Dynamic interactions of behavior and amine neurochemistry in acquisition and maintenance of social rank in crayfish

Simultaneous Dopamine and Serotonin Monitoring in Freely Moving Crayfish Using a Wireless Electrochemical Sensing System

Dopamine (DA) and serotonin (5-HT) are neurotransmitters that regulate a wide range of physiological and behavioral processes. Monitoring of both neurotransmitters with real-time analysis offers important insight into the mechanisms that shape animal behavior. However, bioelectronic tools to simultaneously monitor DA and 5-HT interactive dynamics in freely moving animals are underdeveloped. This is mainly due to the limited sensor sensitivity with miniaturized electronics. Here, we present a semi-implantable electrochemical device achieved by integrating a multi-surface-modified carbon fiber microelectrode with a miniaturized potentiostat module to detect DA and 5-HT in vivo with high sensitivity and selectivity. Specifically, carbon fiber microelectrodes were modified through electrochemical treatment and surface coatings to improve sensitivity, selectivity, and antifouling properties. A customized, lightweight potentiostat module was developed for untethered electrochemical measurements. Integrated with the microelectrode, the microsystem is compact (2.8 × 2.3 × 2.1 cm) to minimize its impacts on animal behavior and achieved simultaneous detection of DA and 5-HT with sensitivities of 48.4 and 133.0 nA/μM, respectively, within submicromolar ranges. The system was attached to the crayfish dorsal carapace, allowing electrode implantation into the heart of a crayfish to monitor DA and 5-HT dynamics, followed by drug injections. The semi-implantable biosensor system displayed a significant increase in oxidation peak currents after DA and 5-HT injections. The device successfully demonstrated the application for in vivo simultaneous monitoring of DA and 5-HT in the hemolymph (i.e., blood) of freely behaving crayfish underwater, yielding a valuable experimental tool to expand our understanding of the comodulation of DA and 5-HT.

Using crayfish behavior assay as a simple and sensitive model to evaluate potential adverse effects of water pollution: Emphasis on antidepressants

The freshwater crayfish, Procambarus clarkii is an excellent aquatic animal model that is highly adaptable and tolerant. P. clarkii is widely used as a toxicity model to study various pharmaceutical exposure. This animal model has complex behavioral traits and is considered sensitive to environmental changes, making it an excellent candidate to study psychoactive drugs based on a behavioral approach. However, up to now, most behavioral studies on crayfish use manual observation and scoring that require panelists. In this study, we aim to develop an automation pipeline to analyze crayfish behavior automatically. We use a deep-learning approach to label body parts in multiple crayfish, and based on the trajectory results, the intra- or inter-individual crayfish were calculated. Reliable and fast results of several behavior endpoints in multiple crayfish were retrieved. We then validated the detection performance of numerous crayfish in specific gender groups (male-male and female-female). Based on the result, the male crayfish displayed significantly higher aggression than females. We also tested the antidepressant exposure on this animal model to evaluate the psychoactive effects of this drug. As male crayfish display more distinct agonistic behavior than females, we exposed them to sertraline (SRT) 1 ppb for 7 and 14 days. It was revealed that sertraline was able to alter several behavioral endpoints in crayfish. Significant increases in extend claw ratio, total distance moved, average speed, and rapid movement were displayed in sertraline-exposed crayfish but decreased interaction time and longest interaction time. In addition, SRT 14 days exposure could atler the aggressiveness and bold behavior In the present method, DeepLabCut (DLC) has been utilized to analyze the locomotion behavior of multiple crayfish. This established method provides rapid and accurate ecotoxicity measurements using freshwater crayfish, which beneficient and applicable for environmental research.

Effects of Cymatocarpus solearis (Trematoda: Brachycoeliidae) on its second intermediate host, the Caribbean spiny lobster Panulirus argus

Many digenean trematodes require three hosts to complete their life cycle. For Cymatocarpus solearis (Brachycoeliidae), the first intermediate host is unknown; the Caribbean spiny lobster Panulirus argus is a second intermediate host, and the loggerhead turtle Caretta caretta, a lobster predator, is the definitive host. Trophically-transmitted parasites may alter the behavior or general condition of intermediate hosts in ways that increase the hosts' rates of consumption by definitive hosts. Here, we examined the effects of infection by C. solearis on P. argus by comparing several physiological and behavioral variables among uninfected lobsters (0 cysts) and lobsters with light (1-10 cysts), moderate (11-30 cysts), and heavy (>30 cysts) infections. Physiological variables were hepatosomatic index, growth rate, hemocyte count, concentration in hemolymph of cholesterol, protein, albumin, glucose, dopamine (DA) and serotonin (5-HT). Behavioral variables included seven components of the escape response (delay to escape, duration of swimming bout, distance traveled in a swimming bout, swim velocity, acceleration, force exerted, and work performed while swimming). There was no relationship between lobster size or sex and number of cysts. Significant differences among the four lobster groups occurred only in concentration of glucose (lower in heavily infected lobsters) and 5-HT (higher in heavily and moderately infected lobsters) in plasma. As changes in 5-HT concentration can modify the host's activity patterns or choice of microhabitat, our results suggest that infection with C. solearis may alter the behavior of spiny lobsters, potentially increasing the likelihood of trophic transmission of the parasite to the definitive host.

Identification and Characterization of 5-HT Receptor 1 from Scylla paramamosain: The Essential Roles of 5-HT and Its Receptor Gene during Aggressive Behavior in Crab Species

Biogenic amines (BAs) play an important role in the aggressive behavior of crustaceans. In mammals and birds, 5-HT and its receptor genes (5-HTRs) are characterized as essential regulators involved in neural signaling pathways during aggressive behavior. However, only one 5-HTR transcript has been reported in crabs. In this study, the full-length cDNA of the 5-HTR1 gene, named Sp5-HTR1, was first isolated from the muscle of the mud crab Scylla paramamosain using the reverse-transcription polymerase chain reaction (RT-PCR) and rapid-amplification of cDNA ends (RACE) methods. The transcript encoded a peptide of 587 amino acid residues with a molecular mass of 63.36 kDa. Western blot results indicate that the 5-HTR1 protein was expressed at the highest level in the thoracic ganglion. Furthermore, the results of quantitative real-time PCR show that the expression levels of Sp5-HTR1 in the ganglion at 0.5, 1, 2, and 4 h after 5-HT injection were significantly upregulated compared with the control group (p < 0.05). Meanwhile, the behavioral changes in 5-HT-injected crabs were analyzed with EthoVision. After 0.5 h of injection, the speed and movement distance of the crab, the duration of aggressive behavior, and the intensity of aggressiveness in the low-5-HT-concentration injection group were significantly higher than those in the saline-injection and control groups (p < 0.05). In this study, we found that the Sp5-HTR1 gene plays a role in the regulation of aggressive behavior by BAs, including 5-HT in the mud crab. The results provide reference data for the analysis of the genetic mechanism of aggressive behaviors in crabs.

