Involvement of the avian song system in reproductive behaviour.

The song system of songbirds consists of an interconnected set of forebrain nuclei that has traditionally been regarded as dedicated to the learning and production of song. Here, however, we suggest that the song system could also influence muscles used in reproductive behaviour, such as the cloacal sphincter muscle. We show that the same medullary nucleus, retroambigualis (RAm), that projects upon spinal motoneurons innervating expiratory muscles (which provide the pressure head for vocalization) and upon vocal motoneurons for respiratory-vocal coordination also projects upon cloacal motoneurons. Furthermore, RAm neurons projecting to sacral spinal levels were shown to receive direct projections from nucleus robustus arcopallialis (RA) of the forebrain song system. Thus, by indicating a possible disynaptic relationship between RA and motoneurons innervating the reproductive organ, in both males and females, these results potentially extend the role of the song system to include consummatory as well as appetitive aspects of reproductive behaviour.

Distinct neuroendocrine mechanisms control neural activity underlying sex differences in sexual motivation and performance.

Sexual behavior can be usefully parsed into an appetitive and a consummatory component. Both appetitive and consummatory male-typical sexual behaviors (respectively, ASB and CSB) are activated in male Japanese quail by testosterone (T) acting in the medial preoptic nucleus (POM), but never observed in females. This sex difference is based on a demasculinization (= organizational effect) by estradiol during embryonic life for CSB, but a differential activation by T in adulthood for ASB. Males expressing rhythmic cloacal sphincter movements (RCSMs; a form of ASB) or allowed to copulate display increased Fos expression in POM. We investigated Fos brain responses in females exposed to behavioral tests after various endocrine treatments. T-treated females displayed RCSM, but never copulated when exposed to another female. Accordingly they showed an increased Fos expression in POM after ASB but not CSB tests. Females treated with the aromatase inhibitor Vorozole in ovo and T in adulthood displayed both male-typical ASB and CSB, and Fos expression in POM was increased after both types of tests. Thus, the neural circuit mediating ASB is present or can develop in both sexes, but is inactive in females unless they are exposed to exogenous T. In contrast, the neural mechanism mediating CSB is not normally present in females, but can be preserved by blocking the embryonic production of estrogens. Overall these data confirm the difference in endocrine controls and probably neural mechanisms supporting ASB and CSB in quail, and highlight the complexity of mechanisms underlying sexual differentiation of behavior.

The development of excitatory neurons in the chick cloaca.

INTRODUCTION: The enteric nervous system of the chick embryo hindgut is derived from the vagal and sacral neural tube. Nerve cells from these regions produce various neuronal phenotypes, including inhibitory and excitatory nerve cells, providing intrinsic innervation to the chick embryo cloaca. We hypothesised that the vagal and sacral neural tubes provide the cloaca, with phenotypically similar nerve cells. The aim of our study was to investigate the origin of excitatory neurotransmission in the developing cloaca. MATERIALS AND METHODS: Chicken embryos were incubated until the 10-12 somite stage (ss). To study the vagal neural tube contribution to the cloaca, this region was microsurgically ablated in ovo and replaced with the corresponding region from age-matched quail embryos. To study the sacral neural tube contribution to the cloaca, the vagal neural tube was ablated at the 10-12 ss, but not replaced with quail neural tube, thus, only the sacral neural crest cells remained. All embryos were harvested at E12 and E14, embedded in paraffin wax and serially sectioned. Immunohistochemistry was carried out on all embryos using human natural killer-1, quail non-chick perinuclear, choline acetyltransferase (ChAT) and substance P (SubP) antibodies. RESULTS: Choline acetyltransferase- and SubP-positive neurons were seen to originate in both the vagal and the sacral neural tube. The vagal neural tube provided the majority of the nerve cells to the chick embryo cloaca and expressed both ChAT and SubP in both the myenteric and submucosal plexus. The sacral neural tube contributed a lesser amount of nerve cells to the chick embryo cloaca, but was also seen to produce both ChAT- and SubP-positive nerve cells in both ganglionated plexus. CONCLUSION: This study shows, for the first time, that the excitatory ChAT- and SubP-expressing neurons in the developing cloaca originate in both the vagal and the sacral neural tube. These results highlight the origin of phenotypically similar nerve cells in both regions of the neural tube, providing new insights into the developmental origin of the intrinsic innervation of the persistent cloaca.

