Human social buffer in goats and dogs

The primary goal of this study was to explore the social buffering effect that humans offer to goats and dogs with limited exposure to human socialization, particularly in situations involving interactions with unfamiliar humans. A total of 13 dogs and 14 goats were selected for the study, all of which had limited prior socialization with humans. Each animal was placed in a testing room with unfamiliar humans for 15 min. Three experimenters aimed to establish a comfortable environment, encouraging social interaction by offering food to the animals and assessing the animals' willingness to accept food and their response to being approached and petted. If both conditions were satisfied, the animals were classified as "social". If one or none of the conditions were met, the animals were classified as "not social". Cortisol levels were measured by collecting blood samples before and after the test. Non-parametric tests together with a GzLM showed that the effect of human social buffering in goats was different in comparison to dogs: goats exhibited higher cortisol levels after the test, while dogs did not show a significant change. Further analysis demonstrated that "social" goats had a lower likelihood of experiencing significant changes in cortisol levels than dogs. Thus, once human interactions are accepted, both species could benefit from social buffering. In summary, this study enhances our understanding of how dogs and goats respond to social interactions with humans in the social buffering effect.

When are puppies receptive to emotion-induced human chemosignals? The cases of fear and happiness

We report an observational, double-blind, experimental study that examines the effects of human emotional odors on puppies between 3 and 6 months and adult dogs (one year and upwards). Both groups were exposed to control, human fear, and happiness odors in a between subjects' design. The duration of all behaviors directed to the apparatus, the door, the owner, a stranger, and stress behaviors was recorded. A discriminant analysis showed that the fear odor activates consistent behavior patterns for both puppies and adult dogs. However, no behavioral differences between the control and happiness odor conditions were found in the case of puppies. In contrast, adult dogs reveal distinctive patterns for all three odor conditions. We argue that responses to human fear chemosignals systematically influence the behaviors displayed by puppies and adult dogs, which could be genetically prefigured. In contrast, the effects of happiness odors constitute cues that require learning during early socialization processes, which yield consistent patterns only in adulthood.

The differential role of Leydig cells in the skin and gills of Lissotriton italicus larvae

Larval urodeles are provided with external gills involved, along with the skin, in gas exchange and osmoregulation. Gills and skin epithelia are different, each showing a peculiar set of specialized cells but both provided with Leydig cells (LCs). Information on LCs in the gills is lacking as the literature has focused primarily on the epidermis. Contradictory and fragmentary results highlight that LCs origin, fate, and functions remain not fully understood. Here, we investigated the morpho-functional differences of LCs in the skin and gills of Lissotriton italicus larvae for the first time. LCs showed the same morphological and ultrastructural features in both tissues, even if LCs were significantly larger in the epidermis. Despite the uniform morphology within the LCs population, the proliferative ability was different. The putative diversity in the mucus composition was evaluated using a panel of 4 lectins as markers of specific carbohydrate moieties, revealing that sites of specific glycoconjugates were comparable in two tissues. To disclose the involvement of LCs in water storage and transport, immunofluorescence assay for aquaporin-3 has also been performed, demonstrating the expression of this protein only in gills epithelium. By demonstrating that LCs can multiply by cell division in gills, our results will also contribute to the discussion about their proliferative ability. Finally, we found that the LCs cytoplasm is rich in glycoconjugates, which are involved in many diverse and essential functions in vertebrates.

Effects of ecotrofin™ on milk yield, milk quality and serum biochemistry in lactating goats

A nutritional supplement (Ecotrofin™, by Vetoquinol Italia S.r.l) recommended in ruminants feeding to strengthen the physiological condition and improve digestive performance was tested in 20 pluriparae grazing goats divided in two groups (control and treated) to assess its possible effects on milk yield and quality and to assess eventual adverse effects. Animals from both groups also received 400 g/day of corn meal, and the treated group was supplemented with 20 g/head/day of the nutritional supplement. At the doses suggested by the manufacturer, despite a transient increase after 30 days of supplementation, Ecotrofin™ did not show significant effects on milk yield and, although some changes were found in the fatty acids profile, no significant improvement of MUFA and PUFA, as well as of omega‐6:omega‐3 ratio and CLA content were seen. Therefore, in our experimental conditions the supplementation of diet with Ecotrofin™ did not appear useful to improve goat's performance. A significant effect on kidney health markers (27 vs. 22.5 for urea and 0.83 vs. 0.76 for creatinine, p < 0.05) suggested a beneficial effect on renal function but, since levels fell in the normal ranges in both groups, such hypothesis would need further studies to be addressed.

The scent of emotions: A systematic review of human intra- and interspecific chemical communication of emotions

OBJECTIVE

The sense of olfaction has been considered of minor importance in human communication. In recent years, evidence has emerged that humans might be influenced by unconscious messages sent through chemosignals in body odors. Data concerning the ability of humans to recognize fear, maybe related to the evolutionary role of these emotions in the fight-or-flight reactions, are well known.

METHODS

To further understand the role of emotional chemosignals in mediating communication in humans and its influence on animal behaviors, we conducted a systematic literature review.

RESULTS

Chemosignals derived from axillary odors collected under a variety of emotional stimuli and sad tears in humans affect receivers' social interactions, danger detection and risk-taking behavior, social aspects of eating, and performance under stressing conditions. In addition, beyond the fight-or-flight response, even the body odors of happiness can be perceived by others. Furthermore, human chemosignals can influence behaviors and stressful responses in animals, particularly dogs and horses, which may partially explain their special relationship with humans.

CONCLUSION

Our review highlights the importance of chemosignaling in human intra- and interspecific interactions and suggests the need for further investigations, both in physiological conditions and in patients with psychiatric or neurodegenerative disorders.

Development of a Spatial Discount Task to Measure Impulsive Choices in Dogs

Simple Summary

Impulsivity is believed to play a role in problematic behaviors in dogs. In this study, we developed a test to assess dogs’ tendency to make impulsive choices, that is their preference for smaller immediate reward instead of larger, but harder to obtain ones. Dogs were first trained that a bowl presented on a certain side always contained a large food amount, whereas the one presented on the opposite side (although at the same distance from the dog) contained less food. Then, the bowl with less food was progressively placed closer to the dog. As expected, dogs’ choices to feed from the bowl with less food increased as the distance of the latter decreased. Choices did not depend on factors that could interfere, such as dogs’ level of motivation for food, training experience, or learning ability. This indicates that the test is likely to be actually assessing impulsivity, not other traits. Also, female dogs were more likely to make impulsive choices than males, in accordance with what is known in humans and rodents, supporting the validity of the test. The test was completed in less than 1 h, making it a valid option to assess impulsivity in dogs in various contexts.