Opposing effects of dopamine on agonistic behaviour in crayfish

The effects of dopamine on the agonistic behaviour of crayfish were analysed. When dopamine concentrations of 1 μmol l-1 were injected into large crayfish, individuals were beaten by smaller opponents, despite their physical advantage. Injection of 10 μmol l-1 dopamine into small animals increased their rate of winning against larger opponents. Injection of a D1 receptor antagonist prohibited the onset of a 'loser' effect in subordinate animals, suggesting that the inhibitory effect of dopamine on larger animals is mediated by D1 receptors. Similarly, injection of a D2 receptor antagonist prohibited the onset of a 'winner' effect in dominant animals, suggesting that the facilitating effect of dopamine on small animals is mediated by D2 receptors. Since the inhibitory effect of 1 μmol l-1 dopamine was similar to that seen with 1 μmol l-1 octopamine and the facilitating effect of 10 μmol l-1 dopamine was similar to that of 1 μmol l-1 serotonin, functional interactions among dopamine, octopamine and serotonin were analyzed by co-injection of amines with their receptor antagonists in various combinations. The inhibitory effect of 1 μmol l-1 dopamine disappeared when administered with D1 receptor antagonist, but remained when combined with octopamine receptor antagonist. Octopamine effects disappeared when administered with either D1 receptor antagonist or octopamine receptor antagonist, suggesting that the dopamine system is downstream of octopamine. The facilitating effect of 10 μmol l-1 dopamine disappeared when combined with serotonin 5HT1 receptor antagonist or D2 receptor antagonist. Serotonin effects also disappeared when combined with D2 receptor antagonist, suggesting that dopamine and serotonin activate each other through parallel pathways.

Evolution of stress responses refine mechanisms of social rank

Social rank functions to facilitate coping responses to socially stressful situations and conditions. The evolution of social status appears to be inseparably connected to the evolution of stress. Stress, aggression, reward, and decision-making neurocircuitries overlap and interact to produce status-linked relationships, which are common among both male and female populations. Behavioral consequences stemming from social status and rank relationships are molded by aggressive interactions, which are inherently stressful. It seems likely that the balance of regulatory elements in pro- and anti-stress neurocircuitries results in rapid but brief stress responses that are advantageous to social dominance. These systems further produce, in coordination with reward and aggression circuitries, rapid adaptive responding during opportunities that arise to acquire food, mates, perch sites, territorial space, shelter and other resources. Rapid acquisition of resources and aggressive postures produces dominant individuals, who temporarily have distinct fitness advantages. For these reasons also, change in social status can occur rapidly. Social subordination results in slower and more chronic neural and endocrine reactions, a suite of unique defensive behaviors, and an increased propensity for anxious and depressive behavior and affect. These two behavioral phenotypes are but distinct ends of a spectrum, however, they may give us insights into the troubling mechanisms underlying the myriad of stress-related disorders to which they appear to be evolutionarily linked.

Enhancement of synaptic responses in ascending interneurones following acquisition of social dominance in crayfish

When crayfish have attained dominant status after agonistic bouts, their avoidance reaction to mechanical stimulation of the tailfan changes from a dart to a turn response. Ascending interneurones originating in the terminal ganglion receive sensory inputs from the tailfan and they affect spike activity of both uropod and abdominal postural motor neurones, which coordinates the uropod and abdominal postural movements. Despite the varying output effects of ascending interneurones, the synaptic responses of all interneurones to sensory stimulation were enhanced when they acquired a dominant state. The number of spikes increased as did a sustained membrane depolarizations. Regardless of social status, the output effects on the uropod motor neurones of all interneurones except VE-1 remained unchanged. VE-1 mainly inhibited the uropod opener motor neurones in naive animals, but tended to excite them in dominant animals. Synaptic enhancement of the sensory response of ascending interneurones was also observed in naive animals treated with bath-applied serotonin. However, subordinate animals or naive animals treated with octopamine had no noticeable effect on the synaptic response of their ascending interneurones to sensory stimulation. Thus, enhancement of the synaptic response is a specific neural event that occurs when crayfish attain social dominance and it is mediated by serotonin.

Duality of 5-HT Effects on Crayfish Motoneurons

Serotonin (5-HT) is a major neuromodulator acting on the nervous system. Its various effects have been studied in vertebrates, as well as in arthropods, from the cellular and subcellular compartments up to the behavioral level, which includes the control of mood, aggression, locomotion, and anxiety. The diversity of responses of neurons to 5-HT has been related to its mode of application, the diversity of 5-HT-receptors, and the animals’ social status history. In the locomotor network of socially isolated crayfish, the duality of 5-HT-evoked responses (excitatory/inhibitory) on motoneurons (MNs), sensorimotor pathways, and their consequences on motor network activity has largely been studied. The aim of the present report is to examine if this duality of exogenous 5-HT-evoked responses in the crayfish locomotor network can be reproduced by direct activation of 5-HT neurons in the case of socially isolated animals. Our previous studies have focused on the mechanisms supporting these opposite effects on MNs, pointing out spatial segregation of 5-HT receptors responsible either for positive or negative responses. Here, we report new findings indicating that excitatory and inhibitory effects can be achieved simultaneously in different leg MNs by the activation of a single 5-HT cell in the first abdominal ganglion.

