Distribution of proenkephalin-derived peptides in the brain of Rana esculenta

The immunocytochemical distribution of authentic proenkephalin-containing perikarya and nerve fibers in the brain of Rana esculenta was determined with antisera directed toward different epitopes of preproenkephalin. The pattern of proenkephalinlike immunoreactivity was similar with antisera directed toward [Met5]-enkephalin, [Met5]-enkephalin-Arg6, [Met5]-enkephalin-Arg6-Phe7, [Leu5]-enkephalin, and metorphamide; however, the intensity of the labelling varied depending on the target antigen. Proenkephalin-containing perikarya were located in all major subdivisions of the brain except the metencephalon. In the telencephalon, immunoreactive perikarya were detected in the dorsal, medial, and lateral pallium; the medial septal nucleus; the dorsal and ventral striatum; and the amygdala. In the diencephalon, immunoreactive perikarya were detected in the preoptic nucleus, in the dorsal and ventral caudal hypothalamus, and in an area that appeared to be homologous to the paraventricular nucleus. In the mesencephalon, numerous immunoreactive perikarya were detected in layer 6 of the optic tectum and a few scattered perikarya were detected in layer 4 of the optic tectum. Immunoreactive perikarya also occurred in the laminar nucleus of the torus semicircularis. In the rhombencephalon, immunoreactive perikarya were detected in the obex region and the nucleus of the solitary tract. Immunoreactive fibers of varying density were observed in all major subdivisions of the brain with the densest accumulations of fibers occurring in the dorsal pallium, the lateral and medial forebrain bundles, the amygdala, the periventricular hypothalamus, the superficial region of the caudolateral brainstem, and in a tract that appeared to be homologous to the tractus solitarius. The extensive system of proenkephalin-containing perikarya and nerve fibers in the brain of an amphibian showed many similarities to the distribution of proenkephalin-containing perikarya and nerve fibers previously described for the amniote brain.     

Distribution of proneuropeptide Y-derived peptides in the brain of Rana esculenta and Xenopus laevis

The distribution ofproneuropeptide Y-containing perikarya and nerve fibers in the brain of Rana esculenta and Xenopus lavis was determined with antisera directed toward neuropeptide Y and the carboxyl terminal flanking peptide. The distribution of proneuropeptide Y-like immunoreactivity was similar in both anurans. In the telencephalon, immunoreactive perikarya were found in the olfactory bulb, all subdivisions of the pallium, the septum, pars lateralis of the amygdala, the nucleus accumbens, and the anterior preoptic area. In the diencephalon, labelled perikarya were detected in the ventromedial, ventrolateral and central thalamic nuclei, the magnocellular preoptic nucleus, the suprachiasmatic nucleus, the posterior tuberculum, and the infundibulum. Amacrine-like cells were stained in the retina. In the pretectal area, posterior thalamic neurons showed intense, Golgi-like immunostaining. In the mesencephalon, immunoreactive cells were found in the reticular nucleus, the anteroventral tegmental nucleus, the optic tectum, the interpeduncular nucleus, and the torus semicircularis. In the rhombencephalon, labelled perikarya were detected in the secondary visceral nucleus, the central gray, the nucleus of the solitary tract, the dorsal column nuclei, and the spinal nucleus of the trigeminal nerve. Immunoreactive nerve fibers were observed in all areas of the brain that contained labelled perikarya. The densest accumulations were found in the accessory olfactory bulb, pars lateralis of the amygdala, the ventral habenula, the posterior pituitary, the optic tectum, the interpeduncular nucleus, and the saccular nucleus. The distribution of proneuropeptide Y-like immunoreactivity in the anuran brain showed many similarities to the distribution described for the amniote brain. © 1993 Wiley-Liss, Inc.     