Abstract

Impulsive choices reflect an individual’s tendency to prefer a smaller immediate reward over a larger delayed one. Here, we have developed a behavioural test which can be easily applied to assess impulsive choices in dogs. Dogs were trained to associate one of two equidistant locations with a larger food amount when a smaller amount was presented in the other location, then the smaller amount was placed systematically closer to the dog. Choices of the smaller amount, as a function of distance, were considered a measure of the dog’s tendency to make impulsive choices. All dogs (N = 48) passed the learning phase and completed the entire assessment in under 1 h. Choice of the smaller food amount increased as this was placed closer to the dog. Choices were independent from food motivation, past training, and speed of learning the training phase; supporting the specificity of the procedure. Females showed a higher probability of making impulsive choices, in agreement with analogue sex differences found in human and rodent studies, and supporting the external validity of our assessment. Overall, the findings support the practical applicability and represent a first indication of the validity of this method, making it suitable for investigations into impulsivity in dogs.

Effects of a Nutritional Supplement on Cognitive Function in Aged Dogs and on Synaptic Function of Primary Cultured Neurons

Simple Summary

We tested the effects of a nutraceutical product, DiSenior^TM, by spatial navigation test and by in vitro and in vivo experiments. Results showed that DiSenior^TM was safe and able to ameliorate cognitive functions in aged dogs, as demonstrated by the better performances in the treated with respect the untreated groups. The increase of cFOS, a functional marker of activity in cultured neurons, indicated a positive effect of the substance on neuronal functions. The study suggests that DiSenior^TM can improve the quality of life of elderly dogs and may slow the onset of cognitive dysfunction symptoms associated with aging.

Abstract

The objective of this research was to investigate the efficacy of DìSenior^TM, a nutraceutical formulated to improve cognitive functions in elderly dogs. To this purpose, some clinical and metabolic investigations and a spatial navigation test were performed in treated and untreated dogs. Moreover, the nutraceutical was also tested on primary hippocampal neuron cultures. Results showed no adverse effects on the dogs’ health and a positive effect on learning. In vitro effects on neuron cultures showed an increase in the level of cFOS in treated neurons compared with the vehicle, suggesting that DiSenior^TM has also a positive effect on neuronal functions. Overall, this study suggests that DiSenior^TM can exert a beneficial effect on aged dogs by preventing the negative effects of aging on cognition. Further studies are needed to assess the mechanisms by which it acts on neurons and the specific effect of the different components alone or combined.

Training improves inhibitory control in water rescue dogs

Inhibitory control is a collection of several processes that are aimed to refrain from any impulsive response in the subject during inappropriate situations. Evidence suggests that in dogs, the inhibitory control is affected by domestication process, but also experiences during ontogeny could be an important driver in acquiring inhibitory control. The aim of the study was to compare the performance of highly trained dogs (i.e., water rescue dogs) and pet dogs in the A-not-B task. In this procedure, the animals have to inhibit their urge of going to a previous reinforced place. The results showed that the trained dogs committed fewer errors in the task than the pet dogs suggesting a better inhibitory control. This result could indicate that inhibitory control is a flexible ability affected by ontogenetic processes such as the training experience.

Fishing for Targets of Alien Metabolites: A Novel Peroxisome Proliferator-Activated Receptor (PPAR) Agonist from a Marine Pest

Although the chemical warfare between invasive and native species has become a central problem in invasion biology, the molecular mechanisms by which bioactive metabolites from invasive pests influence local communities remain poorly characterized. This study demonstrates that the alkaloid caulerpin (CAU)-a bioactive component of the green alga Caulerpa cylindracea that has invaded the entire Mediterranean basin-is an agonist of peroxisome proliferator-activated receptors (PPARs). Our interdisciplinary study started with the in silico prediction of the ligand-protein interaction, which was then validated by in vivo, ex vivo and in vitro assays. On the basis of these results, we candidate CAU as a causal factor of the metabolic and behavioural disorders observed in Diplodus sargus, a native edible fish of high ecological and commercial relevance, feeding on C. cylindracea. Moreover, given the considerable interest in PPAR activators for the treatment of relevant human diseases, our findings are also discussed in terms of a possible nutraceutical/pharmacological valorisation of the invasive algal biomasses, supporting an innovative strategy for conserving biodiversity as an alternative to unrealistic campaigns for the eradication of invasive pests.

¹H NMR Spectroscopy and MVA to Evaluate the Effects of Caulerpin-Based Diet on Diplodus sargus Lipid Profiles

The biological invasion of the green algae Caulerpa cylindracea represents a serious scientific and public issue in the Mediterranean Sea, essentially due to strong modifications both to habitat structure and native benthic communities. Although alterations in health status and changes in flesh quality of some marine species (dietary exposed to C. cylindracea) have been observed, no studies on cause-effect relationships have been carried out. Here, for the first time, through a controlled feeding experiment followed by ¹H NMR Spectroscopy and multivariate analysis (PCA, OPLS-DA), we showed that caulerpin taken with diet is directly responsible of changes observed in metabolic profile of fish flesh, including alteration of lipid metabolism, in particular with a reduction of ω3 PUFA content. The potential of caulerpin to directly modulate lipid metabolism opens up new questions about causal mechanism triggered by algal metabolite also in view of a possible exploitation in the nutraceutical/medical field.

Behavioral and Perceptual Differences between Sexes in Dogs: An Overview

In this paper, we review the scientific reports of sex-related differences in dogs as compared to the outcomes described for wild animals. Our aim was to explore whether the differences in male and female dogs were affected by the domestication process, in which artificial selection is the main driver. For this purpose, we used information regarding personality traits, cognitive processes, and perception, for which there is a wide theoretical framework in behavioral ecology. Aggressiveness and boldness, described as a behavioral syndrome, were reported as being higher in males than females. Females also seemed more inclined to interspecific social interactions with humans in tasks that require cooperative skills, whereas males appeared more inclined to social play, thus implying different levels of social engagement between the sexes, depending on the context. Studies on cognitive processes underlined a greater flexibility in resorting to a particular navigation strategy in males. Most lateralization studies seem to support the view that males are preferentially left-handed and females are preferentially right-handed. Reports on visual focusing coherently rank females as superior in focusing on single social and physical stimuli. Only male dogs are able to discriminate kin; however, the timing of the olfactory recording in sexes is related to the stimulus relevance. Dogs are largely in line with life-history theories, which indicate that sex differences in dogs are mainly rooted in their biological and evolutionary heritage, remaining unchanged despite artificial selection. In contrast, the higher intraspecific sociability in wild male animals was not replicated in dogs.