Three-dimensional organization of the brain and distribution of serotonin in the brain and ovary, and its effects on ovarian steroidogenesis in the giant freshwater prawn, Macrobrachium rosenbergii

The giant freshwater prawn, Macrobrachium rosenbergii, is an economically important crustacean species which has also been extensively used as a model in neuroscience research. The crustacean central nervous system is a highly complex structure, especially the brain. However, little information is available on the brain structure, especially the three-dimensional organization. In this study, we demonstrated the three-dimensional structure and histology of the brain of M. rosenbergii together with the distribution of serotonin (5-HT) in the brain and ovary as well as its effects on ovarian steroidogenesis. The brain of M. rosenbergii consists of three parts: protocerebrum, deutocerebrum and tritocerebrum. Histologically, protocerebrum comprises of neuronal clusters 6-8 and prominent anterior and posterior medial protocerebral neuropils (AMPN/PMPN). The protocerebrum is connected posteriorly to the deutocerebrum which consists of neuronal clusters 9-13, medial antenna I neuropil, a paired lateral antenna I neuropils and olfactory neuropils (ON). Tritocerebrum comprises of neuronal clusters 14-17 with prominent pairs of antenna II (AnN), tegumentary and columnar neuropils (CN). All neuronal clusters are paired structures except numbers 7, 13 and 17 which are single clusters located at the median zone. These neuronal clusters and neuropils are clearly shown in three-dimensional structure of the brain. 5-HT immunoreactivity (-ir) was mostly detected in the medium-sized neurons and neuronal fibers of clusters 6/7, 8, 9, 10 and 14/15 and in many neuropils of the brain including anterior/posterior medial protocerebral neuropils (AMPN/PMPN), protocerebral tract, protocerebral bridge, central body, olfactory neuropil (ON), antennal II neuropil (Ann) and columnar neuropil (CN). In the ovary, the 5-HT-ir was light in the oocyte step 1(Oc₁) and very intense in Oc₂-Oc₄. Using an in vitro assay of an explant of mature ovary, it was shown that 5-HT was able to enhance ovarian estradiol-17β (E₂) and progesterone (P₄) secretions. We suggest that 5-HT is specifically localized in specific brain areas and ovary of this prawn and it plays a pivotal role in ovarian maturation via the induction of female sex steroid secretions, in turn these steroids may enhance vitellogenesis resulting in oocyte growth and maturation.

Effects of sertraline on behavioral indices of crayfish Orconectes virilis

Sertraline, a selective serotonin re-uptake inhibitor, is a widely prescribed antidepressant in North America. Though sertraline is continuously released from wastewater treatment plant discharge to surface water, effects of aqueous exposure of sertraline on behavioral responses of aquatic animals are largely unknown. Our study explored the effects of aqueous exposures of sertraline on antagonistic bouts and predator response behavior of virile crayfish (Orconectes virilis). Crayfish were either exposed or not exposed to waterborne sertraline and then size-matched for paired antagonistic bouts to determine if sertraline affects the aggression of each crayfish. We investigated the effect of sertraline on responses to visual predator cues and determined whether sertraline acts as an olfactory cue. Our results demonstrate that crayfish exposed to sertraline are more aggressive when paired with control crayfish but, when sertraline crayfish are paired, there is no change in aggression. Attraction response to sertraline in behavioral mazes was also observed, which may represent a maladaptive behavior, and in an ecological context may result in crayfish moving to areas with elevated levels of sertraline. However, aqueous exposure to sertraline had no effect on predator responses of crayfish. Future research is warranted to determine whether such medicine released in wastewater treatment plant effluents produces long-term ecologically important consequences for aquatic animals residing in urbanized aquatic ecosystems.

Effects of Different Social and Environmental Conditions on Established Dominance Relationships in Crayfish

Like most social animals, crayfish readily form dominance relationships and linear social hierarchies when competing for limited resources. Competition often entails dyadic aggressive interactions, from which one animal emerges as the dominant and one as the subordinate. Once dominance relationships are formed, they typically remain stable for extended periods of time; thus, access to future resources is divided unequally among conspecifics. We previously showed that firmly established dominance relationships in juvenile crayfish can be disrupted by briefly adding a larger conspecific to the original pair. This finding suggested that the stability of social relationships in crayfish was highly context-dependent and more transient than previously assumed. We now report results that further identify the mechanisms underlying the destabilization of crayfish dominance relationships. We found that rank orders remained stable when conspecifics of smaller or equal size were added to the original pair, suggesting that both dominant and subordinate must be defeated by a larger crayfish in order to destabilize dominance relationships. We also found that dominance relationships remained stable when both members of the original pair were defeated by larger conspecifics in the absence of their original opponent. This showed that dominance relationships are not destabilized unless both animals experience defeat together. Lastly, we found that dominance relationships of pairs were successfully disrupted by larger intruders, although with reduced magnitude, after all chemical cues associated with earlier agonistic experiences were eliminated. These findings provide important new insights into the contextual features that regulate the stability of social dominance relationships in crayfish and probably in other species as well.

New evidence on an old question: is the "fight or flight" stage present in the cardiac and respiratory regulation of decapod crustaceans?

The ability to stay alert to subtle changes in the environment and to freeze, fight or flight in the presence of predators requires integrating sensory information as well as triggering motor output to target tissues, both of which are associated with the autonomic nervous system. These reactions, which are commonly related to vertebrates, are the fundamental physiological responses that allow an animal to survive danger. The circulatory activity in vertebrates changes in opposite phases. The stage where circulatory activity is high is termed the "fight or flight stage", while the stage where circulatory activity slows down is termed the "rest and digest stage". It may be assumed that highly evolved invertebrates possess a comparable response system as they also require rapid cardiovascular and respiratory regulation to be primed when necessary. However, in invertebrates, the body plan may have developed such a system very differently. Since this topic is insufficiently studied, it is necessary to extend studies for a comparative analysis. In the present review, we use our own experimental results obtained in the crab Neohelice granulata and both older and newer findings obtained by other authors in decapod crustaceans as well as in other invertebrates, to compare the pattern of change in circulatory activity, especially in the "fight or flight" stage. We conclude that the main features of neuroautonomic regulation of the cardiac function were already present early in evolution, at least in highly evolved invertebrates, although conspicuous differences are also evident.

