The distribution of monoamines in the hypothalamus of the Japanese quail, Coturnix coturnix japonica

Origin and Evolution of the Neuroendocrine Control of Reproduction in Vertebrates, With Special Focus on Genome and Gene Duplications

In humans, as in the other mammals, the neuroendocrine control of reproduction is ensured by the brain-pituitary gonadotropic axis. Multiple internal and environmental cues are integrated via brain neuronal networks, ultimately leading to the modulation of the activity of gonadotropin-releasing hormone (GnRH) neurons. The decapeptide GnRH is released into the hypothalamic-hypophysial portal blood system and stimulates the production of pituitary glycoprotein hormones, the two gonadotropins luteinizing hormone and follicle-stimulating hormone. A novel actor, the neuropeptide kisspeptin, acting upstream of GnRH, has attracted increasing attention in recent years. Other neuropeptides, such as gonadotropin-inhibiting hormone/RF-amide related peptide, and other members of the RF-amide peptide superfamily, as well as various nonpeptidic neuromediators such as dopamine and serotonin also provide a large panel of stimulatory or inhibitory regulators. This paper addresses the origin and evolution of the vertebrate gonadotropic axis. Brain-pituitary neuroendocrine axes are typical of vertebrates, the pituitary gland, mediator and amplifier of brain control on peripheral organs, being a vertebrate innovation. The paper reviews, from molecular and functional perspectives, the evolution across vertebrate radiation of some key actors of the vertebrate neuroendocrine control of reproduction and traces back their origin along the vertebrate lineage and in other metazoa before the emergence of vertebrates. A focus is given on how gene duplications, resulting from either local events or from whole genome duplication events, and followed by paralogous gene loss or conservation, might have shaped the evolutionary scenarios of current families of key actors of the gonadotropic axis.

Effects of catecholamines on ovary morphology, blood concentrations of estradiol-17beta, progesterone, zinc, triglycerides and rate of ovulation in domestic hens

The present study is an attempt to shed more light on the role of epinephrine (EP) and norepinephrine (NE) in regulating ovarian follicular development, folliculogenesis and ovulation in laying hens. Sixty Egyptian local cross females (Mandarah), 50 weeks old, were individually housed and equally divided into three treatments: control (saline, 0.9% NaCl), EP (0.15 mg epinephrine/hen/day) and NE (0.75 mg norepinephrine/hen/day) (n=20). Animals were injected intramuscularly once a day for 15 successive days. At the end of the experimental period, 10 females from each treatment were randomly chosen, weighed and killed by decapitation. Ovaries and oviducts and ovarian follicles were examined. Plasma concentrations of estradiol-17beta, progesterone, zinc and triglyceride were determined. Results indicated that the ovaries of NE- and EP-treated hens were more developed than those of control hens being heavier and containing more yellow yolk-filled follicles. EP or NE significantly increased the ovulation rate and plasma concentrations of estradiol-17beta, progesterone, zinc and triglyceride compared with control treatment. It could be concluded that catecholamines may have a part in promoting ovarian follicular development and in stimulating ovulation in laying hens at the end of their reproductive lives.

Distribution of serotonin-immunoreactivity in the brain of the pigeon (Columba livia)

The distribution of serotonin (5-HT)-containing perikarya, fibers and terminals in the brain of the pigeon (Columba livia) was investigated, using immunohistochemical and immunofluorescence methods combined with retrograde axonal transport. Twenty-one different groups of 5-HT immunoreactive (IR) cells were identified, 2 of which were localized at the hypothalamic level (periventricular organ, infundibular recess) and 19 at the tegmental-mesencephalic and rhombencephalic levels. Ten of the cell groups were situated within the region of the midline from the isthmic to the posterior rhombencephalic level and constituted the raphe system (nucleus annularis, decussatio brachium conjunctivum, area ventralis, external border of the nucleus interpeduncularis, zona peri-nervus oculomotorius, zona perifasciculus longitudinalis medialis, zona inter-flm, nucleus linearis caudalis, nucleus raphe superior pars ventralis, nucleus raphe inferior). The 9 other cell populations belonged to the lateral group and extended from the posterior mesencephalic tegmentum to the caudal rhombencephalon [formatio reticularis mesencephali, nucleus ventrolateralis tegmenti, ectopic area (Ec) of the nucleus isthmo-opticus (NIO), nucleus subceruleus, nucleus ceruleus, nucleus reticularis pontis caudalis, nucleus vestibularis medialis, nucleus reticularis parvocellularis and nucleus reticularis magnocellularis]. Combining the retrograde axonal transport of rhodamine beta-isothiocyanate (RITC) after intraocular injection and immunohistofluorescence (fluoresceine isothiocyanate: FITC/5-HT) showed the centrifugal neurons (NIO, Ec) to be immunonegative. Serotonin-IR fibers and terminals were found to be very broadly distributed within the brain and were particularly prominent in several structures of the telencephalon (archistriatum pars dorsalis, nucleus taeniae, area parahippocampalis, septum), diencephalon (nuclei preopticus medianus, magnocellularis, nucleus geniculatus lateralis pars ventralis, nucleus triangularis, nucleus pretectalis), mesencephalon-rhombencephalon (superficial layers of the optic tectum, nucleus ectomamillaris, nucleus isthmo-opticus and in most of the cranial nerve nuclei). Comparing the present results with those of previous studies in birds suggests some major serotonin-containing pathways in the avian brain and clarifies the possible origin of the serotonin innervation of some parts of the brain. Moreover, comparing our results in birds with those obtained in other vertebrate species shows that the organization of the serotoninergic system in many regions of the avian brain is much like that found in reptiles and mammals.