Cholinergic innervation in the developing chick cloaca and colorectum.

PURPOSE: Acetylcholine is the major excitatory neurotransmitter involved in intestinal contraction and therefore plays a pivotal role in normal gastrointestinal motility. Acetylcholinesterase (AchE) is an enzyme involved in hydrolysing acetylcholine during its metabolism. The AchE histochemistry can therefore be used to label acetylcholine-positive nerve cells and fibres, giving an overview of cholinergic innervation in the gut. Persistent cloaca is the most common anorectal malformation seen in female infants. The normal avian embryo contains a cloaca, reminiscent to the human malformation, which acts as a collecting chamber into which the digestive, urinary, and reproductive tracts merge. The aim of our study was to investigate cholinergic innervation in the chick embryo cloaca and colorectum at various stages of development. METHODS: Chick embryos were harvested at embryonic days 12 (E12), E14, E16, and E18. The colorectum and cloaca were removed from each embryo and frozen. Frozen transverse sections were then cut and AchE histochemistry was performed. The AchE staining was evaluated and graded using light microscopy. RESULTS: Results of our study show that acetylcholine is increasingly expressed in the chick embryo cloaca and colorectum from E12 to E18, with a stronger expression in the colorectum at each stage. The AchE-positive ganglia and fibres were evident in the submucosal and myenteric plexuses at all stages in both the cloaca and the colorectum. Ganglia size was seen to increase with age, and there was a notable increase in the amount of AchE-positive nerve fibres. CONCLUSION: Results show an increase in cholinergic innervation in both the cloaca and colorectum during development. As acetylcholine is the major excitatory neurotransmitter in the enteric nervous system, this study provides us with valuable information regarding the regional differences in the development of cholinergic innervation of the embryonic hindgut.

Vagal neural crest provides inhibitory neurotransmission to the chick embryo cloaca.

INTRODUCTION: The intrinsic innervation of the developing chick cloaca originates in the vagal and sacral regions of the neural tube. Its major inhibitory neurotransmitters are nitric oxide (NO) and vasoactive intestinal peptide (VIP). It has previously been shown that the majority of neurons in the chick embryo cloaca are derived from vagal neural crest cells. This study aimed to identify the phenotype of these vagal-derived neurons using quail-chick chimeras. MATERIALS AND METHODS: Chicken embryos were incubated until the 10-12 somite stage. The vagal neural tube was then microsurgically ablated in ovo and replaced with the vagal neural tube from age-matched quail embryos. Quail-chick chimera embryos were harvested at E12, and E14, and fixed and embedded in paraffin wax, and serially sectioned. Immunohistochemistry was performed using human natural killer-1 (HNK-1), quail-cell-specific perinuclear (QCPN), NOS and VIP antibodies. Expression of NOS and VIP neurons in the developing chick embryo cloaca was also further analysed using immunohistochemistry. RESULTS: HNK-1 labelled all ganglia in the myenteric and submucosal plexuses of the cloaca, whilst the quail-specific QCPN antibody labelled all ganglia derived from the transplanted quail vagal neural tube. NOS- and VIP-immunoreactive neurons appeared to make up a large proportion of the quail-derived vagal neural crest cells. Both NOS and VIP expression was seen to increase throughout development. CONCLUSION: This data suggests for the first time that the inhibitory neurons in the chick cloaca primarily originate in the vagal neural crest, thus providing new insights into the developmental origin of the intrinsic innervation of the developing cloaca.

RET/GDNF signalling in vagal neural crest-derived neurons of the chick embryo cloaca.