Identification and developmental expression of the enzymes responsible for dopamine, histamine, octopamine and serotonin biosynthesis in the copepod crustacean Calanus finmarchicus

Neurochemicals are likely to play key roles in physiological/behavioral control in the copepod crustacean Calanus finmarchicus, the biomass dominant zooplankton for much of the North Atlantic Ocean. Previously, a de novo assembled transcriptome consisting of 206,041 unique sequences was used to characterize the peptidergic signaling systems of Calanus. Here, this assembly was mined for transcripts encoding enzymes involved in amine biosynthesis. Using known Drosophila melanogaster proteins as templates, transcripts encoding putative Calanus homologs of tryptophan-phenylalanine hydroxylase (dopamine, octopamine and serotonin biosynthesis), tyrosine hydroxylase (dopamine biosynthesis), DOPA decarboxylase (dopamine and serotonin biosynthesis), histidine decarboxylase (histamine biosynthesis), tyrosine decarboxylase (octopamine biosynthesis), tyramine β-hydroxylase (octopamine biosynthesis) and tryptophan hydroxylase (serotonin biosynthesis) were identified. Reverse BLAST and domain analyses show that the proteins deduced from these transcripts possess sequence homology to and the structural hallmarks of their respective enzyme families. Developmental profiling revealed a remarkably consistent pattern of expression for all transcripts, with the highest levels of expression typically seen in the early nauplius and early copepodite. These expression patterns suggest roles for amines during development, particularly in the metamorphic transitions from embryo to nauplius and from nauplius to copepodite. Taken collectively, the data presented here lay a strong foundation for future gene-based studies of aminergic signaling in this and other copepod species, in particular assessment of the roles they may play in developmental control.

Aminergic control of social status in crayfish agonistic encounters

Using pairings of male crayfish Procambarus clarkii with a 3–7% difference in size, we confirmed that physically larger crayfish were more likely to win encounters (winning probability of over 80%). Despite a physical disadvantage, small winners of the first pairings were more likely to win their subsequent conflicts with larger naive animals (winning probability was about 70%). By contrast, the losers of the first pairings rarely won their subsequent conflicts with smaller naive animals (winning probability of 6%). These winner and loser effects were mimicked by injection of serotonin and octopamine. Serotonin-injected naive small crayfish were more likely to win in pairings with untreated larger naive crayfish (winning probability of over 60%), while octopamine-injected naive large animals were beaten by untreated smaller naive animals (winning probability of 20%). Furthermore, the winner effects of dominant crayfish were cancelled by the injection of mianserin, an antagonist of serotonin receptors and were reinforced by the injection of fluoxetin, serotonin reuptake inhibitor, just after the establishment of social order of the first pairings. Injection of octopamine channel blockers, phentolamine and epinastine, by contrast, cancelled the loser effects. These results strongly suggested that serotonin and octopamine were responsible for winner and loser effects, respectively.

Spatial segregation of excitatory and inhibitory effects of 5-HT on crayfish motoneurons

Altering neuronal membrane properties, including input resistance, is a key modulatory mechanism for changing neural activity patterns. The effect of membrane currents generated by either synaptic or voltage-dependent channels directly depends on neuron input resistance. We found that local application of serotonin to different regions of identified motoneurons (MNs) of the postural/walking network of isolated crayfish produced different changes in input resistance. Puff-applied 5-HT in the periphery of the initial segment produced exclusively inhibitory responses. In contrast, when 5-HT was puff-applied on the central arbor of the same depressor (Dep) MN, exclusively depolarizing responses were obtained. Both inhibitory and excitatory responses were direct because they persisted in low-calcium saline. We found numerous close appositions between 5-HT-immunoreactive processes and the initial segment of dextran-rhodamine-filled Dep MNs. In contrast, almost no close apposition sites were found in Dep MN arbor. It seems that the 5-HT controls the level of excitability of postural network MNs by two mechanisms acting at two different sites: inhibitory responses (consistent with an action involving opening of K(+) channels) occur in the initial segment region and may involve classic synaptic transmission, whereas depolarizing responses (consistent with an action involving closing of K(+) channels) occur on MN branches via apparent paracrine effects.

Serotonin, motivation, and playfulness in the juvenile rat

The effects of the selective 5HT(1A) agonist 8-OH-DPAT were assessed on the play behavior of juvenile rats. When both rats of the test pair were comparably motivated to play, the only significant effect of 8-OH-DPAT was for play to be reduced at higher doses. When there was a baseline asymmetry in playful solicitation due to a differential motivation to play and only one rat of the pair was treated, low doses of 8-OH-DPAT resulted in a collapse of asymmetry in playful solicitations. It did not matter whether the rat that was treated initially accounted for more nape contacts or fewer nape contacts, the net effect of 8-OH-DPAT in this model was for low doses of 8-OH-DPAT to decrease a pre-established asymmetry in play solicitation. It is concluded that selective stimulation of 5HT(1A) receptors changes the dynamic of a playful interaction between two participants that are differentially motivated to play. These results are discussed within a broader framework of serotonergic involvement in mammalian playfulness.

Crustacean neuroendocrine systems and their signaling agents

Decapod crustaceans have long served as important models for the study of neuroendocrine signaling. For example, the process of neurosecretion was first formally demonstrated by using a member of this order. In this review, the major decapod neuroendocrine organs are described, as are their phylogenetic conservation and neurochemistry. In addition, recent advances in crustacean neurohormone discovery and tissue mapping are discussed, as are several recent advances in our understanding of hormonal control in this group of animals.

A naturally occurring human minidysferlin protein repairs sarcolemmal lesions in a mouse model of dysferlinopathy

Dysferlinopathies are autosomal recessive, progressive muscle dystrophies caused by mutations in DYSF, leading to a loss or a severe reduction of dysferlin, a key protein in sarcolemmal repair. Currently, no etiological treatment is available for patients affected with dysferlinopathy. As for other muscular dystrophies, gene therapy approaches based on recombinant adeno-associated virus (rAAV) vectors are promising options. However, because dysferlin messenger RNA is far above the natural packaging size of rAAV, full-length dysferlin gene transfer would be problematic. In a patient presenting with a late-onset moderate dysferlinopathy, we identified a large homozygous deletion, leading to the production of a natural "minidysferlin" protein. Using rAAV-mediated gene transfer into muscle, we demonstrated targeting of the minidysferlin to the muscle membrane and efficient repair of sarcolemmal lesions in a mouse model of dysferlinopathy. Thus, as previously demonstrated in the case of dystrophin, a deletion mutant of the dysferlin gene is also functional, suggesting that dysferlin's structure is modular. This minidysferlin protein could be used as part of a therapeutic strategy for patients affected with dysferlinopathies.