Should I fetch one or the other? A study on dogs on the object choice in the bimodal contrasting paradigm

The present study assessed how dogs weigh gestural versus verbal information communicated to them by humans in transitive actions. The dogs were trained by their owners to fetch an object under three conditions: a bimodal congruent condition characterized by using gestures and voices simultaneously; a unimodal gestural condition characterized by using only gestures; and a unimodal verbal condition characterized by using only voices. An additional condition, defined as a bimodal incongruent condition, was later added, in which the gesture contrasted with the verbal command, that is, the owner indicated an object while pronouncing the name of the other object visible to dogs. In the incongruent condition, seven out of nine dogs choose to follow the gestural indication and performed above chance, two were at chance, whereas none of the dogs followed the verbal cues above chance. The dogs, as a group, performed above chance the gestural command in 73.6% of cases. The analysis of latencies in the above-mentioned four conditions exhibited significant differences. The unimodal verbal and the gestural conditions recorded a slower performance than both the bimodal incongruent and congruent conditions. No statistical differences were observed between the unimodal and bimodal conditions. Our results demonstrate that dogs, trained to respond equally well to gestural and verbal commands, choose to follow the indication provided by the gestural command than the verbal one to a significant extent in transitive actions. Furthermore, the responses to bimodal conditions were found to be quicker than the unimodal ones.

d-Aspartic acid ameliorates painful and neuropsychiatric changes and reduces β-amyloid Aβ1-42 peptide in a long lasting model of neuropathic pain

Depressive symptoms and other neuropsychiatric dysfunctions are common in neurodegenerative disorders, including chronic pain and dementia. A correlation between the β-amyloid protein accumulation and the development of depression has been suggested, however the underlying mechanisms are unknown. d-Aspartate (d-Asp) is a free d-amino acid found in the mammalian brain and involved in neurological and psychiatric processes, such as cognition and affective disorders. In this study we have investigated the effects of a repeated treatment with d-Asp in a long-lasting (12 months) model of neuropathic pain, the spared nerve injury (SNI), in mice. Specifically, we evaluated i) the pain sensitivity and related emotional/cognitive dysfunctions induced by SNI, ii) possible changes in the β-amyloid protein accumulation in specific brain regions involved in pain mechanisms ii) possible changes in steroids level in neuropathic animals with or without d-Asp in the same brain areas. SNI mice showed an increase of the insoluble form of Aβ_1-42 at hippocampal level and displayed cognitive impairments, stereotypical and depressive-like behaviours. d-Asp treatment reduced abnormal behaviours and normalized the β-amyloid protein expression. Moreover, d-Asp dramatically increased steroids level measured in the prefrontal cortex and in the hippocampus. Our findings provide new insights into pain mechanisms and suggest a possible role of β-amyloid protein in neuropsychiatric dysfunctions associated with chronic pain.

Gonadotropin-inhibitory hormone (GnIH) in the amphibian brain and its relationship with the gonadotropin releasing hormone (GnRH) system: An overview

It is well known that the hypothalamic neuropeptide gonadotropin-releasing hormone (GnRH) plays an important role as a primary factor regulating gonadotropin secretion in reproductive processes in vertebrates. The discovery of the presence of a gonadotropin-inhibitory hormone (GnIH) in the brains of birds has further contributed to our understanding of the reproduction control by the brain. GnIH plays a key role in inhibition of reproduction and acts on the pituitary gland and GnRH neurons via a novel G protein-coupled receptor (GPR147). GnIH decreases gonadotropin synthesis and release, thus inhibiting gonadal development and maintenance. The GnRH and GnIH neuronal peptidergic systems are well reported in mammals and birds, but limited information is available regarding their presence and localization in the brains of other vertebrate species, such as reptiles, amphibians and fishes. The aim of this review is to compile and update information on the localization of GnRH and GnIH neuronal systems, with a particular focus on amphibians, summarizing the neuroanatomical distribution of GnIH and GnRH and emphasizing the discovery of GnIH based on RFamide peptides and GnIH orthologous peptides found in other vertebrates and their functional significance.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project

The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

The importance of gestural communication: a study of human-dog communication using incongruent information

We assessed how water rescue dogs, which were equally accustomed to respond to gestural and verbal requests, weighted gestural versus verbal information when asked by their owner to perform an action. Dogs were asked to perform four different actions ("sit", "lie down", "stay", "come") providing them with a single source of information (in Phase 1, gestural, and in Phase 2, verbal) or with incongruent information (in Phase 3, gestural and verbal commands referred to two different actions). In Phases 1 and 2, we recorded the frequency of correct responses as 0 or 1, whereas in Phase 3, we computed a 'preference index' (percentage of gestural commands followed over the total commands responded). Results showed that dogs followed gestures significantly better than words when these two types of information were used separately. Females were more likely to respond to gestural than verbal commands and males responded to verbal commands significantly better than females. In the incongruent condition, when gestures and words simultaneously indicated two different actions, the dogs overall preferred to execute the action required by the gesture rather than that required verbally, except when the verbal command "come" was paired with the gestural command "stay" with the owner moving away from the dog. Our data suggest that in dogs accustomed to respond to both gestural and verbal requests, gestures are more salient than words. However, dogs' responses appeared to be dependent also on the contextual situation: dogs' motivation to maintain proximity with an owner who was moving away could have led them to make the more 'convenient' choices between the two incongruent instructions.

Proliferative events and apoptotic remodelling in retinal development of common toad (Bufo bufo)

Proliferation and apoptosis are fundamental processes in the development of the retina, and a proper balance of the two phenomena is crucial to correct development of the organ. Despite intense investigation in different vertebrates, only a few studies have analyzed the cell death and the cell division quantitatively in the same species during development. Here we studied the time course of apoptosis and proliferation in the retina of common toad, Bufo bufo, and discuss the findings in an evolutionary perspective. We found cells that were dividing first scattered throughout the retina, then, in later stages, proliferation was confined to the ciliary marginal zone. This pattern was confirmed by the expression of the proliferative marker PCNA. Both proliferation and apoptosis occurred in successive waves, and two apoptotic peaks were detected: one at premetamorphosis 1 and the second at prometamorphosis. PARP-1, a known molecular marker of apoptosis, was used to confirm the data obtained by counting pyknotic nuclei. In summary, proliferative and apoptotic waves display an inverse time-relationship through development, with apoptotic peaks coinciding with low proliferation phases. In a comparative perspective, amphibians follow a developmental pattern similar to other vertebrates, although with different timing.

Guide dogs as a model for investigating the effect of life experience and training on gazing behaviour

The present study aimed at evaluating possible behavioural differences between guide dogs living in a kennel and interacting with a trainer and those living in a house and interacting with a blind person and their family, when they are faced with an unsolvable task. Fifty-two Labrador retrievers were tested: 13 Trained Guide dogs at the end of their training programme and 11 Working Guide dogs that had been living with their blind owner for at least 1 year. Two control groups of Labrador retrievers were also tested: 14 Young Untrained dogs of the same age as the Trained Guide and 14 Old Untrained dogs of the same age as the Working Guide dogs. Results showed that the Trained Guide dogs gazed towards the owner or the stranger for less time and with a higher latency and spent more time interacting with the experimental apparatus than the other three groups, which all behaved similarly. None of the groups tested showed preferences in gazing towards the stranger or the owner. Together, the results suggest that at the end of their training programme, guide dogs are less prone to engage in human-directed gazing behaviour and more likely to act independently when facing an unsolvable task. Conversely, guide dogs that have been living with a blind person (and their family) for 1 year behave like pet dogs. These findings indicate that guide dogs' gazing towards humans is favoured by living in close proximity with people and by interacting with them.

