic modulation of the stomatogastric nervous system of the lobster, Homarus americanus. Although the stomatogastric ganglion (STG) is present early in embryonic development, serotonin immunoreactivity is not visible in the STG until the second larval stage. However, incubation of the STG with exogenous serotonin showed that a serotonin transporter is present in embryonic and early larval stages. Serotonin uptake was blocked by paroxetine and 0% Na(+) saline. The presence of a serotonin transporter in the embryonic STG suggests that hormonally liberated serotonin could be taken up by the STG, and potentially released as a "borrowed transmitter". Consistent with a potential hormonal role, serotonin is found in the pericardial organs, a major neurosecretory structure, by midembryonic development. The rhythmic motor patterns produced by embryonic and larval STGs were decreased in frequency by serotonin. Lateral Pyloric (LP) neuron-evoked excitatory junctional potentials (EJPs) in the embryos and the first larval stage (LI) were larger, slower, and more variable than those in the adult. The amplitude of adult LP neuron-evoked EJPs was increased more than twofold in serotonin, but in embryos and LI preparations this effect was negligible. In embryos and LI preparations, serotonin increased the occurrence of muscle fiber action potentials and altered the EJP wave-form. These data demonstrate that serotonin receptors are present in the stomatogastric nervous system early in development, and suggest that the role of serotonin changes from modulation of muscle fiber excitability early in development to enhancement of neurally evoked EJPs in the adult.
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Affiliation(s)
- Kathryn S Richards
- Biology Department, Brandeis University, Waltham, Massachusetts 02454, USA
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Abstract
Besides a well-established role in neuronal communication in the adult central nervous system, neurotransmitters have diverse tasks in the embryonic brain, ranging from early developmental functions in morphogenesis /13/, to later functions in target selection and synapse formation /87/. For example, growth cones of developing neurons are known to release transmitters /26,36,88,110,115/ and respond to transmitters released from other neurons /35,44,59, 61,70/. Moreover, depletion of transmitters during embryonic development results in developmental deficits of the brain /21,48,84,109/, suggesting that transmitters have crucial roles as morphogens and/or neurotrophic factors. Although recently the idea of neurotransmitters being important for neural development has been challenged /99/, there is a vast amount of literature that seems to support the hypothesis that neurotransmitter release in the developing central nervous system is crucial for proper brain development. In this review we focus on the roles that neurotransmitters play in neurite outgrowth, target selection and synapse formation, with particular emphasis on the effects of the transmitters serotonin and dopamine.
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Affiliation(s)
- Ronald E van Kesteren
- Department of Molecular and Cellular Neurobiology, Faculty of Biology, Research Institute Neurosciences, Vrije Universiteit, Amsterdam, The Netherlands.
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Abstract
Brain development is a remarkable process. Progenitor cells are born, differentiate, and migrate to their final locations. Axons and dendrites branch and form important synaptic connections that set the stage for encoding information potentially for the rest of life. In the mammalian brain, synapses and receptors within most regions are overproduced and eliminated by as much as 50% during two phases of life: immediately before birth and during the transitions from childhood, adolescence, to adulthood. This process results in different critical and sensitive periods of brain development. Since Hebb (1949) first postulated that the strengthening of synaptic elements occurs through functional validation, researchers have applied this approach to understanding the sculpting of the immature brain. In this manner, the brain becomes wired to match the needs of the environment. Extensions of this hypothesis posit that exposure to both positive and negative elements before adolescence can imprint on the final adult topography in a manner that differs from exposure to the same elements after adolescence. This review endeavors to provide an overview of key components of mammalian brain development while simultaneously providing a framework for how perturbations during these changes uniquely impinge on the final outcome.
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Affiliation(s)
- Susan L Andersen
- Laboratory of Development Psychopharmocology, Department of Psychiatry, McLean Hospital and Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA.