Noradrenergic system in the chicken brain: immunocytochemical study with antibodies to noradrenaline and dopamine-beta-hydroxylase

A light microscopic immunocytochemical study, using antisera against noradrenaline (NA) and dopamine-beta-hydroxylase (DBH), revealed the noradrenergic system in the brain of the chicken (Gallus domesticus). NA- and DBH-immunoreactive (ir) elements showed a similar distribution throughout the whole brain. The neurons immunoreactive for the monoamine were confined to the lower brainstem, the pons, and the medulla. In the pons, a rather dense group of cells was found in the dorsal, most posterior part of the locus coeruleus and in the caudal nucleus subcoeruleus ventralis. A few labeled cells appeared in and around the nucleus olivaris superior in the most caudal part of the metencephalic tegmentum. In the medulla oblongata, noradrenergic cells could be visualized at the level of the nucleus of the solitary tract and in a ventrolateral complex. Virtually all regions of the brain contained a rather dense innervation by NA- and DBH-immunopositive varicose fibers. Noradrenergic fibers and terminals were especially abundant in the ventral forebrain and in the periventricular hypothalamic regions. DBH-ir and NA-ir fibers, varicosities, and punctate structures could be observed in close association with immunonegative perikarya in several brain regions, more specifically in the ventral telencephalon, in the mid- and tuberal hypothalamic region, and in the dorsal rostral pons. Some perikarya in these brain areas were completely surrounded by noradrenergic structures that formed pericellular arrangements around the cells. The present study on the distribution of the noradrenergic system in the brain of the chicken combined with the results of a previous report on the distribution of L-Dopa and dopamine in the same species (L. Moons, J. van Gils, E. Ghijsels, and F. Vandesande, 1994, J. Comp. Neurol. 346:97-118) offers the opportunity to differentiate between the various catecholamines in the brain of this vertebrate. The results are discussed in relation to catecholaminergic systems previously reported in avian species and in the mammalian brain.

Laminar distribution and sources of catecholaminergic input to the optic tectum of the pigeon (Columbia livia)

A combined immunohistochemical and retrograde tracing approach was used to characterize the catecholaminergic innervation of the optic tectum (TeO), the major target of retinal projections in many avian species. Giemsa counterstaining was employed to determine precisely the laminar localization of immunoreactive fibers and presumptive terminals. The TeO of the pigeon is densely innervated by fibers immunoreactive for tyrosine hydroxylase (TH), which are most heavily distributed to the superficial layers of its dorsal and anterior portions. Within the dorsal-anterior tectum, TH-immunoreactive processes are particularly dense in retinorecipient layers 4 and 7 and in layer 5a. As in the mammalian superior colliculus, the bulk of the catecholaminergic innervation of the pigeon TeO reflects inputs, presumably noradrenergic, originating in the locus coeruleus and nucleus subcoeruleus. However, the catecholaminergic innervation of the pigeon TeO shows several features distinct from those reported for the mammalian superior colliculus. These include an input from a pretectal TH-positive cell group unknown in mammals and the presence of residual TH immunoreactivity after administration of the noradrenergic neurotoxin DSP-4. Moreover, the pattern of TH-immunoreactive fibers in pigeon TeO indicates more laminar and regional specialization within this structure than has been reported for the catecholaminergic innervation of the superior colliculus in mammals.

Cerebrospinal fluid-contacting neurons in the paraventricular organ and in the spinal cord of the quail embryo: a fluorescence-histochemical study

Although the cerebrospinal fluid-contacting neurons of the avian paraventricular organ exhibit considerable amounts of catecholamines, they show no tyrosine hydroxylase immunoreactivity. In the quail embryo, the development of these neurons has been studied using the paraformaldeyde-glutaraldeyde method for the fluorescence-histochemical localization of catecholamines. The timing of the appearance of catecholamine fluorescence in cerebrospinal fluid-contacting neurons and that in catecholamine-containing neurons of the brainstem have been compared. The first neurons displaying catecholamine fluorescence are found within the locus coeruleus and the nucleus subcoeruleus ventralis on the 5.5th day of incubation. Catecholaminergic neuronal groups of the medulla and mesencephalon can be identified by embryonic day 7, and fluorescent cerebrospinal fluid-contacting neurons of the hypothalamic paraventricular organ can be first recognized at the 8th day of incubation. If the catecholamine content of cerebrospinal fluid-contacting neurons that lack tyrosine hydroxylase depends upon an uptake mechanism, it may be significant that, in fluorescence-histochemical preparations, these neurons can be identified 1-3 days later than those in which catecholamines are synthesized and from which catecholamines are released at an earlier developmental stage. Moreover, cerebrospinal fluid-contacting neurons that have previously been shown to be tyrosine-hydroxylase immunoreactive, and that lie at the spinal-medullary junction display a different developmental pattern. By fluorescence histochemistry, they can be detected only by embryonic day 10.5. The chemical, developmental and topographical differences suggest that the catecholamine-containing cerebrospinal fluid-contacting elements of the paraventricular organ and those of the spinal cord represent two different subsets of cerebrospinal fluid-contacting neurons whose respective functional roles remain to be investigated.