Individual aggressiveness in the crab Chasmagnathus: Influence in fight outcome and modulation by serotonin and octopamine

In a previous work we found that size-matched Chasmagnathus crabs establish winner-loser relationships that were stable over successive encounters but no evidence of escalation was revealed through fights. Here, we evaluated the hypothesis that size-matched fights between these crabs would be resolved according to the contestants' level of aggressiveness. Moreover, we aim at analysing the proximate roots of aggression, addressing the influence of the biogenic amines serotonin (5HT) and octopamine (OA) in crab's agonistic behaviour. To achieve these purposes, the following experiments were carried out. First, we performed successive fight encounters between the same opponents, varying the number of encounters and the interval between them, to assess the stability and progression of the winner-loser relationship. Then, we analysed dominance relationships in groups of three crabs, evaluating the emergence of linearity. Thirdly, we examined the effects of 5HT and OA injections over the fight dynamics and its result. Our findings show that contest outcome is persistent even through four encounters separated by 24h, but a comparison between encounters does not reveal any saving in fight time or increase in the opponent disparity. Within a group of crabs, a rank-order of dominance is revealed which is reflected in their fight dynamics. Interestingly, these results would not be due to winner or loser effects, suggesting that fight outcome could be mainly explained as resulting from differences in the level of aggressiveness of each opponent. Moreover, this individual aggressiveness can be modulated in opposite directions by the biogenic amines 5HT and OA, being increased by 5HT and decreased by OA.

Exploring new compounds for functional imaging using a crayfish (Procambarus clarkia) aggression paradigm

Covalently bonding multiple fluorine atom tags to the precursors of monoamines could provide compounds for functional imaging. Theoretically, the fluorine atoms can produce detectible signal if concentrated in vesicles inside neurons. Prior to committing more costly resources to the project, evidence was sought for uptake of the molecules into neurons in living organisms. Two 19F tag configurations of seven or nine atoms were investigated. Crayfish aggression provided a paradigm for obtaining preliminary data on the scarce new molecules. After establishing that 5-hydroxytryptophan (5-HTP) elicited serotonin-like effects, the fluorine tagged versions (PF-5-HTP) were investigated; then, the elevated aggression produced by these precursors to serotonin was blocked by coadministering fluoxetine. Treatment order effects and interrater reliability of the behavioral inventory were evaluated. Preliminary evidence that these imaging compounds are taken up into neurons obtained by studying crayfish behavior later found support using more sophisticated neuroscience techniques.

Personality change during depression treatment: a placebo-controlled trial

CONTEXT

High neuroticism is a personality risk factor that reflects much of the genetic vulnerability to major depressive disorder (MDD), and low extraversion may increase risk as well. Both have been linked to the serotonin system.

OBJECTIVES

To test whether patients with MDD taking selective serotonin reuptake inhibitors (SSRIs) report greater changes in neuroticism and extraversion than patients receiving inert placebo, and to examine the state effect hypothesis that self-reported personality change during SSRI treatment is merely a change of depression-related measurement bias.

DESIGN

A placebo-controlled trial.

SETTING

Research clinics. Patients Adult patients with moderate to severe MDD randomized to receive paroxetine (n = 120), placebo (n = 60), or cognitive therapy (n = 60).

OUTCOME MEASURES

NEO Five-Factor Inventory and Hamilton Rating Scale for Depression.

RESULTS

Patients who took paroxetine reported greater personality change than placebo patients, even after controlling for depression improvement (neuroticism, P < .001; extraversion, P = .002). The advantage of paroxetine over placebo in antidepressant efficacy was no longer significant after controlling for change in neuroticism (P = .46) or extraversion (P = .14). Patients taking paroxetine reported 6.8 times as much change on neuroticism and 3.5 times as much change on extraversion as placebo patients matched for depression improvement. Although placebo patients exhibited substantial depression improvement (Hamilton Rating Scale for Depression score, -1.2 SD, P < .001), they reported little change on neuroticism (-0.18 SD, P = .08) or extraversion (0.08 SD, P = .50). Cognitive therapy produced greater personality change than placebo (P </= .01); but its advantage on neuroticism was no longer significant after controlling for depression (P = .14). Neuroticism reduction during treatment predicted lower relapse rates among paroxetine responders (P = .003) but not among cognitive therapy responders (P = .86).

CONCLUSIONS

Paroxetine appears to have a specific pharmacological effect on personality that is distinct from its effect on depression. If replicated, this pattern would disconfirm the state effect hypothesis and instead support the notion that SSRIs' effects on personality go beyond and perhaps contribute to their antidepressant effects.

The effects of the herbicide metolachlor on agonistic behavior in the crayfish, Orconectes rusticus

Previous research suggests that agricultural herbicides interfere with olfactory-mediated behavior, such as responses to alarm signals and the ability to locate food, in aquatic organisms. In crayfish, aggressive interactions are also mediated by chemical signals. These social signals are important in establishing dominance, which in turn has an impact on an individual's ability to find and use mates, food, and habitat space. In this study, we investigated the impact of exposure to sublethal levels of the herbicide metolachlor on the ability of crayfish to respond to olfactory signals used in agonistic behaviors. Crayfish were exposed to three different environmentally relevant concentrations (60 ppb, 70 ppb, and 80 ppb) of metolachlor for 96 hours. Each exposed crayfish was then placed in a fight arena and was allowed to interact with a naïve, untreated crayfish for 15 minutes. We analyzed several characteristics of fighting behavior, including initial aggressiveness, time to fight, intensity levels, duration, number of encounters, and the winner and loser of each fight. Crayfish exposed to 80 ppb metolachlor were less likely to initiate and win encounters against naïve conspecifics than any other treatment group. Analysis of fight dynamics shows that metolachlor does not alter the temporal fighting dynamics within crayfish aggression. We conclude that high sublethal concentrations of metolachlor may be interfering with the ability of crayfish to receive or respond to social signals and thus affect certain agonistic behaviors.