INTRODUCTION: The growth factor, 'Glial cell line-Derived Neurotrophic Factor' (GDNF), is involved in the development of enteric ganglia, using the tyrosine kinase receptor 'REarranged during Transfection' (RET) to stimulate the proliferation and differentiation of neural crest-derived precursor cells. To date, the presence of these signalling molecules have not been studied in the developing cloaca, thus the aim of this study was to investigate the distribution of RET and GDNF, and analyse their co-localisation in vagal-derived neurons of the cloaca using quail-chick chimera embryos. MATERIALS AND METHODS: Chicken embryos were incubated until the 10-12 somite stage. The vagal neural tube was microsurgically ablated in ovo and replaced with the vagal neural tube from age-matched quail embryos. Quail-chick chimera embryos were harvested at E12, fixed and embedded in paraffin wax, and serially sectioned. Immunohistochemistry was performed using human natural killer-1 (HNK-1), quail-cell-specific perinuclear (QCPN), GDNF and RET antibodies. RESULTS: HNK-1 labelled all ganglia in the myenteric and submucosal plexuses of the cloaca, while the quail-specific QCPN antibody labelled all ganglia derived from the transplanted quail vagal neural tube (Fig. 1, a, b). RET and GDNF were found both co-localised and expressed in separate ganglia in the cloaca (Fig. 1, c, d). The majority of QCPN-labelled vagal-derived neurons also expressed RET and GDNF. Fig. 1 HNK-1 (a), QCPN (b), GDNF (c) and RET (d) immunoreactivity in the chick cloaca at E12. Arrows show ganglia displaying co-immunoreactivity for all four antibodies CONCLUSION: Results show that GDNF and RET signalling play a major role in ENS development in the chick embryo cloaca. We have shown, for the first time, that the majority of vagal neural crest-derived neurons co-express RET and GDNF, thus highlighting the importance of these signalling factors in cloacal development.

Stichopin-containing nerves and secretory cells specific to connective tissues of the sea cucumber.

Stichopin, a 17-amino acid peptide isolated from a sea cucumber, affects the stiffness change of the body-wall catch connective tissues and the contraction of the body-wall muscles. The localization of stichopin in sea cucumbers was studied by indirect immunohistochemistry using antiserum against stichopin. Double staining was performed with both stichopin antiserum and 1E11, the monoclonal antibody specific to echinoderm nerves. A stichopin-like immunoreactivity (stichopin-LI) was exclusively found in the connective tissues of various organs. Many fibres and cells with processes were stained by both the anti-stichopin antibody and 1E11. They were found in the body-wall dermis and the connective tissue layer of the cloacae and were suggested to be connective tissue-specific nerves. Oval cells with stichopin-LI (OCS) without processes were found in the body-wall dermis, the connective tissue sheath of the longitudinal body-wall muscles, the connective tissue layer of the tube feet and tentacles, and the connective tissue in the radial nerves separating the ectoneural part from the hyponeural part. Electron microscopic observations of the OCSs in the radial nerves showed that they were secretory cells. The OCSs were located either near the well-defined neural structures or near the water-filled cavities, such as the epineural sinus and the canals of the tube feet. The location near the water-filled cavities might suggest that stichopin was secreted into these cavities to function as a hormone.

Diversity in mating behavior of hermaphroditic and male-female Caenorhabditis nematodes.

In this study, we addressed why Caenorhabditis elegans males are inefficient at fertilizing their hermaphrodites. During copulation, hermaphrodites generally move away from males before they become impregnated. C. elegans hermaphrodites reproduce by internal self-fertilization, so that copulation with males is not required for species propagation. The hermaphroditic mode of reproduction could potentially relax selection for genes that optimize male mating behavior. We examined males from hermaphroditic and gonochoristic (male-female copulation) Caenorhabditis species to determine if they use different sensory and motor mechanisms to control their mating behavior. Instead, we found through laser ablation analysis and behavioral observations that hermaphroditic C. briggsae and gonochoristic C. remanei and Caenorhabditis species 4, PB2801 males produce a factor that immobilizes females during copulation. This factor also stimulates the vulval slit to widen, so that the male copulatory spicules can easily insert. C. elegans and C. briggsae hermaphrodites are not affected by this factor. We suggest that sensory and motor execution of mating behavior have not significantly changed among males of different Caenorhabditis species; however, during the evolution of internal self-fertilization, hermaphrodites have lost the ability to respond to the male soporific-inducing factor.

Vagal neural crest contribution to the chick embryo cloaca.