Photoperiodic activation of fos-like immunoreactive protein in neurones within the tuberal hypothalamus of Japanese quail

Photoperiodic stimulation of quail (Coturnix coturnix japonica) resulted in the appearance of a nuclear fos-like protein within neurones of the basal tuberal hypothalamus. On transfer to long days the number of neurones containing this fos-like immunoreactivity increased from about 150 to 700, the neurones being scattered throughout the length of the tubero-infundibular complex. This activation had occurred by early in the second long day and was maintained for at least three long days. Over this period circulating levels of LH increased seven-fold, indicating that photoperiodic induction had taken place in the birds. A similar time-course of fos-like induction occurred in castrated quail exposed to a single long day and then returned to short days. Activation mirrored the long-term changes in LH secretion found in this paradigm and fos-like immunoreactivity showed the same "carry-over" characteristics of photoperiodic induction, being maximal two days after the quail had been exposed to the single long day (and were again on short days) and when LH secretion was at its maximum. Activation of fos-like immunoreactive cells did not take place when long-day quail were transferred to short photoperiods. The evidence supports the view that the neurones being activated are involved in a specific fashion in the avian photoperiodic response.

Immunocytochemical localization of L-dopa and dopamine in the brain of the chicken (Gallus domesticus)

A light microscopic immunocytochemical study, with antisera against dihydroxyphenylalanine (L-DOPA) and dopamine (DA), revealed the dopaergic and dopaminergic systems in the brain of the chicken (Gallus domesticus). L-DOPA- and DA-immunoreactive (ir) elements are similarly distributed throughout the entire brain. Virtually all regions of the brain contained a dense innervation by L-DOPA- and DA-immunopositive varicose fibers. The neuronal cell bodies immunoreactive for the two monoamines were confined to more restricted regions, the hypothalamus, the midbrain and the brainstem. In the hypothalamus, DA- and L-DOPA-ir neurons were subdivided into a medial periventricular and a lateral group. The medial group starts at the level of the anterior commissure, in the ventral part of the nucleus periventricularis hypothalami, and continues in a more dorsal periventricular position caudally into the dorsal tuberal hypothalamic region. Densely labeled cerebrospinal fluid contacting cells can be observed in the paraventricular organ. The lateral group consists of immunopositive neurons loosely arranged in the lateral hypothalamic area and in the nucleus mamillaris lateralis. Most of the dopaminergic cell groups, identified in the hypothalamus of mammals, could be observed in the chicken, with the exception of the tuberoinfundibular group. The majority of L-DOPA- and DA-ir perikarya is, however, situated in the mesencephalic tegmentum, in the area ventralis of Tsai and in the nucleus tegmenti pedunculo-pontinus, pars compacta, the avian homologues of, respectively, the ventral tegmental area and the substantia nigra of mammals. In the pons, dense groups of cells are found in the locus coeruleus and in the nucleus subcoeruleus ventralis and dorsalis. A few labeled cells appear in and around the nucleus olivaris superior in the most caudal part of the metencephalic tegmentum. In the medulla oblongata, L-DOPA- and DA-ir cells can be seen at the level of the nucleus of the solitary tract and in a ventrolateral complex. A comparison with tyrosine hydroxylase (TH) immunocytochemistry revealed TH-immunopositive neurons greatly outnumbering the cells exhibiting DA and L-DOPA immunoreactivity. These results are discussed in relation to catecholaminergic systems previously reported in avian species and in the mammalian brain.

The catecholaminergic system of the quail brain: immunocytochemical studies of dopamine beta-hydroxylase and tyrosine hydroxylase

The distribution of dopamine beta-hydroxylase and tyrosine hydroxylase, two key enzymes in the biosynthesis of catecholamines, was investigated by immunocytochemistry in the brain of male and female Japanese quail. Cells or fibers showing dopamine beta-hydroxylase and tyrosine hydroxylase immunoreactivity were considered to be noradrenergic or adrenergic, while all structures showing only tyrosine hydroxylase immunoreactivity were tentatively considered to be dopaminergic. The major dopaminergic and noradrenergic cell groups that have been identified in the brain of mammals could be observed in the Japanese quail, with the exception of a tuberoinfundibular dopaminergic group. The dopamine beta-hydroxylase-immunoreactive cells were found exclusively in the pons (locus ceruleus and nucleus subceruleus ventralis) and in the medulla (area of the nucleus reticularis). The tyrosine hydroxylase-immunoreactive cells had a much wider distribution and extended from the preoptic area to the level of the medulla. They were, however, present in larger numbers in the area ventralis of Tsai and in the nucleus tegmenti pedunculo-pontinus, pars compacta, which respectively correspond to the ventral tegmental area and to the substantia nigra of mammals. A high density of dopamine beta-hydroxylase- and tyrosine hydroxylase-immunoreactive fibers and punctate structures was found in several steroid-sensitive brain regions that are implicated in the control of reproduction. In the preoptic area and in the region of the nucleus accumbens-nucleus stria terminalis, immunonegative perikarya were completely surrounded by immunoreactive fibers forming basket-like structures. Given that some of these cells contain the enzyme aromatase, these structures may represent the morphological substrate for a regulation of aromatase activity by catecholamines. The dopamine beta-hydroxylase-immunoreactive fibers were also present in a larger part of the preoptic area of females than in males. This sex difference in the noradrenergic innervation of the preoptic area presumably reflects the sex difference in norepinephrine content in this region.