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Nagy T, Elekes K. Ultrastructure of neuromuscular contacts in the embryonic pond snail Lymnaea stagnalis L. ACTA BIOLOGICA HUNGARICA 2002; 53:125-39. [PMID: 12064766 DOI: 10.1556/abiol.53.2002.1-2.13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ultrastructural characteristics of muscle fibers and neuromuscular contacts were investigated during two stages of embryogenesis of the pulmonate snail Lymnaea stagnalis. The first muscle cells appear as early as during metamorphosis (50-55% of embryonic development), whereas previously, in the trochophore/veliger stages (25-45%), muscular elements cannot be detected at all. The first muscle fibers contain large amounts of free numbers, a well-developed rER system and only a few irregularly arranged contractile elements. The nucleus is densely packed with heterochromatine material. At 75% adult-like postmetamorphic stage, the frequency of muscle fibers increases significantly, but, bundles of muscle fibers cannot yet be observed. Furthermore the muscle cells are characterized by large numbers of free ribosomes and numerous rER elements. Fine axon bundles and single axon processes, both accompanied by glial elements, can already be found at this time. Axon varicosities with different vesicle and/or granule contents form membrane contacts with muscle fibers, but without revealing membrane specialization on the pre- or postsynaptic side. The late development of the muscle system and neuromuscular contacts during Lymnaea embryogenesis correlates well with the maturation of different forms of behavior of adult, free-living life, and also with the peripheral appearance of chemically identified components of the embryonic nervous system of central origin.
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Affiliation(s)
- T Nagy
- Department of Experimental Zoology, Balaton Limnological Research Institute, Hungarian Academy of Sciences, Tihany
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36
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Cole AG, Mashkournia A, Parries SC, Goldberg JI. Regulation of early embryonic behavior by nitric oxide in the pond snail Helisoma trivolvis. J Exp Biol 2002; 205:3143-52. [PMID: 12235194 DOI: 10.1242/jeb.205.20.3143] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
SUMMARY
Helisoma trivolvis embryos display a cilia-driven rotational behavior that is regulated by a pair of serotonergic neurons named ENC1s. As these cilio-excitatory motor neurons contain an apical dendrite ending in a chemosensory dendritic knob at the embryonic surface, they probably function as sensorimotor neurons. Given that nitric oxide (NO) is often associated with sensory neurons in invertebrates, and has also been implicated in the control of ciliary activity, we examined the expression of NO synthase (NOS) activity and possible function of NO in regulating the rotational behavior in H. trivolvis embryos. NADPH diaphorase histochemistry on stage E25-E30 embryos revealed NOS expression in the protonephridia, buccal mass,dorsolateral ciliary cells and the sensory dendritic knobs of ENC1. At stages E35-40, the pedal ciliary cells and ENC1's soma, apical dendrite and proximal descending axon were also stained. In stage E25 embryos, optimal doses of the NO donors SNAP and SNP increased the rate of embryonic rotation by twofold, in contrast to the fourfold increase caused by 100 μmol l-1serotonin. The NOS inhibitors L-NAME (10 mmol l-1) and 7-NI (100μmol l-1) decreased the rotation rate by approximately 50%,whereas co-addition of L-NAME and SNAP caused a twofold increase. In an analysis of the surge and inter-surge subcomponents of the rotational behavior, the NO donors increased the inter-surge rotation rate and the surge amplitude. In contrast, the NO inhibitors decreased the inter-surge rotation rate and the frequency of surges. These data suggest that the embryonic rotational behavior depends in part on the constitutive excitatory actions of NO on ENC1 and ciliary cells.