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – http://www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.

Gazing toward humans: a study on water rescue dogs using the impossible task paradigm

Various studies have assessed the role of life experiences, including learning opportunities, living conditions and the quality of dog-human relationships, in the use of human cues and problem-solving ability. The current study investigates how and to what extent training affects the behaviour of dogs and the communication of dogs with humans by comparing dogs trained for a water rescue service and untrained pet dogs in the impossible task paradigm. Twenty-three certified water rescue dogs (the water rescue group) and 17 dogs with no training experience (the untrained group) were tested using a modified version of the impossible task described by Marshall-Pescini et al. in 2009. The results demonstrated that the water rescue dogs directed their first gaze significantly more often towards the owner and spent more time gazing toward two people compared to the untrained pet dogs. There was no difference between the dogs of the two groups as far as in the amount of time spent gazing at the owner or the stranger; neither in the interaction with the apparatus attempting to obtain food. The specific training regime, aimed at promoting cooperation during the performance of water rescue, could account for the longer gazing behaviour shown toward people by the water rescue dogs and the priority of gazing toward the owner.

A comparative cluster analysis of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry in the brains of amphibians

Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) is a key enzyme in the synthesis of the gaseous neurotransmitter nitric oxide. We compare the distribution of NADPH-d in the brain of four species of hylid frogs. NADPH-d-positive fibers are present throughout much of the brain, whereas stained cell groups are distributed in well-defined regions. Whereas most brain areas consistently show positive neurons in all species, in some areas species-specific differences occur. We analyzed our data and those available for other amphibian species to build a matrix on NADPH-d brain distribution for a multivariate analysis. Brain dissimilarities were quantified by using the Jaccard index in a hierarchical clustering procedure. The whole brain dendrogram was compared with that of its main subdivisions by applying the Fowlkes-Mallows index for dendrogram similarity, followed by bootstrap replications and a permutation test. Despite the differences in the distribution map of the NADPH-d system among species, cluster analysis of data from the whole brain and hindbrain faithfully reflected the evolutionary history (framework) of amphibians. Dendrograms from the secondary prosencephalon, diencephalon, mesencephalon, and isthmus showed some deviation from the main scheme. Thus, the present analysis supports the major evolutionary stability of the hindbrain. We provide evidence that the NADPH-d system in main brain subdivisions should be cautiously approached for comparative purposes because specific adaptations of a single species could occur and may affect the NADPH-d distribution pattern in a brain subdivision. The minor differences in staining pattern of particular subdivisions apparently do not affect the general patterns of staining across species.

Proliferative activity in the frog brain: a PCNA-immunohistochemistry analysis

By means proliferating cell nuclear antigen (PCNA) immunohistochemistry, we have provided a detailed neuroanatomical mapping of proliferative activity during development and adulthood in the frog (Rana esculenta) brain. Western blot analysis confirmed the presence of this protein in brain extracts from adults and tadpoles. Proliferative activity was observed in the ventricular and subventricular zones throughout the brain. The present study provides details as to which of the morphologically distinguishable brain region(s) has a long-lasting proliferative activity and in which region this activity undergoes a progressive decrease during development. In the subventricular zones of the third ventricle, PCNA-labeled cells were particularly abundant in the magnocellular preoptic nucleus and the ventromedial thalamic nucleus. It was observed that proliferation zones are present practically in all major subdivisions of the forebrain, midbrain and hindbrain, including the cerebellum in which PCNA-labeled cells were located in the outer granular layer and the inner molecular layer. The habenulae, epiphysis and isthmic nuclei never showed the presence of PCNA-immunoreactive nuclei. The widespread proliferative activity implies that the frog brain has a great potential for neurogenesis/gliogenesis not only during larval development but also in the adulthood.

D-aspartic acid in the nervous system of Aplysia limacina: possible role in neurotransmission

In the marine mollusk Aplysia limacina, a substantial amount of endogenous D-aspartic acid (D-Asp) was found following its synthesis from L-aspartate by an aspartate racemase. Concentrations of D-Asp between 3.9 and 4.6 micromol/g tissue were found in the cerebral, abdominal, buccal, pleural, and pedal ganglia. In non nervous tissues, D-Asp occurred at a very low concentration compared to the nervous system. Immunohistochemical studies conducted on cultured Aplysia neurons using an anti-D-aspartate antibody demonstrated that D-Asp occurs in the soma, dendrites, and in synaptic varicosities. Synaptosomes and synaptic vesicles from cerebral ganglia were prepared and characterized by electron microscopy. HPLC analysis revealed high concentrations of D-Asp together with L-aspartate and L-glutamate in isolated synaptosomes In addition, D-Asp was released from synaptosomes by K+ depolarization or by ionomycin. D-Asp was one of the principal amino acids present in synaptic vesicles representing about the 25% of total amino acids present in these cellular organelles. Injection of D-Asp into live animals or addition to the incubation media of cultured neurons, caused an increase in cAMP content. Taken as a whole, these findings suggest a possible role of D-Asp in neurotransmission in the nervous system of Aplysia limacina.

Extrabulbar olfactory system and nervus terminalis FMRFamide immunoreactive components in Xenopus laevis ontogenesis

The extrabulbar olfactory system (EBOS) is a collection of nerve fibers which originate from primary olfactory receptor-like neurons and penetrate into the brain bypassing the olfactory bulbs. Our description is based upon the application of two neuronal tracers (biocytin, carbocyanine DiI) in the olfactory sac, at the cut end of the olfactory nerve and in the telencephalon of the developing clawed frog. The extrabulbar olfactory system was observed already at stage 45, which is the first developmental stage compatible with our techniques; at this stage, the extrabulbar olfactory system fibers terminated diffusely in the preoptic area. A little later in development, i.e. at stage 50, the extrabulbar olfactory system was maximally developed, extending as far caudally as the rhombencephalon. In the metamorphosing specimens, the extrabulbar olfactory system appeared reduced in extension; caudally, the fiber terminals did not extend beyond the diencephalon. While a substantial overlapping of biocytin/FMRFamide immunoreactivity was observed along the olfactory pathways as well as in the telencephalon, FMRFamide immunoreactivity was never observed to be colocalized in the same cellular or fiber components visualized by tracer molecules. The question whether the extrabulbar olfactory system and the nervus terminalis (NT) are separate anatomical entities or represent an integrated system is discussed.