Immunocytochemical demonstration of serotonin-immunoreactive cerebrospinal fluid-contacting neurons in the paraventricular organ of pigeons and domestic chickens

The paraventricular organs (PVO) of the pigeon and domestic chicken contain at least three types of serotonin-immunoreactive (serotonin-ir) CSF-contacting neurons. Type 1 neurons were predominant. They had two bipolar extending processes. The somata were mostly found in the pars hypendymalis. Type 2 neurons were characterized by thin and long apical processes. Their perikarya were found in the pars distalis of the PVO or the more lateral area of this organ. Type 3 neurons were considerably smaller and had round somata. They were mostly bipolar with thin and short dendritic processes and thin basal processes. A small number of this type was conspicuous along the cranial peripheral region of the PVO. In addition to the PVO area, aggregations of small, bipolar serotonin-ir CSF-contacting neurons were shown in the most caudal wall of the third ventricle of both species, distributed medially or paramedially. Immunoelectron microscopy revealed many dense granules in apical ventricular processes and perikarya. Synaptic connections were frequently observed on basal processes.

The serotoninergic system in the brain of the Japanese quail. An immunohistochemical study

The presence and topographical localization of the serotoninergic system in the brain of the Japanese quail (Coturnix coturnix japonica) have been studied by means of peroxidase-anti-peroxidase immunocytochemistry. The perimeter, diameter, area, and shape factor of immunoreactive cells have been recorded and analyzed morphometrically for intra- and interspecies comparison. The data reported here confirm and extend results previously obtained in the brain of other avian species. Serotonin-immunoreactive neurons of the quail are mainly located in the hypothalamic paraventricular organ and adjacent areas, and in the brainstem where they form three separate groups. The first of these groups consists of small-sized neurons located in the ventro-rostral mesencephalon. The second group is composed of medium-sized neurons located in the dorsal mesencephalo-pontine region. The third group is also formed by medium-sized neurons, and is located ventrally in the ponto-medullary region. In the quail brain, serotoninergic neurons are not restricted to nuclei located in the vicinity of the midsagittal plane, but show some lateralization, especially in the brainstem. The organization of the different groups of immunoreactive neurons based on this topographical distribution and morphometric analysis has been compared with descriptions of the serotoninergic system in other birds. Serotonin-immunoreactive nerve fibers are widely distributed throughout the brain, but appear to be particularly abundant in regions involved in the control of reproductive activities, such as the septal region, the medial preoptic nucleus, the nucleus intercollicularis, and the external zone of the median eminence. The data reported here have allowed the drawing of a map of serotonin-immunoreactive structures.

Distribution of alpha 2-adrenergic receptors in the brain of the Japanese quail as determined by quantitative autoradiography: implications for the control of sexually dimorphic reproductive processes

With the use of [3H]p-aminoclonidine (PAC), alpha 2-adrenergic binding sites were mapped in the brain of the Japanese quail (Coturnix coturnix japonica). The sites were labeled with the use of in vitro quantitative autoradiography. Special attention was given to areas implicated in the control of sexually dimorphic reproductive processes including sexual behavior. Preliminary competition experiments found that [3H]PAC binding on tissue sections exhibited a pharmacology appropriate to the alpha 2 receptor. Binding sites were found to be heterogeneously distributed throughout the brain. Some of the highest levels of specific binding were found in several areas regulating reproductive function such as the preoptic area, the supraoptic nucleus, the infundibulum, and the medial mammillary nucleus of the infundibulum. [3H]PAC labeled precisely the morphologically dimorphic preoptic medial nucleus but no sexual dimorphism in density of receptor binding was identified. However, dimorphism in density of receptor binding was identified in two areas: the medial mammillary nucleus and the mesencephalic intercollicular nucleus. The former area appears to be involved in the regulation of gonadotrophin secretion and the latter area has been implicated in the control of vocal behavior. These neurochemical dimorphisms may contribute to the regulation of two sexually dimorphic reproductive processes, gonadotropin secretion and courtship vocalizations.

Sexual differentiation of neuroendocrine systems and behavior

Differentiation of the reproductive system occurs in stages, with early development of the gonads and later differentiation of the brain. The physiological mechanisms that are involved in the sequence of events during sexual differentiation have not been clearly understood. However, recent technological advances have made understanding these mechanisms much more accessible. Many of these techniques have been used to elucidate the nature of steroid-induced effects on target tissues, hormonal and neuroendocrine interactions, and the molecular basis of these processes. This review will focus on the sequence of events and mechanisms associated with sexual differentiation of endocrine, morphological, and behavioral components of reproduction in the chicken and Japanese quail.