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Affiliation(s)
- Alison G Cole
- Department of Biological Sciences, University of Alberta, Edmonton, Canada T6G 2E9
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PAGE LOUISER. Comparative structure of the larval apical sensory organ in gastropods and hypotheses about function and developmental evolution. INVERTEBR REPROD DEV 2002. [DOI: 10.1080/07924259.2002.9652752] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ponimaskin EG, Profirovic J, Vaiskunaite R, Richter DW, Voyno-Yasenetskaya TA. 5-Hydroxytryptamine 4(a) receptor is coupled to the Galpha subunit of heterotrimeric G13 protein. J Biol Chem 2002; 277:20812-9. [PMID: 11923294 DOI: 10.1074/jbc.m112216200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Serotonin (5-hydroxytryptamine (5-HT)) is an important neurotransmitter that regulates multiple events in the central nervous system. Many of the 5-HT functions are mediated via G protein-coupled receptors that are coupled to multiple heterotrimeric G proteins, including G(s), G(i), and G(q) subfamilies (Martin, G. R., Eglen, R. M., Hamblin, M. W., Hoyer, D., and Yocca, F. (1998) Trends Pharmacol. Sci. 19, 2-4). Here we show for the first time that the 5-hydroxytryptamine 4(a) receptor (5-HT(4(a))) is coupled not only to heterotrimeric G(s) but also to G(13) protein, as assessed both by biochemical and functional assays. Using reconstitution of 5-HT(4(a)) receptor with different G proteins in Spodoptera frugiperda (Sf.9) cells, we have proved that agonist stimulation of receptor-induced guanosine 5'-(3-O-thio)triphosphate binding to Galpha(13) protein. We then determined that expression of 5-HT(4(a)) receptor in mammalian cells induced constitutive- as well as agonist-promoted activation of a transcription factor, serum response element, through the activation of Galpha(13) and RhoA. Finally, we have determined that expression of 5-HT(4(a)) receptor in neuroblastoma x glioma NIE-115 cells cause RhoA-dependent neurite retraction and cell rounding under basal conditions and after agonist stimulation. These data suggest that by activating 5-HT(4(a)) receptor-G(13) pathway, serotonin plays a prominent role in regulating neuronal architecture in addition to its classical role in neurotransmission.
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Affiliation(s)
- Evgeni G Ponimaskin
- Abteilung Neuro- und Sinnesphysiologie, Physiologisches Institut Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany
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Page LR. Apical sensory organ in larvae of the patellogastropod Tectura scutum. THE BIOLOGICAL BULLETIN 2002; 202:6-22. [PMID: 11842011 DOI: 10.2307/1543218] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The apical sensory organ in veliger larvae of a patellogastropod, a basal clade of gastropod molluscs, was studied using ultrastructural and immunohistochemical techniques. Immediately before veligers of Tectura scutum undergo ontogenetic torsion, the apical sensory organ consists of three large cells that generate a very long apical ciliary tuft, two cells that generate a bilateral pair of shorter ciliary tufts, and a neural ganglion (apical ganglion). Putative sensory neurons forming the ganglion give rise to dendrites that extend to the apical surface of the larva and to basal neurites that contribute to a neuropil. The ganglion includes only one ampullary neuron, a distinctive neuronal type found in the apical ganglion of other gastropod veligers. Serotonin immunoreactivity is expressed by a medial and two lateral neurons, all having an apical dendrite, and also by neurites within the neuropil and by peripheral neurites that run beneath the ciliated prototrochal cells that power larval swimming. The three cells generating the long apical ciliary tuft are lost soon after ontogenetic torsion, and the medial serotonergic cell stops expressing serotonin antigenicity in late-stage veligers. The lateral ciliary tuft cells of T. scutum may be homologs of lateral ciliary tuft cells in planktotrophic opisthobranch veligers. A tripartite arrangement of sensory dendrites, as described previously for veligers of other gastropod clades, can be recognized in T. scutum after loss of the apical ciliary tuft cells.
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Affiliation(s)
- Louise R Page
- Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia, Canada V8W 3N5.
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40
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Abstract
Serotonin is known to play a role in brain development prior to the time it assumes its role as a neurotransmitter in the mature brain. Serotonin regulates both the development of serotonergic neurons (termed autoregulation of development) and the development of target tissues. In both cases, the astroglial-derived protein, S-100beta plays a role. Disruption of serotonergic development can leave permanent alterations in brain function and behavior. This may be the case in such human developmental illnesses as autism and Down Syndrome.
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Affiliation(s)
- P M Whitaker-Azmitia
- Program in Biopsychology, Department of Psychology, SUNY at Stony Brook, 11794-2500, USA.