Ontogenetic organization of the FMRFamide immunoreactivity in the nervus terminalis of the lungfish, Neoceratodus forsteri

The development of the nervus terminalis system in the lungfish, Neoceratodus forsteri, was investigated by using FMRFamide as a marker. FMRFamide immunoreactivity appears first within the brain, in the dorsal hypothalamus at a stage around hatching. At a slightly later stage, immunoreactivity appears in the olfactory mucosa. These immunoreactive cells move outside the olfactory organ to form the ganglion of the nervus terminalis. Immunoreactive processes emerge from the ganglion of the nervus terminalis in two directions, one which joins the olfactory nerve to travel to the brain and the other which courses below the brain to enter at the level of the preoptic nucleus. Neither the ganglion of the nervus terminalis nor the two branches of the nervus terminalis form after surgical removal of the olfactory placode at a stage before the development of FMRFamide immunoreactivity external to the brain. Because this study has confirmed that the nervus terminalis in lungfish comprises both an anterior and a posterior branch, it forms the basis for discussion of homology between these branches and the nervus terminalis of other anamniote vertebrates.

Localization of FMRFamide-like immunoreactivity in the brain of the viviparous skink (Chalcides chalcides)

Neuroanatomical distribution of FMRFamide-like immunoreactivity was investigated in the brain and olfactory system of the viviparous skink, Chalcides chalcides. In the adult brain FMRFamide immunoreactive (ir) perikarya were observed in the diagonal band of Broca, medial septal nucleus, accumbens nucleus, bed nucleus of the anterior commissure, periventricular hypothalamic nucleus, lateral forebrain bundle, and lateral preoptic, subcommissural, suprachiasmatic and lateral hypothalamic areas. This pattern was seen in both male and female brains. Though all major brain areas showed FMRFamide-ir innervation, the densest ir fiber network was observed in the hypothalamus. During development, ir elements were observed for the first time in embryos at mid-pregnancy. FMRFamide perikarya were located along the ventral surface of the vomeronasal nerve, in the olfactory peduncle mediobasally, as well as in the anterior olfactory nucleus and olfactory tubercle. Furthermore, some ir neurons were observed in the rhombencephalic reticular substance; however, the ir fiber network was poorly developed. Later in development FMRFamide-ir neurons appeared also in the bed nucleus of the anterior commissure as well as the rhombencephalic nucleus of solitary tract and the dorsal motor nucleus of vagus nerve. In juveniles, the distribution profile of FMRFamide immunoreactivity was substantially similar to that of the adults, with a less widespread neuronal distribution and a more developed fiber network. Ontogenetic presence of FMRFamide immunoreactivity in the nasal area has been linked to the presence of a nervus terminalis in this reptile.

FMRFamide in the amphibian brain: a comprehensive survey

Mapping of FMRFamidergic neural circuitry in the amphibian brain has been done by immunohistochemical methods. Comparative evidence suggests that there are similarities and differences in the overall pattern of distribution of FMRFamide-ir elements in the brain among the three amphibian orders and within each order. FMRFamide is expressed in neurons in some circumscribed areas of the brain. A part of these neurons is concentrated in classical neurosecretory areas of the hypothalamus in a bilaterally symmetrical fashion. Similar neurons occur occasionally in the midbrain, but are virtually absent from the hindbrain. Anurans are unique among amphibians to show FMRFamide neurons in the medial septum and diagonal band of Broca. A viviparous gymnophione is known to possess a small population of such neurons in the dorsal thalamus. Together, the FMRFamide neurons contribute to an extensive fiber network throughout the amphibian brain. Descriptive developmental studies suggest that the rostral forebrain-located FMRFamide neurons originate in the olfactory placode and then migrate into the brain along the route of the vomeronasal-olfactory-terminal nerve complex. Olfactory placodal ablation in an anuran and a urodele provide experimental support to this contention. Other FMRFamide neuronal cell groups, in the hypothalamus and dorsal thalamus, are supposed to arise from non-placodal precursors. The neuroanatomical distribution (projection of immunoreactive processes to areas of the fore-, mid-, and hindbrain as well as to cerebrospinal fluid, co-localization with other neuropeptides, and presence in the median eminence) has furnished morphological correlates of possible functions of FMRFamide in the amphibian CNS. While amphibian FMRFamide-like or structurally related peptides remain to be isolated and characterized, the sum of the distribution pattern of FMRFamide-like immunoreactivity suggests that it may act as a neurotransmitter or a neuromodulator, and also may have endocrine regulatory functions.

Development and distribution of FMRFamide-like immunoreactivity in the toad (Bufo bufo) brain

By using immunohistochemistry, we studied the development and distribution of the FMRFamide-like immunoreactive (ir) neuronal system in the toad brain during the ontogeny. In addition to this, experimental evidence was provided to show that the rostral forebrain-located FMRFamide neurons originate in the olfactory placode and then migrate into the brain along the olfactory pathway. During early development, within the brain, FMRFamide-ir perikarya first appeared in the periventricular hypothalamus. Later in development, FMRFamide-ir cells were visualized in the rostralmost forebrain simultaneously with similar ir cells in the developing olfactory mucosa. Selective ablation of the olfactory placode(s), prior to the appearance of the first FMRFamide-ir cells in the brain, resulted in the total absence of ir cells in the telencephalon (medial septum and mediobasal telencephalon) of the operated sides(s). The preoptic-suprachiasmatic-infundibular hypothalamus-located FMRFamide-ir neurons were not affected by olfactory placodectomy, arguing that they do not originate in the placode. This result points to the placode as the sole source of such neurons in the rostral forebrain.

Intrasexual and intersexual dimorphisms of the red salmon prosencephalon

Intrasexual as well as intersexual dimorphisms were found in the prosencephalon and mesencephalon of adult Oncorhynchus nerka (red/sockeye salmon). These dimorphisms are concerned with the position of the preoptic nucleus, nucleus lateralis tuberis, habenula, third ventricle, tectal ventricles, preoptic recess, recessus lateralis, horizontal commissure, posterior commissure, and toral commissure. The intrasexual dimorphism was characterized by either a rostral ("r"-pattern) or a caudal ("c"-pattern) position of the preoptic region as well as varying locations of other structures within the prosencephalon. As compared to "c"-pattern fish, the preoptic nucleus and nucleus lateralis tuberis were located more rostral, and the habenula was positioned further caudal, in "r"-type animals. The intersexual dimorphism was also characterized by different positions of the structures listed above. With the exception of the preoptic nucleus, all of these were located further rostral in "r"-pattern females than in type "r" males. In "c"-pattern females, they were positioned further caudal than in type "c" males. The number of neurons in the parvocellular and in the magnocellular portion of the preoptic region differed in the two genders with respect to "r"- as well as "c"-pattern fish. Males had more neurons than females in both the magno- and the parvocellular subdivisions of the preoptic region. In "r"- and "c"-pattern fish, the average size of magnocellular preoptic neurons was larger in females than in males. The observed intersexual variations may reflect gender-specific differences in the control of the pituitary. Functional correlates of intrasexual dimorphism are obscure.