Intrinsic innervation of the developing chick cloaca is provided by the enteric nervous system, a network of neurons and glia that lies within its walls. The enteric nervous system originates from neural crest cells that migrate from the vagal and sacral regions of the neural tube during the early stages of development. Abnormal cloacal development can cause a number of anorectal anomalies including persistent cloaca. Our study aimed to investigate the contribution of vagal neural crest cells to the total population of enteric neurons and glia within the chick embryo cloaca, using quail-chick chimeras. Chicken embryos were incubated until the 10-12 somite stage (ss). The vagal neural tube, corresponding to somites 1-7, was then microsurgically ablated in ovo and isochronic and isotopic quail grafts were performed. The eggs were then reincubated until embryos were harvested at E12. Whole embryos were fixed in Bouin's fluid, embedded in paraffin wax and sectioned. Immunohistochemistry was carried out using the HNK-1 antibody to label all neural crest cells, and the quail-specific antibody, QCPN, to label quail cells. QCPN-immunoreactive cells were seen to make up a large proportion of enteric neurons and glia within the walls of the embryonic cloaca. HNK-1 labelled all neural crest cells in the myenteric and submucosal plexuses as well as the sacral crest-derived nerve of Remak, while QCPN-positive cells were evident in both plexuses but mostly in the submucosal plexus, where they appeared to make up the majority of neurons. Results show that the chick embryo cloaca is primarily innervated by vagal neural crest cells. Further studies to investigate the contribution of sacral neural crest cells to the same region will give further insight into the development of the enteric nervous system within the embryonic cloaca.

Differences in nitrergic innervation of the developing chick cloaca and colorectum.

The intrinsic innervation of the developing gut has long been a subject of investigation, but little is known regarding that of the embryonic cloaca. The cloaca, like the rest of the gastrointestinal tract, is intrinsically innervated by the enteric nervous system. Nitrergic neurons and fibres make up a large part of this system, thus, their distribution provides us with a useful insight into its development. Cloacal and colorectal tissue specimens were removed from chick embryos at embryonic days 11 (E11), E15 and E19. NADPH-diaphorase (NADPH-d) histochemistry was carried out using whole mount tissue preparations. Ganglia density, the number of NADPH-d-positive cells per ganglia in the myenteric plexus and cell size were calculated and statistical analysis was performed to compare both regions of the gut (P<0.001). There were significant differences in the ganglia density in the cloaca compared to the colorectum at E11 (P<0.05) and E15 (P<0.01), with the colorectum having a much denser network. In both the cloaca and the colorectum, ganglia density significantly decreased with age (P<0.001), while significant differences were observed in the number of NADPH-d-positive cells per ganglia in both regions through development. Total cell size was similar in both the cloaca and colorectum at each stage and increased in both regions through development, predominantly due to an increase in the cytoplasm. Results reveal striking differences in innervation between the chick embryo cloaca and colorectum. The sparse network of innervation evident within the cloaca in contrast to the dense network within the colorectum emphasizes the individuality of both regions. These results highlight the need for a further in-depth analysis of the enteric nervous system's development within the embryonic cloaca.

The effect of vagal neural crest ablation on the chick embryo cloaca.

The cloaca, the caudal limit of the avian gastrointestinal tract, acts as a collecting chamber into which the gastrointestinal, urinary, and genital tracts discharge. It is intrinsically innervated by the enteric nervous system, which is derived from neural crest emigres that migrate from the vagal and sacral regions of the neural tube. Abnormal cloacal development can cause a number of anorectal anomalies, including persistent cloaca. Ablation of the vagal neural crest has previously been shown to result in an aganglionic hindgut to the extent of the colorectum. The aim of our study was to investigate the effect of vagal neural crest ablation on the cloaca, the limit of the hindgut in the developing chick embryo. Chick embryos were incubated until the 10-12 somite stage. The vagal neural tube corresponding to the level of somites 3-6 was then ablated, and eggs were incubated until harvested on embryonic day 11 (E11). Whole chick embryos were fixed, embedded in paraffin, and sectioned. Immunohistochemistry was then carried out using the HNK-1 monoclonal antibody to label neural crest cells, and results were assessed by light microscopy. Vagal neural crest ablation resulted in a dramatic decrease in the number of neural crest cells colonizing the chick embryo cloaca compared with control embryos. Ablated embryos contained only a small number of HNK-1-positive neural crest cells, which were scattered within the myenteric plexus in a disorganised pattern. Hypoganglionosis was also evident in other regions of the hindgut in ablated embryos. Ablation of the vagal neural crest results in a hypoganglionic cloaca in addition to hypoganglionosis of the hindgut. These results suggest that the cloaca is largely innervated by vagal neural crest emigres. Further studies involving quail-chick chimeras to investigate the exact contribution provided by both vagal and sacral neural crest cells to the cloaca should increase our understanding of the pathophysiology of conditions like persistent cloaca.