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41
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Kreiling JA, Jessen-Eller K, Miller J, Seegal RF, Reinisch CL. Early development of the serotonergic and dopaminergic nervous system in Spisula solidissima (surf clam) larvae. Comp Biochem Physiol A Mol Integr Physiol 2001; 130:341-51. [PMID: 11544079 DOI: 10.1016/s1095-6433(01)00394-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We have defined the development of the serotonergic and dopaminergic components of the central nervous system in the early Spisula solidissima (surf clam) embryo using HPLC and immunocytochemistry. HPLC analysis reveals norepinephrine, dopamine, and serotonin are present at 24 h post-fertilization. Immunocytochemistry shows that the serotonergic nervous system emerges during the late trochophore stage with the development of a single serotonergic cell, C/A1, in the cerebral/apical ganglion. After 48 h, a second serotonergic cell forms, C/A2, which is connected to C/A1 by two serotonergic processes, and a single serotonergic cell emerges in the visceral ganglion, V1. At 72 h, a new serotonergic cell body develops in the cerebral/apical ganglion, C/A3. After 96 h, the cerebral/apical ganglion and visceral ganglion are connected by a serotonergic process. Expression of the dopamine receptor, D2, begins by 24 h with a generalized expression in the region of the developing gut. D2 expression in the gut ceases by 48 h. At 48 h, a network of fibers forms dorsolateral to the mouth. By 72 h, D2 expressing projections emerge from this network.
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Affiliation(s)
- J A Kreiling
- Marine Biological Laboratory, 7 MBL St., Woods Hole, MA 02540, USA
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Functional implications of neurotransmitter expression during axonal regeneration: serotonin, but not peptides, auto-regulate axon growth of an identified central neuron. J Neurosci 2001. [PMID: 11466431 DOI: 10.1523/jneurosci.21-15-05597.2001] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We studied the regenerative properties of one of two electrically coupled molluscan neurons, the serotonergic cerebral giant cells (CGCs) of Lymnaea stagnalis, after axotomy. The CGCs play a crucial role in feeding behavior, and when both cells are disconnected from their target neurons, animals no longer feed. When one CGC was permanently disconnected from its targets and the other was reversibly damaged by a nerve crush, the latter one regenerated over a period of 2 weeks to reform functional synapses with specific target neurons. At the same time, recovery of the feeding behavior was observed. After the crush, neuropeptide gene expression in the CGC was downregulated to approximately 50%. Serotonin synthesis, on the other hand, remained unaffected, suggesting that serotonin might have an active role in regeneration. In primary neuron culture, CGCs failed to extend neurites in the presence of serotonin; in cells that extended neurites in the absence of serotonin, focally applied serotonin, but not neuropeptides, induced growth cone collapse. Using serotonin-sensitive sniffer cells, we show that CGC neurites and growth cones release serotonin in culture. Finally, both the spontaneous and stimulation-induced release of serotonin from CGCs in culture resulted in growth cone collapse responses that could be blocked by the serotonin receptor antagonist methysergide. Our data suggest that auto-released serotonin is inhibitory to CGC neurite outgrowth in vitro. During regeneration in vivo, serotonin release might fine-tune axon guidance and branching by inducing local collapse responses in extending neurites.
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Kuang S, Goldberg JI. Laser ablation reveals regulation of ciliary activity by serotonergic neurons in molluscan embryos. JOURNAL OF NEUROBIOLOGY 2001; 47:1-15. [PMID: 11257609 DOI: 10.1002/neu.1011] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Early in embryonic development, the pond snail Helisoma trivolvis exhibits a rotational behavior that is generated by beating of cilia in the dorsolateral and pedal bands. Although previous anatomical and pharmacological studies provided indirect evidence that a pair of serotonergic neurons, Embryonic Neurons C1 (ENC1s), is involved in regulating embryonic rotation, direct evidence linking ENC1 to ciliary function is still lacking. In the present study, we used laser microbeams to perturb ENC1 in vivo while monitoring ciliary activity in identified ciliary bands. A laser treatment protocol to specifically ablate ENC1 without damaging the surrounding cells was established. Unilateral laser treatment of ENC1 caused transient increases in the activity of the pedal and ipsidorsolateral cilia, lasting 30-50 min. In contrast, activity of cilia that were not anatomically associated with ENC1 was unaffected by laser treatment. Mianserin, an effective serotonin antagonist in Helisoma ciliated cells, decreased the overall CBF of pedal and dorsolateral cilia by reducing the occurrence of spontaneous CBF surges in these cilia. Finally, the cilioexcitatory action of ENC1 laser treatment was mimicked by serotonin and reduced in the presence of mianserin. These results suggest that laser treatment provokes a release of serotonin from ENC1, resulting in a prolonged elevation of activity in the target ciliary cells. We conclude that, in addition to their previously established role in regulating neurodevelopment, ENC1s also function as serotonergic motor neurons to regulate ciliary activity, and therefore the rotational behavior of early embryos.