Serotonergic modulation of ingestive behavior in pigeons

The effects of peripheral administration of the serotonin agonist zimeldine and the serotonin antagonist cyproheptadine on food and water consumption were evaluated in domestic pigeons. Injections of zimeldine reduced the amount of feeding and drinking dose-dependently in 24-hr fasted animals. Administration of cyproheptadine enhanced food and water consumption dose-dependently up to a dose of 160 micrograms per 100 g body weight in nondeprived pigeons. Higher doses reduced ingestion probably due to a general behavioral depression. The effect of zimeldine was antagonized by cyproheptadine. It is concluded that, as in mammals, serotonin participates as an inhibitor in the regulation of feeding in birds. Contrary to the situation in mammals it has no activating effect on drinking but leads to a reduction of water consumption in pigeons.

Distribution of serotonin immunoreactivity in the forebrain and midbrain of the lizard Gekko gecko

The distribution of serotonin (5-hydroxytryptamine, 5-HT) in the forebrain and midbrain of the lizard Gekko gecko was studied by means of antibodies against serotonin. In the diencephalon, serotonin-immunoreactive (5-HTi) cell bodies were found in the hypothalamic periventricular organ and the ependymal wall of the infundibular recess. In the midbrain, 5-HTi cells were observed in the nucleus raphes superior and the lateral portion of the nucleus reticularis superior. In addition, 5-HTi cell bodies were found lateral to the ventral interpeduncular nucleus and around the ventral aspect of the medial longitudinal fasciculus. Serotonin-immunoreactive fibers and varicosities are present throughout the forebrain and the midbrain, but particularly in the nucleus accumbens, the septal area, the dorsal cortex, the dorsal thalamus, the lateral geniculate body, the ventromedial hypothalamic nucleus, the pretectal nucleus, and the basal optic nucleus. The medial habenular nucleus contains a dense 5-HTi plexus that shows a patchlike pattern. A laminar organization of 5-HTi fibers and varicosities is present in the midbrain tectum. When compared with data obtained in other vertebrates, the present study has confirmed that in the phylogenetic series fishes-amphibians-reptiles-birds-mammals there appears to be (1) a gradual decrease in the number of cerebrospinal-fluid-contacting serotoninergic cells in the hypothalamic periventricular layer and (2) a remarkable increase in number of serotoninergic cells in the midbrain tegmentum. As in mammals, a strong serotoninergic innervation of structures related to sensory, in particular visual, pathways could be recognized.

Distribution of tyrosine-hydroxylase (TH)-immunoreactive neurons in the diencephalon of the pigeon (Columba livia domestica)

The distribution of tyrosine-hydroxylase (TH)-immunoreactive cell bodies and fibers in the diencephalon has been investigated with immunohistological techniques in the pigeon. The results suggest that TH is present in a number of morphologically distinct neuronal systems. Preoptic and hypothalamic TH neurons were subdivided into a medial periventricular and a lateral group. The medial group starts with a rostral collection of small cells in the preoptic region. A significantly larger collection of TH neurons occupies the paraventricular nucleus (PVN) (stratum cellulare internum) and mainly consists of large multipolar cells. Further caudally, the main concentration of cells is in the hypothalamic posteromedial and the periventricular regions of the tuberoinfundibular (arcuate) nucleus. No TH neuron was found in the ventral and lateral parts of the tuberoinfundibular region, suggesting that the prominent tuberoinfundibular dopaminergic system described in mammals is absent in the pigeon. This further substantiated by the relative scarcity of TH immunoreactive fibers and varicosities in the neurohemal zone of the median eminence (ME). The caudalmost components of the medial group appear to be continuous with the large population of TH neurons distributed in the midline of the mesencephalon. Tyrosine-hydroxylase-immunopositive cells have not been found in the paraventricular organ. The lateral group consists of TH neurons loosely arranged in the lateral hypothalamus, including regions of the supraoptic nucleus and hypothalamic posterolateral nucleus. Tyrosine-hydroxylase containing neurons vary widely in size, shape, and dendritic arborization in each diencephalic region. However, it is possible to distinguish two main cell types. Small bipolar neurons with two simple arborizing dendrites were concentrated in the medial periventricular system. The second type of cell is large, multipolar with four to five branching dendrites. This latter cell type occurs mainly in the lateral system and in the PVN. Major fiber bundles containing TH immunoreactivity were identified in the lateral and periventricular hypothalamus. The paraventricular organ and the organum vasculosum laminae terminalis contained the densest arborization of fibers and varicosities. In the ME, dense innervation was found in the subependymal layer. Dense arborizations of TH positive fibers and varicosities were located in the septal nuclei and the paleostriatum augmentatum.