The timing of enteric neural crest cell colonisation of the chick embryo cloaca.

Neural crest cell (NCC) migration and formation of the enteric nervous system (ENS) is an essential process in the development of the normal human gut. Abnormalities of the ENS lead to a number of neurochristopathies. In avian embryos, the cloaca acts as a common chamber into which gastrointestinal, urinary and genital tracts emerge. Previous studies have elucidated the specific timeframes at which NCCs reach the various regions of the developing chick gut but, to date, none have looked at NCC colonisation of the cloaca. The aim of our study was to investigate the exact timing of the appearance of NCCs in the cloaca of chick embryos. Chicken embryos were harvested on embryonic days (E) 8-12. Whole embryos were fixed, embedded in paraffin and sectioned. Fluorescent immunohistochemistry, using an anti-HNK-1/N-CAM monoclonal antibody, was performed and images were obtained by confocal microscopy. There was no evidence of NCCs in the cloaca of embryos from E8 to E11. Intense immunoreactivity to HNK-1 first appeared in the cloaca of E12 embryos, demonstrating a profuse circumferential colonisation by NCCs at this time. Our study is the first to show the exact timing of enteric NCC colonisation of the chick embryo cloaca. Further studies, involving quail-chick chimeras, are required to establish the true origin of cloacal NCCs and to establish the relationship between NCCs and persistent cloaca.

Rapid corticosterone-induced impairment of amplectic clasping occurs in the spinal cord of roughskin newts (taricha granulosa).

Courtship clasping, a reproductive behavior in male roughskin newts (Taricha granulosa), is rapidly blocked by an action of corticosterone (CORT) at a specific neuronal membrane receptor. The CORT-induced impairment of clasping in behaving newts appears to be mediated partly by an elimination of clasping-related activity in medullary reticulospinal neurons. Previous studies of rapid CORT actions in Taricha have focused on the brain, so existence of CORT action in the spinal cord or peripheral nervous system has not been assessed. The present study used newts with a high cervical spinal transection to examine potential spinal or peripheral CORT effects on clasping by the hindlimbs in response to pressure on the cloaca. Spinal transection causes clasps elicited by cloacal stimulation to be very sustained beyond the termination of the eliciting stimulus. In spinally transected newts, CORT caused a dose-dependent depression in the duration as well as quality of the clasp that appeared within 10 min of injection. CORT selectively impaired the usual sustained maintenance of a clasp after termination of cloacal stimulation, but not clasp elicitation during stimulation. These effects were not produced by dexamethasone, a synthetic glucocorticoid that binds poorly to the CORT membrane receptor. The CORT effect on clasp maintenance but not clasp elicitation implies selective action on an intraspinal generator for clasping but not on sensory or efferent neuromuscular aspects of the response. These results indicate the presence in the newt spinal cord of the CORT membrane receptor that exerts functional effects distinctly different from those on the brainstem.

Further observations on the sensitive innervation of some bird's proctodeum.

The AA. studied the autonomic and sensitive somatic innervation of some female bird's proctodeum, through the properly modified Ruffini's gold chloride method. The vegetative component was constituted by ganglion cells of different size, isolated or grouped to form ganglia, found along the course of nerve trunks or in the concurrent point of different nerve bundles. The sensitive somatic innervation was represented by free and encapsulated endings differently distributed in the thickness of the wall. The former were composed of thin networks, while the latter, located more frequently in the muscular tunica and in the subadventitial connective, were composed of encapsulated receptors classified as Pacini, Pacini-like and Herbst corpuscles. The morphology of these receptors was described and hypotheses were brought up about their probable functional role. The AA, also found, even if very rarely, helicoidal collagen fibres around nerve fascicles.

Control of attractivity and receptivity in female red-sided garter snakes.