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Affiliation(s)
- S Kuang
- Department of Biological Sciences, University of Alberta, CW 405 Biological Science Building, Edmonton, Alberta, Canada T6G 2E9
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44
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Benton J, Beltz B. Effects of serotonin depletion on local interneurons in the developing olfactory pathway of lobsters. JOURNAL OF NEUROBIOLOGY 2001; 46:193-205. [PMID: 11169505 DOI: 10.1002/1097-4695(20010215)46:3<193::aid-neu1002>3.0.co;2-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
During embryonic life, the growth of the olfactory and accessory lobes of the lobster brain is retarded by serotonin depletion using 5,7-dihydroxytryptamine (5,7-DHT) (Benton et al., 1997). The local and projection interneurons that synapse with chemosensory cells in the olfactory lobes are potential targets of this depletion. This study documents proliferation and survival in the local interneuron cell clusters, and examines the differentiation of a prominent local interneuron, the serotonergic dorsal giant neuron (DGN), following serotonin depletion. An increase in dye coupling between the DGN and nearby cells is seen after serotonin depletion. However, morphometric analyses of individual DGNs in normal, sham-injected, and 5,7-DHT-treated embryos show that the general morphology and size of the DGNs are not significantly altered by serotonin depletion. Thus, the DGN axonal arbor occupies a greater proportion of the reduced olfactory lobes in the 5,7-DHT-treated embryos than in normal and sham-injected groups. The paired olfactory globular tract neutrophils (OGTNs), where olfactory interneurons synapse onto the DGNs, are 75% smaller in volume than the comparable region in either sham-injected or normal embryos. In vivo experiments using bromodeoxyuridine (BrdU) show that proliferation in the local interneuron soma clusters is reduced by 5,7-DHT treatment and that survival of newly proliferated local interneurons is also compromised. Our data suggest that alterations in the growth of the DGNs do not contribute to the dramatic reduction in size of the olfactory neutrophils following serotonin depletion, but that cell proliferation and survival among the local interneurons are regulated by serotonin during development. Reduced numbers of local interneurons are therefore one likely reason for the growth reduction observed after serotonin depletion.
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Affiliation(s)
- J Benton
- Department of Biological Sciences, Wellesley College, Wellesley, Massachusetts 02481, USA.
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45
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Frost DO, Cadet JL. Effects of methamphetamine-induced neurotoxicity on the development of neural circuitry: a hypothesis. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2000; 34:103-18. [PMID: 11113502 DOI: 10.1016/s0165-0173(00)00042-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Exposure of the developing brain to methamphetamine has well-studied biochemical and behavioral consequences. We review: (1) the effects of methamphetamine on mature serotonergic and dopaminergic pathways; (2) the mechanisms of methamphetamine neurotoxicity and (3) the role of serotonergic and dopaminergic signaling in sculpting developing neural circuitry. Consideration of these data suggest the types of neural circuit alterations that may result from exposure of the developing brain to methamphetamine and that may underlie functional defects.
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Affiliation(s)
- D O Frost
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, 655 West Baltimore St., Baltimore, MD 21201, USA.