Mammalian and chicken I forms of gonadotropin-releasing hormone in the gonads of a protochordate, Ciona intestinalis

Two forms of gonadotropin-releasing hormone (GnRH) were isolated from the gonads of the tunicate, Ciona intestinalis. The primary structure of the purified peptides was determined by MS and chemical sequence analysis. Both GnRH forms have blocked NH(2) and COOH termini, and their primary structures are identical to mammalian (mGnRH) and chicken I (cGnRH-I) forms reported previously in vertebrates. A total of 1.2 mg of purified cGnRH-I and 0.98 mg of mGnRH was obtained from 100 g of Ciona gonads. The physiological effects of native GnRHs included the induction of synthesis and secretion of sex steroids from ciona gonads and the secretion of luteinizing hormone from rat pituitary. These results suggest that the primary structure and functional roles of mGnRH and cGnRH-I have been highly conserved throughout evolution of chordates.

Comparative immunocytochemical study of FMRFamide neuronal system in the brain of Danio rerio and Acipenser ruthenus during development

The distribution of FMRFamide-like immunoreactive (ir) neurons and fibers was investigated in the central nervous system of developing zebrafish and juvenile sturgeon (sterlet). Adult zebrafish was also studied. In zebrafish embryos FMRFamide-ir elements first appeared 30 h post-fertilization (PF). Ir somata were located in the olfactory placode and in the ventral diencephalon. FMRFamide-ir fibers originating from diencephalic neurons were found in the ventral telencephalon and in ventral portions of the brainstem. At 48 h PF, the ir perikarya in the olfactory placode displayed increased immunoreactivity and stained fibers emerged from the somata. At 60 h PF, bilaterally, clusters of FMRFamide-ir neurons were found along the rostro-caudal axis of the brain, from the olfactory placode to rostral regions of the ventro-lateral telencephalon. At 60 h PF, numerous ir fibers appeared in the dorsal telencephalon, optic lobes, optic nerves, and retina. Except for ir fibers in the hypophysis at the age of 72 h PF, and a few ir cells in the nucleus olfacto-retinalis (NOR) at the age of 2 months PF, no major re-organization was noted in subsequent ontogenetic stages. The number of stained NOR neurons increased markedly in sexually mature zebrafish. In adult zebrafish, other ir neurons were located in the dorsal zones of the periventricular hypothalamus and in components of the nervus terminalis. We are inclined to believe that neurons expressing FMRFamide originate in the olfactory placode and in the ventricular ependyma in the hypothalamus. On the same grounds, a dual origin of FMRFamide-ir neurons is inferred in the sturgeon, an ancestral bony fish: prior to the observation of ir cells in the nasal area and in the telencephalon stained neurons were noted in circumventricular hypothalamic regions.

Comparative analysis of FMRFamide-like immunoreactivity in caiman (Caiman crocodilus) and turtle (Trachemys scripta elegans) brains

The distribution of FMRFamide (FMRFa)-like peptides in caiman (Caiman crocodilus) and turtle (Trachemys scripta elegans) brains was studied by immunohistochemistry. In both species, distinct groups of FMRFa-like immunoreactive (ir) perikarya were present in the medial septal nucleus, accumbens nucleus, nucleus of the diagonal band of Broca, suprachiasmatic area, lateral hypothalamic area, and periventricular hypothalamic nucleus. A few FMRFa-ir neurons in the hypothalamic area were located in the neuroepithelial cell lining of the third ventricle. FMRFa-ir fibers were scattered in all major areas of the brain, from the olfactory bulbs to the rhombencephalon. They formed dense aggregates in the medial septal area, basal telencephalon, median eminence, and infundibulum, and adjacent to the fourth ventricle. The most obvious difference between the FMRFa-ir systems in caimans and turtles concerned the number of nuclei that contained neurons with this immunoreactivity. Eight such clusters were present in the caiman brain, whereas thirteen clusters were found in the turtle brain. The turtle also displayed scattered FMRFa-ir somata in the anterior olfactory nucleus, striatum, lateral septal nucleus, medial and lateral cortex, medial forebrain bundle, lateral preoptic area, and lateral geniculate nucleus. In the caiman brain, a few FMRFa-ir neurons were noted in the ventrolateral area of the pallial commissure and an even smaller number of ir neurons was found dispersed in the optic tracts. Neither formed nuclear aggregates. The results are compared with those described for other vertebrates.

Distribution of FMRFamide-like immunoreactivity in the amphibian brain: comparative analysis

FMRFamide is a small neuropeptide present in particular neurons of the basal forebrain and midbrain of the vertebrate groups studied, especially fishes and mammals. In order to assess interspecies variation, the distribution of FMRFamide-like immunoreactivity was studied in the brains of 13 species of amphibian. Although FMRFamide-immunoreactive (IR) terminals occurred throughout much of the brain, IR cell groups were noted in circumscribed regions of the CNS. In the eight anuran species studied, two major populations of labeled perikarya were observed: one in the septopreoptic area and another one in the caudal portion of the diencephalon. The rostrocaudal extent of both and the number of labeled somata in each neuronal group displayed species-specific differences. In urodeles and gymnophiones, labeled perikarya were located in the diencephalon, but there were remarkable species differences in the number of such cells. It is discussed whether sex or season of collection may account for some of the differences observed. The distribution of FMRFamide-IR perikarya, fibers, and pathways in the brain of anurans, urodeles, and gymnophiones was compared. The existence of FMRFamide perikarya in the anterior preoptic neuropil and medial septum appeared to be a feature common to all anurans; labeled neurons in the dorsal thalamus, however, may be present only in the (viviparous) gymnophione Typhlonectes compressicauda. Cerebrospinal fluid contacting FMRFamide neuronal cell bodies and fibers were observed in each of the three taxonomic orders. The data are compared with those previously obtained for other groups of vertebrates.

Ontogenetic profile of FSH and LH in Rana esculenta

Circulating levels and pituitary content of FSH and LH were determined by specific radioimmunoassays in Rana esculenta starting a few days after hatching until the completion of metamorphosis. Both gonadotropins were found in the pituitary as well as in the blood plasma at all stages of development examined here. The plasma concentrations of FSH and LH were more or less uniform during pre- and prometamorphosis, but increased significantly at the onset of metamorphic climax. The plasma levels of FSH and LH remained high at the completion of metamorphosis. The pituitary content of FSH and LH was low in early premetamorphosis. It increased slightly through prometamorphosis and metamorphic climax, following which a highly significant increase occurred. Whereas plasma concentrations of FSH and LH were essentially similar within a single stage of development, the pituitary FSH content was severalfold higher than pituitary LH. The significance of these results is discussed in relation to the functional maturation of the brain-pituitary-gonadal axis in the frog.