The muscle protein dysferlin accumulates in the Alzheimer brain

Dysferlin is a transmembrane protein that is highly expressed in muscle. Dysferlin mutations cause limb-girdle dystrophy type 2B, Miyoshi myopathy and distal anterior compartment myopathy. Dysferlin has also been described in neural tissue. We studied dysferlin distribution in the brains of patients with Alzheimer disease (AD) and controls. Twelve brains, staged using the Clinical Dementia Rating were examined: 9 AD cases (mean age: 85.9 years and mean disease duration: 8.9 years), and 3 age-matched controls (mean age: 87.5 years). Dysferlin is a cytoplasmic protein in the pyramidal neurons of normal and AD brains. In addition, there were dysferlin-positive dystrophic neurites within Aβ plaques in the AD brain, distinct from tau-positive neurites. Western blots of total brain protein (RIPA) and sequential extraction buffers (high salt, high salt/Triton X-100, SDS and formic acid) of increasing protein extraction strength were performed to examine solubility state. In RIPA fractions, dysferlin was seen as 230–272 kDa bands in normal and AD brains. In serial extractions, there was a shift of dysferlin from soluble phase in high salt/Triton X-100 to the more insoluble SDS fraction in AD. Dysferlin is a new protein described in the AD brain that accumulates in association with neuritic plaques. In muscle, dysferlin plays a role in the repair of muscle membrane damage. The accumulation of dysferlin in the AD brain may be related to the inability of neurons to repair damage due to Aβ deposits accumulating in the AD brain.

Effects of Emdogain on osteoblast gene expression

OBJECTIVE

Emdogain (EMD) is a protein extract purified from porcine enamel and has been introduced in clinical practice to obtain periodontal regeneration. EMD is composed mainly of amelogenins (90%), while the remaining 10% is composed of non-amelogenin enamel matrix proteins such as enamelins, tuftelin, amelin and ameloblastin. Enamel matrix proteins seem to be involved in root formation. EMD has been reported to promote proliferation, migration, adhesion and differentiation of cells associated with healing periodontal tissues in vivo.

DESIGN

How this protein acts on osteoblasts is poorly understood. We therefore attempted to address this question by using a microarray technique to identify genes that are differently regulated in osteoblasts exposed to enamel matrix proteins.

RESULTS

By using DNA microarrays containing 20,000 genes, we identified several upregulated and downregulated genes in the osteoblast-like cell line (MG-63) cultured with enamel matrix proteins (Emd). The differentially expressed genes cover a broad range of functional activities: (i) signaling transduction, (ii) transcription, (iii) translation, (iv) cell cycle regulation, proliferation and apoptosis, (v) immune system, (vi) vesicular transport and lysosome activity, and (vii) cytoskeleton, cell adhesion and extracellular matrix production.

CONCLUSIONS

The data reported are the first genome-wide scan of the effect of enamel matrix proteins on osteoblast-like cells. These results can contribute to our understanding of the molecular mechanisms of bone regeneration and as a model for comparing other materials with similar clinical effects.

Biogenic amine levels, reproduction and social dominance in the queenless ant Streblognathus peetersi

Social harmony often relies on ritualized dominance interactions between society members, particularly in queenless ant societies, where colony members do not have developmentally predetermined castes but have to fight for their status in the reproductive and work hierarchy. In this behavioural plasticity, their social organisation resembles more that of vertebrates than that of the "classic" social insects. The present study investigates the neurochemistry of the queenless ant species, Streblognathus peetersi, to better understand the neural basis of the high behavioural plasticity observed in queenless ants. We report measurements of brain biogenic amines [octopamine, dopamine, serotonin] of S. peetersi ants; they reveal a new set of biogenic amine influences on social organisation with no common features with other "primitively organised societies" (bumble bees) and some common features with "highly eusocial" species (honey bees). This similarity to honey bees may either confirm the heritage of queenless species from their probably highly eusocial ancestors or highlight independent patterns of biogenic amine influences on the social organisation of these highly derived species.

The Integration of Behaviour into Comparative Physiology

Comparative physiology has traditionally focused on the physiological responses of animals to their physicochemical environment. In recent years, awareness has increased among physiologists of the potential for behavioural factors, such as the social environment of the animal, to affect physiological condition and responses. This recognition has led to an emerging trend within the field toward using multidisciplinary approaches that incorporate both behavioural and physiological techniques. Research areas in which the integrated study of behaviour and physiology has been particularly fruitful include the physiology of the social environment, sensory physiology and behaviour, and physiological constraints on behavioural ecology. The manner in which incorporating behavioural considerations has informed the physiological data collected is discussed for each of these areas using specific examples.

Dysferlinopathy associated with rigid spine syndrome

Dysferlinopathy and rigid spine syndrome occurring in a 50-year-old man is reported. The patient noticed stiffness of knee and ankle joints, which gradually extended to neck, wrist and elbow joints leading to difficulty in anterior flexion. Muscular weakness and wasting of the lower extremities had developed since age 40, accompanied by a limitation of anterior bending of the spine. Elevated serum CK was noticed. Muscle CT revealed atrophy with moderate fatty replacement of muscles in the neck, shoulder and pelvic girdle, and marked replacement in the para-vertebral muscles, posterior compartment of hamstrings and calf muscles. Electromyography showed a typical myogenic pattern, and muscle biopsy disclosed dystrophic changes, compatible with limb-girdle muscular dystrophy 2B. Loss of dysferlin expression was verified by immunohistochemistry, which was confirmed by a mini-multiplex Western blotting system. Gene analyses of the dysferlin gene disclosed compound heterozygotes for frameshift (G3016 + 1A) and a missense mutation (G3370T). This study might propose some clues to resolve the combination of musular dystrophies and rigid spine syndrome.

Behavioral effects of serotonin and serotonin agonists in two crayfish species, Procambarus clarkii and Orconectes rusticus

Exogenous serotonin elicits several behaviors in Procambarus clarkii, including a flexed, elevated posture, reduced locomotion, and changes in aggressive behavior. We conducted experiments to determine if several serotonin agonists mimicked the behavioral effects of serotonin in two crayfish species, P. clarkii and Orconectes rusticus. Drugs tested were 1-(3-Chlorophenyl)-piperazine dihydrochloride (mCPP), Oxymetazoline, 2,5-dimethoxy-4-iodoamphetamine (DOI), CGS-12066A, and (+/-)-8-hydroxy-2-(di-n-dipropylamino) tetralin (8-OH-DPAT). In P. clarkii, mCPP most closely mimicked the effects of serotonin, significantly increasing the performance of the flexed, elevated posture and reducing locomotion; 8-OH-DPAT significantly reduced locomotion as well. Both of these drugs produced significant increases in elevated posture and decreases in locomotion in O. rusticus, and in this species, the drugs at test concentrations were more effective in eliciting these effects than serotonin. The effects of the drugs on behaviors performed during fighting bouts were variable. In both species, only 8-OH-DPAT significantly reduced several agonistic behaviors, and no agonist or 5-HT itself produced significant increases in agonistic behavior.