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46
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Abstract
Gastropod research is providing many insights into mechanisms of neural regeneration. These observations were made possible by the pioneering work of individuals who described the nervous systems of gastropods, mapped prominent neurons and determined their roles and connections, and developed the techniques for culturing them. This information has allowed questions about injury responses, target selection, and pathway cues to be explored at the level of individually identified neurons. Because of gastropod studies, more is known about axon sealing, growth cone formation and behavior, signals that travel from the site of axotomy to the soma, and the second messengers that are activated there. The responses in neurons and non-neuronal cells during neural development and injury are coordinated by chemical messenger systems that are highly conserved, including neurotransmitters, cytokines, and neurotrophins. The nervous system is modified in learning paradigms by some of the same messenger systems activated by injury, because learning and injury both challenge neurons to change. The conservation of basic mechanisms that coordinate neuronal plasticity allows us to approach basic questions in relatively simple nervous systems with reasonable confidence that the findings will be relevant for other nervous systems, including possible applications to the mammalian nervous system.
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Affiliation(s)
- S B Moffett
- School of Biological Sciences, Washington State University, Pullman, Washington 99164, USA.
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47
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Abstract
The pattern of development of the serotonergic nervous system is described from the larvae of ctenophores, platyhelminths, nemerteans, entoprocts, ectoprocts (bryozoans), molluscs, polychaetes, brachiopods, phoronids, echinoderms, enteropneusts and lampreys. The larval brain (apical ganglion) of spiralian protostomes (except nermerteans) generally has three serotonergic neurons and the lateral pair always innervates the ciliary band of the prototroch. In contrast, brachiopods, phoronids, echinoderms and enteropneusts have numerous serotonergic neurons in the apical ganglion from which the ciliary band is innervated. This pattern of development is much like the pattern seen in lamprey embryos and larvae, which leads the author to conclude that the serotonergic raphe system found in vertebrates originated in the larval brain of deuterostome invertebrates. Further, the neural tube of chordates appears to be derived, at least in part, from the ciliary band of deuterostome invertebrate larvae. The evidence shows no sign of a shift in the dorsal ventral orientation within the line leading to the chordates.
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Affiliation(s)
- A Hay-Schmidt
- Department of Medical Anatomy B, The Panum Institute, University of Copenhagen, Denmark.
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48
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Santhanagopalan V, Yoshino TP. Monoamines and their metabolites in the freshwater snail Biomphalaria glabrata. Comp Biochem Physiol A Mol Integr Physiol 2000; 125:469-78. [PMID: 10840222 DOI: 10.1016/s1095-6433(00)00173-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Metabolism of the major monoamines and their functions were studied in the freshwater snail Biomphalaria glabrata. In both juvenile and adult snails, the plasma (cell-free hemolymph) appears to act as a reservoir for most of these monoamines and their metabolites including among others, L-dopa and dopamine as major constituents. Significant quantities of L-tryptophan, precursor of indoleamines, also was found in the plasma. L-dopa, serotonin, homovanillic acid and dopamine were prominently represented in the central nervous system of the snail, while serotonin and its metabolites, 5-hydroxyindole acetic acid and 5-hydroxytryptophol were found in the ovotestis. Catecholamines such as L-dopa, dopamine and homovanillic acid were identified in the albumen gland. Functional aspects of both dopamine and serotonin were studied using in vitro cultures of albumen glands, the site of perivitelline fluid and galactogen synthesis in B. glabrata. Dopamine was found to stimulate the release of secretory proteins when exogenously added to gland cultures and this process was inhibited by chlorpromazine, a dopamine receptor antagonist. Similarly, exogenous serotonin stimulated in vitro protein secretion by albumen glands. Thus, these results suggest that monoamines may play important roles in regulating reproductive activity of this snail and provides an excellent model for studying neurotransmitter function and metabolism in molluscs.
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Affiliation(s)
- V Santhanagopalan
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, 2115 Observatory Drive-Biotron, Madison, WI 53706, USA.