Regional distribution of catecholaminergic terminals in the pigeon visual system

A glyoxilic acid histofluorescence technique was used in this study to determine the distribution of catecholaminergic (CA) terminals in the pigeon visual areas. Our results show that the main visual structures are under the influence of CA nuclei of the brain stem. In particular, the pigeon Wulst, like the mammalian visual cortex, is profusely innervated by CA terminals. In fact, dense CA afferents, most likely noradrenergic (NA) terminals, were found in the hyperstriatum intercalatus superior and the nucleus intercalatus hyperstriati accessorii; area which represent the terminal zone of the retino-thalamo-hyperstriatal pathway. These results suggest a possible convergence of NA terminals and visual fibers on common target cells in the Wulst.

The developmental distribution of monoamines in the brain of male Japanese quail (Coturnix coturnix japonica)

Changes in the levels of the brain catecholamines, norepinephrine (NE) and dopamine (DA), were studied in the male Japanese quail during maturation. In addition the neurotransmitter, serotonin (5HT), its precursor, tryptophan ( TRYP ), and its metabolite, 5-hydroxyindoleacetic acid (5HIAA), were measured. Birds were sampled at weekly intervals between the ages of 1 and 63 days of age. Brains of the quail were dissected into cerebral hemispheres, diencephalon, brain stem, cerebellum, and optic lobes. Spectrophotofluorometric analyses of the monoamines in the brain parts were performed following the validation of this technique for use with the avian brain. Norepinephrine increased significantly (P less than .05) with age in all brain regions except the cerebellum, whereas dopamine increased significantly (P less than .05) only in the cerebral hemispheres. Serotonin levels increased significantly (P less than .05) in all brain regions except the cerebellum. The most dramatic change over maturation was observed in the cerebral hemispheres, and relatively smaller increases occurred in the diencephalon. Tryptophan decreased significantly (P less than .05) in concentration in all brain regions throughout the 9 weeks of development. However, 5HIAA did not change significantly in brain regions. Serum testosterone, as measured by testosterone radioimmunoassay, increased in conjunction with sexual maturation. In general, the monoamine levels rose with age. Additionally, the monoamine distribution appeared to increase in caudal to rostral direction. Changes in the monoamines, particularly in the diencephalon, occurred at approximately the time that increased peripheral concentrations of testosterone were also observed. This observation supports the contention that monoamines may be involved in regulating gonadotropin release during maturation.

Effect of acute stress on catecholamine content in the hypothalamic nuclei of Japanese quail

Concentration of noradrenaline, adrenaline and dopamine in eight hypothalamic nuclei or areas (nucleus hypothalamicus medialis anterior, n. periventricularis magnocellularis, n. hypothalamicus lateralis anterior, n. hypothalamicus medialis posterior, n. hypothalamicus lateralis posterior, eminentia medialis, n. tuberis, area hypothalamica posterior) have been determined by a sensitive radioenzymatic micromethod in male Japanese quail restrained for 30 min. In control quail the highest concentrations were found in the a. hypothalamica posterior, n. periventricularis magnocellularis and n. hypothalamicus medialis anterior; the lowest was in the n. hypothalamicus medialis posterior. After restraint, noradrenaline concentrations decreased in the n. periventricularis magnocellularis and n. hypothalamicus medialis posterior. However, the concentration of adrenaline increased in the n. tuberis under the same conditions. In stressed animals the dopamine concentration was lower than in controls in the n. periventicularis and higher in the n. tuberis.

Serotonin in the brain of the goldfish, Carassius auratus. An immunocytochemical study

The distribution of immunoreactive serotonin (5-HT) was investigated in the brain and pituitary gland of the goldfish with the use of indirect immunofluorescence technique. Immunoreactive cerebrospinal fluid-contacting neurons were found in the nucleus recessus lateralis and in the nucleus recessus posterioris of the hypothalamus. Additional immunoreactive neurons were observed ventro-lateral to the posterior commissure in the nucleus dorsolateralis thalami. This group of cell bodies extends posteriorly as far as the rostral midbrain tegmentum. At the level of the isthmus, numerous immunoreactive cell bodies were located medially between the fiber bundles of the fasciculus longitudinalis medialis. Finally, a few isolated immunoreactive cells were observed in the medulla oblongata. In the pituitary gland, immunoreactive fibers and cells were found primarily in the pars distalis. The origin of the numerous fibers of the telencephalon is not clear, however, they may arise from the perikarya located in the raphe region. The general organization of the ascending and descending 5-HT-systems of the teleost brain appears to be similar to that described in mammals.

Pharmacological studies on the noradrenergic control of luteinizing hormone secretion in the domestic fowl

A neuropharmacological approach was utilized in order to investigate catecholaminergic involvement in the control of LH secretion in the domestic fowl. Inhibition of catecholamine synthesis by alpha-methyl-p-tyrosine (alpha Mpt) at several doses was accompanied by significant reductions in the circulating LH concentration of 6-week-old male cockerels. Plasma LH was similarly depressed following the selective inhibition of NE synthesis by either diethyldithiocarbamate (DDC) or FLA 63. Blockade of alpha 1-adrenergic receptors with phenoxybenzamine was consistently associated with precipitous declines in plasma LH concentrations. Stimulation of alpha-adrenergic receptors by phenylephrine and clonidine elevated circulating LH levels. Activation of the dopaminergic system by apomorphine depressed LH release. However, pimozide was without effect. These data suggest that norepinephrine is involved in the stimulation of LH release, while dopamine may exert an inhibitory influence. Evidence of some stimulatory beta-adrenergic effect is also described.