Female red-sided garter snakes emerge from their hibernacula in the spring attractive and receptive to males. Attractivity is communicated by a pheromone released through the female's skin and is a consequence of ovarian recrudescence the previous summer. Receptivity, on the other hand, is stimulated by ovarian estrogen secretion during emergence itself. Mating renders females both unattractive and unreceptive. Another "mating" pheromone of male origin is important in making females unattractive after mating. To investigate the role of cloacal stimulation in the loss of attractivity and receptivity we injected a local anesthetic (lidocaine or tetracaine) in the cloacal region of females before mating. This does not prevent mating, although it blocks neural transmission of copulatory sensory stimuli. The time course of transition from attractive and receptive states was then observed. Females treated with local anesthetic as well as control females were unattractive within 15 min of mating. However, when retested 2-3 and 24 h after mating, a significantly higher proportion of treated females regained their attractivity, while mated control females remained unattractive. This restorative effect was transient, though, as treated females retested 48 h after mating were as unattractive as the controls. Both anesthetized and control females were unreceptive when tested following mating and did not regain receptivity with time. Last, the mating-induced surge in circulating concentrations of prostaglandin was diminished in females that received a local anesthetic prior to mating. Taken together these results indicate that the loss of attractivity and receptivity following mating in the red-sided garter snake is due to combined effects of a mating pheromone and a physiological, neurally mediated response to the sensation of stimuli associated with the act of mating.

Innervation of NADPH diaphorase-containing neurons correlated with acetylcholinesterase, tyrosine hydroxylase, and neuropeptides in the pigeon cloaca.

The motility of the avian cloaca is under neural control, but little is known about the neural network that accomplishes this function. This present study was designed to determine the distribution of nitric oxide-synthesising neurons in the pigeon cloaca by enzyme histochemistry for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d). NADPH-d-positive staining was seen in the neurons and fibres in the cloaca. The highest density of nerve fibres was noted in the coprodeum and the lowest in the proctodeum. In the coprodeum, NADPH-d neurons were found singly, formed small groups of 2-10 neurons, or were seen in plexuses in the muscle layer, lamina propria, or around the arterioles. Several NADPH-d-positive neurons were also observed in the ganglia of the cloaca. NADPH-d fibres ran in the muscle layer, lamina muscularis mucosae and lamina propria, or surrounded blood vessels. The distribution pattern of acetylcholinesterase (AChE)-stained neurons and fibres in the cloaca was similar to that of NADPH-d. Double staining for NADPH-d and AChE showed colocalisation of the 2 enzymes in many neurons of the cloaca. Tyrosine hydroxylase (TH)-immunoreactive nerve fibres originating outside the cloaca were also noted. In the urodeum and proctodeum, neurons or fibres positive for NADPH-d, AChE or TH were scattered in the lamina propria. Nerve fibres immunoreactive for calcitonin-gene related peptide, galanin, methionine-enkephalin, substance P, and vasoactive intestinal peptide were found sparsely in the cloaca. Our results demonstrate that nitrergic neurons constitute a subpopulation which is closely associated with the cholinergic system in the pigeon cloaca.

Electrical characteristics and responses to jejunal distension of neurons in Remak's juxta-jejunal ganglia of the domestic fowl.

1. Remak's nerve is a ganglionated nerve trunk found only in birds that runs parallel to the gut from the duodenal-jejunal junction to the cloaca. We report the first electrophysiological characterization of these neurons and their responses to gut distension. 2. A segment of chicken jejunum with attached Remak's nerve was pinned in an electrophysiological chamber. Neurons in Remak's ganglia were impaled with microelectrodes. The adjacent segment of gut was distended with fluid. 3. One hundred and thirty neurons were characterized into three electrophysiological classes: (i) tonic neurons (74%) fired action potentials spontaneously (frequency 3.5 Hz) and continuously (up to 40 Hz) throughout a depolarizing current pulse; (ii) AD neurons (22%) fired a brief burst of action potentials (1-10), which were followed by a prolonged after-depolarization (AD) of duration 2.8 +/- 0.3 s; and (iii) phasic neurons (4%) fired an initial burst of action potentials followed by an after-hyperpolarization (duration, 520.0 +/- 32.0 ms). Tetrodotoxin (1 microM) abolished action potentials in tonic and AD neurons as well as the after-depolarization. 4. Spontaneous fast excitatory postsynaptic potentials (FEPSPs) occurred in all classes of neurons; they were not observed, however, in ganglia isolated from the jejunum. 5. Intracellular injection of biocytin revealed that neurons could be characterized into four morphological classes. Tonic neurons, which had long and extensive dendritic trees, were Remak's Type I, II and IV neurons. AD neurons also comprised Remak's type II neurons. Phasic neurons were Remak's Type III neurons. Most neurons had axons that projected orally along Remak's nerve. 6. Distension of the jejunum evoked FEPSPs and action potentials in tonic neurons, and repetitive bursts of action potentials (1-4) followed by an after-depolarization in AD neurons. All responses to distension were blocked by hexamethonium (300 microM) and tetrodotoxin (1 microM). 7. In conclusion, neurons in Remak's juxta-jejunal nerve appear to regulate gut motility. Three distinct electrophysiological classes of neurons were observed, all of which appear to be activated by distension sensitive cholinergic intestinofugal neurons in the jejunum.