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49
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Lauder JM, Liu J, Grayson DR. In utero exposure to serotonergic drugs alters neonatal expression of 5-HT(1A) receptor transcripts: a quantitative RT-PCR study. Int J Dev Neurosci 2000; 18:171-6. [PMID: 10715571 DOI: 10.1016/s0736-5748(99)00085-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In embryonic rat brain, serotonin (5-HT) acts as a differentiation signal for 5-HT neurons and their target cells during midgestation. Serotonin receptors expressed during this period include the 5-HT(1A) subtype, which may mediate some of these developmental effects. Using the highly sensitive method of competitive RT-PCR, we quantified the effects of maternal treatment with either p-chlorophenylalanine (pCPA; which depletes 5-HT in embryonic rat brain) or 5-methoxytryptamine (5-MT; a general 5-HT(1) /5-HT(2) agonist) from embryonic day E12-17 on expression of 5-HT(1A) receptor mRNA transcripts in brains of offspring at postnatal day 4 (PND 4). In offspring of both pCPA and 5-MT treated mothers, 5-HT(1A) transcripts were significantly reduced compared to vehicle controls, although effects of pCPA were greater than those of 5-MT. These results indicate that either under-stimulation of 5-HT(1A) receptors (due to pCPA-induced 5-HT depletion) or over-stimulation (by the agonist 5-MT) during prenatal development significantly reduced expression of 5-HT(1A) receptor transcripts in neonatal offspring. This may occur by disruption of 5-HT(1A) gene transcription or by post-transcriptional mechanisms (such as altered translation or turnover of mRNA). Whatever the mechanism, reductions in 5-HT(1A) receptor transcripts following in utero exposure to serotonergic drugs could significantly impact the number of 5-HT(1A) receptors expressed in neonatal rat brain. Whether such effects will persist into adulthood remains to be determined.
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Affiliation(s)
- J M Lauder
- Department of Cell Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7090, USA
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50
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Darmani NA, Ahmad B. Early postnatal cocaine exposure causes sequential, dose-dependent, enduring but reversible supersensitivity in 5-HT2A receptor-mediated function during development in male mice. Neurotoxicol Teratol 2000; 22:61-9. [PMID: 10642115 DOI: 10.1016/s0892-0362(99)00054-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This report investigated whether postnatal exposure to cocaine affects the index of 5-HT2A receptor function during development by utilizing the ability of the 5-HT2A/C agonist DOI to induce the head-twitch response (HTR) in mice. Thus, several groups of mice litters were treated with varying doses of cocaine (0, 0.5, 1, 5, and 10 mg/kg, IP) twice daily from postnatal days 5 to 14. Then, different groups of cocaine-exposed male mice pups along with their corresponding age-matched vehicle-exposed control groups were HTR tested once during development on the following postnatal test days: 15, 16, 18, 20, 30, 45, and 60. The HTR testing involved administration of DOI (0.5 mg/kg, IP) and counting the frequency of the behavior for the next 20 min. Cocaine exposure caused bell-shaped, dose-dependent, enduring but reversible increase in DOI-induced HTR frequency (mean +/- SEM) during development. The developing pups were most sensitive to low and intermediate doses of cocaine (0.5-5 mg/kg). The greatest degree of increase in HTR frequency in response to DOI challenge occurred in the 1 mg/kg cocaine-exposure group on most test days. The onset of HTR supersensitivity varied from 48 h (5 mg/kg) to 144 h (0.5 mg/kg) following the termination of chronic cocaine exposure. Moreover, maximal supersensitivity for the latter doses of cocaine occurred 96 and 384 h postcocaine treatment, respectively. Other cocaine exposure groups attained their maxima sometime between the latter time periods. The duration of persistence of 5-HT2A receptor supersensitivity varied with different doses of cocaine: the 10-mg/kg group was supersensitive up to 384 h postcocaine treatment, the 1- and 5-mg/kg groups up to 744 h; and the 0.5-mg/kg group up to 1104 h. Although developmentally cocaine-exposed pups exhibit some similarities (i.e., exquisite sensitivity and bell-shaped dose-response) in 5-HT2A receptor adaptation to mature adult mice exposed to cocaine, they also differ from mature adult cocaine-exposed mice in the onset of appearance as well as the enduring persistence of the induced supersensitivity.
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Affiliation(s)
- N A Darmani
- Department of Pharmacology, Kirksville College of Osteopathic Medicine, MO 63501, USA.
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