Immunohistochemical demonstration of serotonin-containing CSF-contacting neurons in the submammalian paraventricular organ

The distribution and morphological aspects of the serotonin-containing neurons in the paraventricular organ of the carp, frog, turtle and chicken were studied by means of an immunoperoxidase technique using serotonin antiserum. In all species the serotonin-containing neurons were seen to have the appearance of the CSF-contacting neurons and to be distributed in the pars ependymalis and the pars hypendymalis of the organ. Particularly, in the frog, the serotonin-containing CSF-contacting neurons, mostly bipolar in shape, were also observed in the pars distalis. Their proximal processes protruded into the ventricular lumen through the ependymal layer with a globular- and triangular-shape. The distal processes projected ependymofugally to the pars distalis and formed a fine plexus in the neuropil of this part. The density of the serotonin fibers in the pars distalis was greater in the carp than in the other species.

Catecholamine-containing neurons in the mesencephalic tegmentum of the chicken. Light, fluorescence and electron microscopic studies

The nucleus tegmentalis dorsalis (NTD) which may be homologous with the mammalian locus coeruleus was investigated in the chicken by means of light, fluorescence and electron microscopy. Results are summarized as follows: 1) Numerous neurons emitting green fluorescence by the Falck-Hillarp method were observed in the NTD of the chicken. By consecutive light and fluorescence microscopy on the same section it was established that these catecholamine(CA)-containing neurons clearly coincided with the cell group named nucleus tegmentalis dorsalis by Jungherr (1945). This procedure further showed that there were also non-fluorescent neurons in the NTD. 2) On the basis of electron microscopic observation, two types of neurons were recognized in the NTD: medium-(15-25 microns) and small-sized (10-15 microns) neurons. Medium-sized neurons had a round to oval nucleus with several deep infoldings and abundant organelles. From combined fluorescence and electron microscopic examination, they obviously corresponded with CA-containing neurons demonstrated by the Falck-Hillarp method. Small-sized neurons had a round nucleus surrounded by pale cytoplasm. They corresponded with non-CA-containing neurons. 3) From morphometric analysis, it was clear that CA-containing neurons contained a well-developed rough-surfaced endoplasmic reticulum and many lysosome-like dense bodies, unlike non-CA-containing neurons. This study was undertaken as the basis of a research program to elucidate the catecholaminergic projections from the NTD.

Topographic, morphologic and developmental characterization of the nucleus loci coerulei in the chicken. A Golgi and fluorescence-histochemical study

Golgi- and fluorescence-histochemical studies in the chicken shown the presence of a sharply delimited group of aminergic neurons beneath the floor of the fourth ventricle at the mesen-metencephalic boundary. According to the observations reported in other avian species a homology can be established between the mammalian locus coeruleus (LC) and this fluorescent cell mass of the chicken brainstem. Golgi studies revealed an isodendritic pattern of ramification of the neurons in this nucleus. In addition, a developmental study on the morphological maturation of the LC in the chick embryo was carried out by means of the histochemical-fluorescence method for biogenic amines and the rapid Golgi method. The time of the first onset of catecholamine synthesis and storage has been shown to correspond to the 9th day of incubation (stage HH 35), just when these cells display a well-established and peculiar dendritic pattern. All maturational events in the LC of the chick embryo thus occur earlier than in the fetal rat brain, the prenatal development of which is accomplished in a period of comparable length.

Topographic atlas of somatostatin-containing neurons system in the avian brain in relation to catecholamine-containing neurons system. I. Telencephalon and diencephalon

The morphological organization of the somatostatin (SRIF)-positive neurons in the forebrain (telencephalon and diencephalon) of the warbling grass parakeet (Melopsittacus undulatus) was studied using the indirect immunohistochemical technique of Coons and co-workers ('58). In the telencephalon, a number of SRIF-positive neurons was detected in the lobus paraolfactorius, hippocampus, and paleostriatum. Furthermore, scattered SRIF-labeled cells were noticed in the area corticoidea dorsolateralis and area temporoparieto-occipitalis. A moderate density of immunoreactive fibers was found in the above areas. In addition, although the septal areas was devoid of SRIF-positive neurons, this area contained a moderate occurred in the following hypothalamic areas: (1) nucleus medialis hypothalami posterior, (2) lateral hypothalamus, and (3) mammillary nucleus. The bird hypothalamus also received a strikingly massive SRIF innervation. The heaviest concentration of SRIF-labeled fibers was detected in the medial eminence. Many SRIF-labeled fibers were also observed in other hypothalamic regions. Their locations roughly corresponded in many cases to the areas in which SRIF-positive neurons were disclosed. The overall distribution of the catecholamine system (CA) of the avian forebrain is also represented by means of histofluorescent technique. A possible interaction between SRIF and CA neurons systems is briefly discussed.