Distribution of somatostatin-like immunoreactivity in the brain of the frog, Rana esculenta, during development

The anatomical distribution of somatostatin-like immunoreactivity in the central nervous system of the frog, Rana esculenta, during development and in juvenile specimens was investigated by indirect immunofluorescence. Soon after hatching, at stages II-III, somatostatin-like immunoreactive structures were found in the preoptic-median eminence complex. In stage VI tadpoles, new groups of immunopositive perikarya and nerve fibers appeared in the diencephalon, within the ventral infundibular nucleus and in the ventral area of the thalamus, as well as in the medial pallium. In stages XII-XIV of development, immunopositive perikarya were also present in the dorsal infundibular nucleus of the hypothalamus and ventrolateral area of the thalamus. A small group of somatostatin-like immunoreactive neurons appeared in the posteroventral nucleus of the rhombencephalon. However, these neurons were not seen in later stages of development. Tadpoles in stages XVIII, XXI-XXII and in juveniles were characterized by a wider distribution of immunoreactive cell bodies and fibers in the pallium. New groups of immunoreactive neurons were found in the dorsal and lateral pallium. The presence of positive perikarya in the lateral pallium is a transient expression found only in these stages. The organization of the somatostatinergic system was most complex during the metamorphic climax, with the appearance of positive cell bodies in the posterocentralis area of the thalamus, and in juvenile animals with the presence of perikarya in the ventral part of the medial pallium and within the central grey rhombencephali. In contrast to the adult frog, somatostatin neurons were not observed in the mesencephalon of tadpoles and juveniles.

Distribution of gonadotropin-releasing hormone immunoreactivity in the brain of Ichthyophis beddomei (Amphibia: Gymnophiona)

From a comparative viewpoint, we have investigated the presence and neuroanatomical distribution of gonadotropin-releasing hormone (GnRH)-immunoreactive material in the brain of a gymnophione amphibian, Ichthyophis beddomei. Immunocytochemical analysis of the adult brain and terminal nerves in both sexes shows the presence of neurons and fibers containing mammalian GnRH (mGnRH)- and chicken GnRH-II (cGnRH-II)-like peptides. With respect to GnRH-immunoreactive material, there are two distinct neuronal systems in the brain: one containing mGnRH, which is located in the forebrain and terminal nerve, and the other containing cGnRH-II, which is restricted to the midbrain tegmentum. Basically, this distribution pattern parallels that of many species of anurans and a urodele. Whereas the presence of cGnRH-II-immunoreactive fibers in the dorsal pallium of L. beddomei is a feature in common with a urodele amphibian, the total absence of cGnRH-II-like material in the median eminence is unique to this species. It is suggested here that the distribution profile of GnRH-like material within the brain and terminal nerve of I. beddomei represents a primitive pattern.

Differential labelling of primary olfactory system subcomponents by SBA (lectin) and NADPH-d histochemistry in the frog Pipa

SBA and NADPH-d histochemistries allow identification of functionally distinct components of the amphibian primary olfactory system. In Pipa, a secondarily aquatic frog, combination of both methodologies, using alternate sets of histological sections, reveals that, apart from Jacobson's organ, this species has a "water-nose" and an "air-nose". The epithelia occupy separate chambers of the olfactory organ and give rise to olfactory nerve fiber bundles that are identified by the dual staining procedure.

Sex and reproductive status related brain content of mammalian and chicken-II GnRHs in Rana esculenta

Mammalian and chicken-II forms of gonadotropin-releasing hormone (mGnRH and cGnRH-II, respectively) have been measured simultaneously in the brain, pituitary, and peripheral terminal nerves (nasal area tissue) of adult males and females of a representative amphibian, Rana esculenta, during the annual reproductive cycle. Whereas in the male, brain concentrations of both GnRH forms showed significant reproductive status-related fluctuations, in the female brain only cGnRH-II content showed significant changes. The highest GnRH levels were recorded just prior to breeding in both sexes. In the pituitary both GnRHs were present in all seasons. In the peripheral terminal nerves, instead, only mGnRH was detected in all seasons confirming our previous immunohistochemical data. In both sexes furthermore, the brain and pituitary mGnRH levels were consistently much higher than those of cGnRH-II and there were no sex-related differences in the brain and pituitary content of GnRHs. Seasonal changes in brain GnRH levels may correlate with plasma sex steroid levels reinforcing the postulate that sex steroids affect GnRH neuronal systems.

Immunohistochemical demonstration of FSH and LH in the pituitary of the developing frog, Rana esculenta

The ontogenetic pattern of immunohistochemically detectable FSH beta and LH beta cells was investigated in the pars distalis of the pituitary of the frog, Rana esculenta. The appearance, distribution, and percentage of these cells were examined in tadpoles from soon after hatching to the end of metamorphosis and in juveniles. We used monoclonal antibodies against bullfrog FSH beta and LH beta for single staining, and either mouse anti-bullfrog LH beta + guinea pig anti-rat FSH beta or rabbit polyclonal anti-bullfrog LH beta + mouse monoclonal anti-bullfrog FSH beta for double staining. The first appearance of gonadotropes, immunopositive for FSH beta, was revealed in stage 26 tadpoles. In successive stages of development the percentage of FSH beta-positive cells increased progressively and significantly. The mean percentage of these in the pars distalis cells increased from 0.7% in stage 26 to nearly 10% during the metamorphic climax (stages 31-33). In juveniles, the mean percentage of FSH beta-positive cells increased more than twofold compared to the climax value. The appearance of LH beta-positive cells was first recorded during the climax, and the mean percentage of LH beta-positive cells in juveniles reached levels as high as 30% or more, exceeding the number of FSH beta-positive cells. In climax, all LH beta-positive cells stained with anti-FSH beta as well. In juveniles, however, up to 80% of gonadotropes demonstrated colocalization of FSH beta and LH beta staining. We argue that both gonadotropins may be synthesized in all gonadotropes, and a small number of cells immunoreactive to either of the two gonadotropins may simply indicate that at that particular moment the cell contained detectable amounts of only one form of gonadotropin. These observations are discussed in relation to the possible involvement of hypothalamic influence in the differentiation of gonadotropes of the pituitary.

Distribution of FMRFamide-like immunoreactivity in the brain and pituitary of Rana esculenta during development

Developmental aspects of the distribution of FMRFamide (Phe-Met-Arg-Phe-NH2) immunoreactivity (ir) were investigated by indirect immunofluorescence in the brain, pituitary and terminal nerve of the frog, Rana esculenta. Soon after hatching. FMRFamide neurons were found in the proximal terminal nerve, mediobasal olfactory bulb, caudal dorsolateral pallium, diagonal band of Broca, anterior preoptic area, suprachiasmatic area, thalamus, infundibulum, and developing pituitary. FMRFamide fibers were present in the olfactory epithelium, terminal nerve, olfactory bulbs, dorsal and midventral telencephalon, epiphysis, mediolateral thalamus, pretectal gray, optic tectum, infundibulum, posterior interpeduncular nucleus-tegmentum area, and rostral rhombencephalon. During successive developmental stages, ir neurons were no longer observed in the dorsal telencephalon and pituitary. In late larval stages, ir neurons appeared in the medial septal area, and ir fibers in the cerebellum and torus semicircularis. At the same time, the frequency of ir neurons increased progressively in the anterior preoptic area, suprachiasmatic area and infundibulum. FMRFamide-ir neurons were never revealed in mesencephalon and rhombencephalon. Numerous ir fibers terminated in the median eminence and intermediate lobe of the pituitary. The adult pattern of distribution of FMRFamide-ir elements in the brain was achieved during the postmetamorphic development. In light of the existing literature, the possible placodal origin of forebrain-located FMRFamide neurons is briefly discussed.