Dysferlin mutation analysis in a group of Italian patients with limb-girdle muscular dystrophy and Miyoshi myopathy

Mutations in the dysferlin gene (DYSF) on chromosome 2p13 cause distinct phenotypes of muscular dystrophy: limb-girdle muscular dystrophy type 2B (LGMD2B), Miyoshi myopathy (MM), and distal anterior compartment myopathy, which are known by the term 'dysferlinopathy'. We performed mutation analyses of DYSF in 14 Italian patients from 10 unrelated families with a deficiency of dysferlin protein below 20% of the value in normal controls by immunoblotting analysis. We identified 11 different mutations, including eight missense and three deletion mutations. Nine of them were novel mutations. We also identified a unique 6-bp insertion polymorphism within the coding region of DYSF in 15% of Italian population, which was not observed in East Asian populations. The correlation between clinical phenotype and the gene mutations was unclear, which suggested the role of additional genetic and epigenetic factors in modifying clinical symptoms.

Dynamics and mechanics of social rank reversal

Stable social relationships are rearranged over time as resources such as favored territorial positions change. We test the hypotheses that social rank relationships are relatively stable, and although social signals influence aggression and rank, they are not as important as memory of an opponent. In addition, we hypothesize that eyespots, aggression and corticosterone influence serotonin and N-methyl-D: -aspartate (NMDA) systems in limbic structures involved in learning and memory. In stable adult dominant-subordinate relationships in the lizard Anolis carolinensis, social rank can be reversed by pharmacological elevation of limbic serotonergic activity. Any pair of specific experiences: behaving aggressively, viewing aggression or perceiving sign stimuli indicative of dominant rank also elevate serotonergic activity. Differences in the extent of serotonergic activation may be a discriminating and consolidating factor in attaining superior rank. For instance, socially aggressive encounters lead to increases in plasma corticosterone that stimulate both serotonergic activity and expression of the NMDA receptor subunit 2B (NR(2B)) within the CA(3) region of the lizard hippocampus. Integration of these systems will regulate opponent recognition and memory, motivation to attack or retreat, and behavioral and physiological reactions to stressful social interactions. Contextually appropriate social responses provide a modifiable basis for coping with the flexibility of social relationships.

Venom effects on monoaminergic systems

The monoamines, dopamine, epinephrine, histamine, norepinephrine, octopamine, serotonin and tyramine serve many functions in animals. Many different venoms have evolved to manipulate monoaminergic systems via a variety of cellular mechanisms, for both offensive and defensive purposes. One common function of monoamines present in venoms is to produce pain. Some monoamines in venoms cause immobilizing hyperexcitation which precedes venom-induced paralysis or hypokinesia. A common function of venom components that affect monoaminergic systems is to facilitate distribution of other venom components by causing vasodilation at the site of injection or by increasing heart rate. Venoms of some scorpions, spiders, fish and jellyfish contain adrenergic agonists or cause massive release of catecholamines with serious effects on the cardiovascular system, including increased heart rate. Other venom components act as agonists, antagonists or modulators at monoaminergic receptors, or affect release, reuptake or synthesis of monoamines. Most arthropod venoms have insect targets, yet, little attention has been paid to possible effects of these venoms on monoaminergic systems in insects. Further research into this area may reveal novel effects of venom components on monoaminergic systems at the cellular, systems and behavioral levels.

Serotonin enhances the resistance reflex of the locomotor network of the crayfish through multiple modulatory effects that act cooperatively

Serotonin (5HT) is an endogenous amine that modifies posture in crustacea. Here, we examined the mechanisms of action of 5HT on the resistance reflex in crayfish legs. This reflex, which counteracts movements imposed on a limb, is based on a negative feedback system formed by proprioceptors that sense joint angle movements and activate opposing motoneurons. We performed intracellular recordings from depressor motoneurons while repetitively stretching and releasing a leg joint proprioceptor in a resting in vitro preparation (i.e., a preparation that lacks spontaneous rhythmic activity). 5HT increased the amplitude of the depolarization during the release phase of the proprioceptor (corresponding to an upward movement of the leg) and the discharge frequency of the motoneurons. The 5HT-induced increase in the resistance reflex is caused, to a large extent, by polysynaptic pathways because it was very attenuated in the presence of high divalent cation solution. In addition to this activation of the polysynaptic pathways, 5HT also has postsynaptic effects that enhance the resistance reflex. 5HT causes a tonic depolarization, as well as an increase in the time constant and input resistance of motoneurons. We developed a simple mathematical model to describe the integrative properties of the motoneurons. The conclusion of this study is that the input frequency and the decay time constant of the EPSPs interact in such a way that small simultaneous changes in these parameters can cause a large effect on summation. Therefore, the conjunction of presynaptic and postsynaptic changes produces a strong cooperative effect on the resistance reflex response.

Aggression in invertebrates

Invertebrates are outstanding model systems for the study of aggression. Recent advances and promising new research approaches are bringing investigators closer to the goal of integrating behavioral findings with those from other disciplines of the neurosciences. The presence of highly structured, easily evoked behavioral systems offer unique opportunities to quantify the aggressive state of individuals, to explore the mechanisms underlying the formation and maintenance of dominance relationships, to investigate the dynamic properties of hierarchy formation, and to explore the significance of neural, neurochemical and genetic mechanisms in these behavioral phenomena.