Involvement of catecholaminergic nerve fibers in angiotensin II-induced drinking in the Japanese quail, Coturnix coturnix japonica

Monamine distribution in a septohypothalamic area was investigated in the Japanese quail using a histochemical fluorescence method. This area includes the subfornical organ (SFO) and the preoptic area (POA) which are inferred dipsogenic receptor sites for angiotensin II (AII) in the Japanese quail. Nerve fibers showing yellow-green fluorescence were found between the POA and the SFO. Thwy traversed from the POA to the SFO, and some fibers seemed to terminate on the neurons in the SFO. After a low dose of reserpine, a considerable number of fluorescent perikarya were found in the POA. These fibers and perikarya appeared to be of primary catecholamine judging from the fluorescence color. Following transection of these fibers, fluorescence disappeared from the fibers located on the SFO side of the transection plane, while it became a little more intense on the POA side. After transection, microinjection of AII into the POA was no longer effective in induction of drinking. On the other hand, sham operation or transection in areas other than between the POA and the SFO produced only minute changes in those fluorescent fibers and had little effect on the dipsogenic potency of AII injected into the POA. These results suggest that information of AII perceived at the POA is transferred to the SFO via those primary catecholamine-containing nerve fibers, which effect induced drinking.

The hypothalamic neurosecretory systems of the Japanese quail as revealed by retrograde transport of horseradish peroxidase

Within 24-48 h after injection of horseradish peroxidase (HRP) into the neural lobe or into the median eminence of adult Japanese quail dense accumulations of its reaction product (HRP-RP) can be demonstrated in axons of the hypothalamo-hypophysial tract and in the magnocellular neurosecretory perikarya of the supraoptic and paraventricular nuclei as well as in scattered neurons of the accessory hypothalamic neurosecretory nuclei. The HRP-RP-containing nerve fibers, which are beaded in appearance, occur prominently in the internal zone of the median eminence. They turn dorsally at its anterior border to become widely distributed in the retrochiasmatic region and extended to the paraventricular, supraoptic areas. These observations confirm more directly conclusions drawn earlier from Gomori-type preparations and from immunologic demonstration of arginine vasotocin, mesotocin and neurophysin. HRP-RP was also found in perikarya of parvocellular secretory neurons in the infundibular nucleus 48 h after injection of HRP into the median eminence but not after injection into the pars nervosa. This provides direct evidence that a conspicuous component of the tubero-infundibular tract is formed by axons of tuberal neurons that originate from the infundibular nucleus and pass directly into the median eminence.

Effect of restraint upon hypothalamic and adrenal catecholamines in Japanese quail

1. Changes in catecholamine concentration after periods of restraint up to 48 h in male Japanese quail have been measured. 2. Hypothalamic catecholamines decreased after 10 min restraint. Dopamine concentration increased after 4 h and persisted to 48 h. 3. Plasma catecholamines increased after 10 min, remained high for 2 h and then decreased despite continuing restraint. Catecholamine content of adrenals slightly decreased during restraint. 4. The activity of adrenal phenylethanolamine-N-methyl transferase increased from the 4th hour of restraint.

Monoamine fluorescence in the median eminence of the Japanese quail, Coturnix coturnix japonica, following medial basal hypothalamic deafferentation

Monoamine fluorescence was examined in the ventral hypothalamus of the Japanese quail, Coturnix coturnix japonica after medial basal hypothalamic deafferentation. In sham-operated control birds, numerous yellow-green fluorescent fibers were observed in the median eminence and the nucleus tuberis. In the area of the paraventricular organ, a number of fluorescent fibers and cell bodies were observed. In birds with deafferented hypothalami, fluorescence disappeared both in the median eminence and the nucleus tuberis. In the area of the paraventricular organ, which was within the area of deafferentation, fluorescence of neuronal perikarya did not change, but fluorescent fibers decreased markedly in number. Disappearance of monoamine fluorescence in the median eminence and the nucleus tuberis is discussed in relation to the tanycyte absorptive function and gonadaly development.

Characterization of an unusual catecholamine-containing cell type in the toad hypothalamus. A correlated ultrastructural and fluorescence histochemical study

A nucleus of catecholamine-containing cells bordering the preoptic recess of the toad hypothalamus has been studied by both fluorescence histochemical and electron microscopic methods. The perikarya of these cells form one to three rows immediately subjacent to the ependyma. They send brightly fluorescent apical processes between the ependymal cells to the ventricular surface, and also give rise to long basal processes, the proximal portions of which are also fluorescent. These cells contain two distinctive constitutents: juxtanuclear bundles of tightly packed filaments, the members of which are separated from one another by only approximately 100 A, and large numbers of dense-cored vesicles (400-2200 A in diameter), which appear to arise from an agranular tubular reticulum distinct from the Golgi apparatus. Axons containing either clear vesicles alone or clear and dense-cored vesicles form synapses on the subependymal cells, but no evidence has been found that the subependymal cells themselves form presynaptic contacts, or that axons originate from them. The cytological characteristics of these catecholamine-containing cells, plus the fact that they border directly on the cerebrospinal fluid, suggest that they may be more closely related to peripheral chromaffin cells than to the other cell types intrinsic to the central nervous system, and the name "encephalo-chromaffin cells" is therefore proposed for them. The possible functions of such cells in the central nervous system are discussed.