Reproduction in the Mexican leaf frog, Pachymedusa dacnicolor. VI. Presence and distribution of multiple GnRH forms in the brain

The presence and distribution of gonadotropin-releasing hormone (GnRH) has been investigated in the Mexican leaf frog, Pachymedusa dacnicolor, brain during development and in the adult. The ontogenetic pattern of GnRH neurons illustrates their extracranial as well as intracranial sites. Immunohistochemical analysis indicates that GnRH-immunoreactive neurons appear during the metamorphic climax. They are located in the mesencephalon and subsequently other GnRH neurons appear in the peripheral terminal nerve and anterior preoptic area of the brain. Use of specific antisera and homologous combined with heterologous preabsorption tests indicate that mammalian and chicken GnRH-II-like peptide-containing neurons are differentially located within the brain, the former in the anterior preoptic area and peripheral terminal nerve and the latter in the mesencephalon. HPLC and RIA data suggest the presence of three forms of immunoreactive GnRH in the P. dacnicolor brain. A mammalian GnRH-like molecule and a chicken GnRH-II-like molecule are present. A third form, suspected to be [hydroxyproline9]mGnRH elutes before the mammalian GnRH.

Neuropeptide Y: localization in the brain and pituitary of the developing frog (Rana esculenta)

The immunohistochemical localization of neuropeptide Y (NPY)-like peptide has been investigated in the peripheral terminal nerve, brain and pituitary of the frog, Rana esculenta, during development. Soon after hatching, a rather simple NPY-immunoreactive (-ir) neuronal system is present, with elements located mainly in the diencephalon. When hind limbs appear and develop, the NPY-neuronal system undergoes considerable elaboration and NPY-ir perikarya appear in several regions of the telencephalon (dorsal, medial, and lateral pallium; medial septum; medioventral telencephalon; anterior preoptic area), diencephalon (ventromedial, central and posterior thalamic nuclei; suprachiasmatic nucleus; infundibulum), mesencephalon (anteroventral mesencephalic tegmentum), and rhombencephalon (central grey; area of the cerebellar and vestibular nuclei). The frequency of NPY-ir neurons increases during larval development, and then decreases in the anterior preoptic area during the metamorphic climax. Dense plexuses of NPY-ir fibers are formed in several brain areas. NPY-ir fibers are found in the peripheral terminal nerve, and ir-neurons through its course along the ventromedial surface of the olfactory bulbs. NPY-ir fiber projections to the median eminence and pars intermedia derive mainly from the ventral infundibular group of NPY-ir neurons, with a contribution from the suprachiasmatic group of NPY neurons. NPY and carboxyl terminal flanking peptide of proneuropeptide Y coexist in the same neurons throughout the brain. The ontogenetic pattern of NPY-ir neuronal system in the brain of Rana esculenta is remarkably different than that reported for Xenopus laevis.

Immunoreactive mammalian and chicken-II GnRHs in Rana esculenta brain during development

Two forms of gonadotropin-releasing hormone (mammalian, mGnRH and chicken-II, cGnRH-II) were measured by radioimmunoassay in the nasal area (containing peripheral terminal nerve), brain and pituitary of Rana esculenta during larval development, metamorphosis, and until prior to becoming reproductively active. Small amounts of both forms of GnRH were first detected in the brain extract of early tadpoles (stage 26-27, when hindlimbs begin to develop). Later, there was a gradual, but constant, stage-dependent increase in the brain content of GnRHs, with the most remarkable increase recorded at postclimax and in young frogs. In tadpoles, postclimax froglets, and young frogs, the brain concentration of mGnRH was higher than that of cGnRH-II, with a ratio of approximately 2:1 in favor of mGnRH. In juveniles, however, the brain extract contained more cGnRH-II than mGnRH. No GnRH immunoreactivity was detected in the nasal area until stage 31. In successive stages of development, however, only mGnRH was present in the nasal area, and this confirmed our previous immunohistochemical analysis which showed that the peripheral terminal nerve contains only mGnRH-immunoreactive neurons and fibers. Although both GnRH forms were detected in the anterior (telencephalon, diencephalon) and posterior (mesencephalon, rhombencephalon) brain halves from juveniles, mGnRH content predominated in the anterior half, whereas in the posterior half cGnRH-II was present in greater amounts. Pituitaries from male and female postclimax froglets and young frogs contained both forms of GnRH in a ratio of approximately 10:1 in favor of mGnRH. This finding may shed light on the question of which GnRH(s) regulate gonadotropin release from the pituitary. The developmental changes in GnRH-immunoreactive content of the brain and pituitary have been discussed in the light of functional maturation of the brain-pituitary-gonad axis.

Development and distribution of gonadotropin-releasing hormone neuronal systems in the frog (Rana esculenta) brain: immunohistochemical analysis

The ontogenesis of the gonadotropin-releasing hormone (GnRH) neuronal systems was studied in the brain of the frog, Rana esculenta. Attention was also focussed on the differential distribution of molecular forms of GnRH during development. The first GnRH-immunoreactive neurons appear in the mesencephalon of posterior limb-stage tadpoles. These neurons are shown to contain only chicken [His5,Trp7,Tyr8]GnRH (cGnRH-II). Later in development, mammalian [Tyr5,Leu7,Arg8] GnRH (mGnRH)-like peptide-containing neurons appear simultaneously in the terminal nerve as well as in the anterior preoptic area of the telencephalon. Subsequently, only after metamorphosis, mGnRH-containing neurons appear in the medial septal area of the posterior telencephalon. It is here shown that neurons containing the two forms of GnRH are distributed in distinct brain areas during development and in the adult: mGnRH-immunoreactive neurons in the terminal nerve, olfactory bulb, mediobasal telencephalon, medial septal area, anterior preoptic area, ventrolateral thalamus and infundibulum, whereas cGnRH-II neurons are located in the mesencephalon. We hypothesize that the terminal nerve/forebrain-located GnRH neurons express immunohistochemically late in development and originate extracranially migrating centrally, along the terminal nerve, during development, whereas those located in the mesencephalon express earlier and may have an intracranial site of origin.