The foam production system of the male Japanese quail: characterization of structure and function.

The research described here characterizes a unique neuromuscular system involved in reproductive behavior--the foam production system of the male Japanese quail (Coturnix japonica). Male quail produce a large amount of foam that is transferred to the female during copulation, enhancing male fertilization success. The source is the foam gland complex, a large sexually dimorphic, androgen sensitive, external protuberance of the dorsal cloaca, consisting of glandular units interdigitated with striated muscle fibers of the sphincter cloacae muscle (mSC). Electromyographic (EMG) analysis of mSC activity in freely moving males interacting with females revealed different characteristics of the EMG signal during copulation, voiding of excreta, and other mSC movement. The amount of mSC activity and also the amount of foam produced were greatly increased by the presence of a female behind a screen. Denervation of mSC eliminated normal mSC movement and also abolished foam production, confirming that mSC activity is the mechanism for foam production. The spinal cord locations of the motoneurons innervating the major cloacal muscles, including mSC, were determined by injecting cholera-toxin conjugated horseradish peroxidase into each muscle. Labelled somata with multiple primary dendrites were located in Area IX of the lateral motor column of synsacral segments 7, 8, or 9 or 8, 9, and 10. The motoneurons serving mSC were intermingled with those projecting to the other cloacal muscles, but there were differences in the rostralcaudal placement of these neural populations. Thus mSC activity is an integral part of the male's reproductive behavior, mSC activity can be socially stimulated, and mSC activity occurring in anticipation of copulation is likely to be functionally significant. Continued investigation of this highly accessible system has the potential to shed light on the mechanisms by which complex motor acts are produced and hormonally regulated.

Intrinsic innervation of the chicken lower digestive tract.

We have studied the different components of the enteric nervous system in the rectum and cloaca of the chicken by means of histochemical and immunohistochemical techniques. We found cholinergic neuronal bodies as well as nervous fibers, which constitute part of the Meissner and Auerbach plexuses. We also observed plentiful catecholaminergic fibers in both plexuses, though there were no catecholaminergic neuronal bodies. With respect to the Vasoactive Intestinal Peptide (VIP) and substance P (SP) positive peptidergic innervation, only positive fibers were found, which were less abundant than in the other zones of the gastrointestinal tract. The optic microscopy results were confirmed by electron microscopy.

The spinal segmental and preganglionic projections from the brainstem in relation to the chicken cloaca.

Descending projections from the brainstem to the sympathetic and parasympathetic regions of the chicken spinal cord were investigated by means of the WGA-HRP method. The segmental and preganglionic injections of WGA-HRP were made into spinal segments 20-23 and 30-33 which were sympathetically and parasympathetically related to the cloaca, respectively. After injections of a large amount of WGA-HRP into each level of segments 20-23 and 30-33, the labeled SP-neurons (segmental projection neurons) were distributed mainly in the ventral half of the medulla in both cases. The distribution of these labeled neurons extended mainly to the central (20-23 segmental injections) and the lateral (30-33 segmental injections) tegmental regions of the pons. In the mesencephalon, some SP-neurons were found in the dorsomedial reticular formation and the dorsal midline area, in addition to the Ru in both cases. By iontophoretic microinjections of WGA-HRP into the preganglionic regions of these segments, the labeled preganglionic projection neurons (PP-neurons) were found in the ventromedial part of the medulla. Both distributions of the labeled PP-neurons projecting to the sympathetic and parasympathetic regions were similar in the medulla. In the pons, although the sympathetic PP-neurons were found in the ventromedial pontine tegmentum, most of the parasympathetic PP-neurons were found in the dorsolateral tegmentum, e.g., the LoC-SC region. In the mesencephalon, a few sympathetic PP-neurons were found in the midline area ventromedial to the EW, but no parasympathetic PP-neurons were observed in the mesencephalon.(ABSTRACT TRUNCATED AT 250 WORDS)