A crustacean serotonin receptor: Cloning and distribution in the thoracic ganglia of crayfish and freshwater prawn

Serotonin (5-HT) is involved in regulating important aspects of behavior and a variety of systemic physiological functions in both vertebrates and invertebrates. These functions are mediated through binding to 5-HT receptors, of which approximately 13 have been characterized in mammals. In crustaceans, important model systems for the study of the neural basis of behaviors, 5-HT is also linked with higher-order behaviors, associated with different 5-HT receptors that have been identified at the physiological and pharmacological levels. However, no crustacean 5-HT receptors have been identified at the molecular level. We have cloned a putative 5-HT(1) receptor (5-HT(1crust)) from crayfish, prawn, and spiny lobster and have raised antibodies that recognize this protein in all three organisms. 5-HT(1crust) immunoreactivity (5-HT(1crust)ir) was observed surrounding the somata of specific groups of neurons and as punctate staining within the neuropil in all thoracic ganglia of crayfish and prawn. In the crayfish, 5-HT(1crust)ir was also found in boutons surrounding the first and second nerves of each ganglion and on the 5-HT cells of T1-4. In the prawn, 5-HT(1crust)ir was also found in axons that project across the ganglia and along the connectives. We found examples of colocalization of 5-HT(1crust) with 5-HT, consistent with the short-term modulatory role of 5-HT, as well as cases of serotonergic staining in the absence of a 5-HT(1crust) signal, which might imply that other 5-HT receptors are found at these locations. We also observed receptors that did not possess counterpart 5-HT staining, suggesting that these may also mediate long-term neurohormonal functions of serotonin.

Male-like behavioral patterns and physiological alterations induced by androgenic gland implantation in female crayfish

The androgenic gland (AG) has been shown to regulate male sexual differentiation and secondary male characteristics in Crustacea. This study presents for the first time in crustaceans evidence for masculinization effects of the AG on reproductive behavior, in addition to morpho-anatomical and physiological effects. AG implantation into immature female red claw crayfish Cherax quadricarinatus inhibited secondary vitellogenesis and development of the ovaries, as well as morphological traits that facilitate maternal egg brooding; it also caused the appearance of secondary male characteristics. However, primary male characteristics and a masculine reproductive system were not developed. In pair encounters, aggression was substantially lower in interactions between AG-implanted and intact females than in interactions within AG-implanted or intact pairs. Moreover, elements of mating behavior, i.e. male courtship displays and false copulations, were exhibited by AG-implanted females in several encounters with intact females. In addition to known morpho-anatomical and physiological effects of the AG in crustaceans, the present study suggests that the AG has novel effects on the neural network that generates social behavior.

The neural basis of dominance hierarchy formation in crayfish

Fifty years of study of the nervous system and behavior of crayfish have revealed neural circuits for movements that are similar to those seen during formation of a dominance hierarchy. Given this background, it is of interest to ask what is understood about the neural substrates of dominance hierarchy formation. Here we will consider the social behavior that crayfish display in the wild and in the laboratory, and its relationship to movements released by activation of specific neural circuits. We will consider how these movements might be knit together to produce the behavior patterns that are characteristic of dominant and subordinate animals.

Amine neurochemistry and aggression in crayfish

A primary goal of our research is to explore proximate mechanisms important in recruiting adaptive social behaviors. For instance, if one of three different behaviors may be expressed in a particular set of circumstances, how do neurochemical mechanisms bias behavior towards the expression of one act in lieu of the other possibilities? In this article, we review recent results suggesting that serotonin may play such a role in the control of aggression in crayfish. First, we summarize techniques that have been optimized for sensitive characterization of neurochemical profiles in crayfish. Then, borrowing concepts from behavioral ecology, we review a framework for quantitative investigation, which regards behavior as a set of individual decisions, each with a particular probability for occurrence, a motivational context, and controlled by its own distinct neurochemical mechanisms.

Muscle pathology in dysferlin deficiency

Dysferlin deficiency is being increasingly recognized in limb-girdle dystrophy and distal myopathy but its role in the development of muscle pathology is still poorly understood. For this purpose, 26 muscle biopsies from 25 dysferlinopathy patients were analysed by routine histochemistry and by immunohistochemistry with eight different antibodies, and scored for inflammatory response and type of cell infiltrate, fibre degeneration and regeneration, fibre type composition and severity of histopathological changes. In cases with an advanced-stage dystrophic pattern we observed type 1 fibre predominance exceeding 80%, suggesting a selective loss of type 2 fibres or a conversion process. The extent of muscle fibre regeneration and degeneration in dysferlinopathy was intermediate between sarcoglycanopathy and Duchenne dystrophy or myositis, suggesting a rather aggressive course of the disease. An increased inflammatory response was observed in the majority of our patients (16/26), who also showed an active dystrophic pattern. Type and localization of cellular infiltrates suggest that inflammatory reaction is secondary to necrosis. Major histocompatibility complex (MHC) class I molecules were overexpressed in dysferlinopathy, mainly in association with fibre phagocytosis and regeneration; their occasional expression in non-necrotic fibres might represent a marker of ongoing necrosis. Muscle inflammation might be triggered by the structurally altered membrane consequent to dysferlin defect.

Chronic alterations in serotonin function: dynamic neurochemical properties in agonistic behavior of the crayfish, Orconectes rusticus

The biogenic amine serotonin [5-hydroxytryptamine (5-HT)] has received considerable attention for its role in behavioral phenomena throughout a broad range of invertebrate and vertebrate taxa. Acute 5-HT infusion decreases the likelihood of crayfish to retreat from dominant opponents. The present study reports the biochemical and behavioral effects resulting from chronic treatment with 5-HT-modifying compounds delivered for up to 5 weeks via silastic tube implants. High performance liquid chromatography with electrochemical detection (HPLC-ED) confirmed that 5,7-dihydroxytryptamine (5,7-DHT) effectively reduced 5-HT in all central nervous system (CNS) areas, except brain, while a concurrent accumulation of the compound was observed in all tissues analyzed. Unexpectedly, two different rates of chronic 5-HT treatment did not increase levels of the amine in the CNS. Behaviorally, 5,7-DHT treated crayfish exhibited no significant differences in measures of aggression. Although treatment with 5-HT did not elevate 5-HT content in the CNS, infusion at a slow rate caused animals to escalate more quickly while 5-HT treatment at a faster rate resulted in slower escalation. 5,7-DHT is commonly used in behavioral pharmacology and the present findings suggest its biochemical properties should be more thoroughly examined. Moreover, the apparent presence of powerful compensatory mechanisms indicates our need to adopt an increasingly dynamic view of the serotonergic bases of behavior like crayfish aggression.