Distribution of neuromedin U-like immunoreactivity in the central nervous system of Rana esculenta

The distribution of perikarya and nerve fibers containing neuromedin U-like immunoreactivity in the brain of Rana esculenta was determined with an antiserum directed toward the carboxyl terminus of the peptide. In the telencephalon, immunoreactive perikarya were found in the olfactory bulb, the medial septum, and the diagonal band. In the diencephalon, labeled perikarya were detected in the anterior and posterior preoptic areas, the dorsal nucleus of the hypothalamus, the caudal part of the infundibulum, and the posterior tuberculum. In the mesencephalon, immunoreactive cell bodies were found only in the laminar nucleus of the torus semicircularis and the anterodorsal tegmental nucleus. In the rhombencephalon, labeled perikarya were detected in the secondary visceral nucleus, the cerebellar nucleus, the central gray, and the nucleus of the solitary tract. Immunoreactive nerve fibers were observed in all areas of the brain that contained labeled perikarya. The densest accumulations were found in the nucleus accumbens; the dorsal part of the lateral septum; the periventricular region of the ventral thalamus; the lateral part of the infundibulum; the anterodorsal, anteroventral, posterodorsal, and posteroventral tegmental nuclei; and the periaqueductal region of the tegmentum. The distribution of neuromedin U-like immunoreactivity in the frog brain was substantially different from the distribution described for the rodent brain. © 1996 Wiley-Liss, Inc.     

Sexually dimorphic distribution of a galanin-like peptide in the central nervous system of the teleost fish Poecilia latipinna.

Immunohistochemical techniques were used to visualize areas of the brain and spinal cord containing a galanin-like peptide in the teleost fish, the sailfin molly. Galanin-like immunoreactivity (GAL-LI) in both males and females was identified in neurons in the nucleus preopticus periventricularis, nucleus lateralis tuberis, and nucleus commissuralis. GAL-LI fibers had a comparable distribution in the forebrain, preoptic, hypothalamic, and visceral sensory areas of both sexes. In striking contrast to these areas, the optic tectum, torus semicircularis, brainstem tegmentum, and spinal cord of the male contained much higher levels of GAL-LI than the female. GAL-LI in these dimorphic areas in the female was limited to single fiber bundles in the ventromedial tegmentum and in the trigeminal system. Additionally, a population of neurons in the preoptic nucleus was found to contain GAL-LI in the male only. Sexual dimorphism was especially prominent in the spinal cord, where extensive GAL-LI fibers were found in the male only. These fibers were oriented in the longitudinal plane and confined largely to the gray matter. Comparative studies were performed on the goldfish spinal cord, in which GAL-LI was localized solely in the dorsal horn and exhibited no sexual dimorphism. Further, examination of spinal cord material from neonatal mollies revealed a lack of spinal GAL-LI at this developmental stage. As the extent of GAL-LI in the male molly spinal cord differs from both the goldfish and from that reported for the mammalian spinal cord, and a prominent sexual dimorphism in GAL-LI extends from the diencephalon to the caudal spinal cord, it is suggested that a galanin-like peptide may play a unique, sex-specific role in this species.     

Distribution of galanin-like immunoreactivity in the brain of the turtle Mauremys caspica

Galanin is a brain-gut peptide present in the central nervous system of fish, amphibians, birds, and mammals. For comparative studies among vertebrates, the distribution of galanin in the brain of reptiles has been investigated. We studied the localization of galanin-like-immunoreactive perikarya and nerve fibers in the brain of the turtle Mauremys caspica by using an antiserum against porcine galanin. In the telencephalon, few immunoreactive perikarya were seen in the amygdaloid complex. The diencephalon contained the majority of the immunoreactive perikarya present in the lamina terminalis, nucleus periventricularis anterior, lateral preoptic area, nuclei hypothalamicus ventromedialis and posterior, nucleus basalis of the anterior commissure, and nucleus ventralis tuberis. Many immunoreactive cells, especially in the infundibulum, contacted the cerebrospinal fluid by an apical process. In the rhomben-cephalon, immunopositive perikarya were restricted to a few cells in the nucleus tractus solitari. In the mesencephalon, they were absent. Immunoreactive nerve fibers were present in all regions containing labeled perikarya and in (1) telencephalon: septum, nucleus fasciculi diagonalis Brocae; (2) diencephalon: nucleus paraventricularis, nucleus supraopticus, nucleus suprachiasmaticus, subventricular grey, nucleus of the paraventricular organ, nucleus mamillaris, infundibular decussation, outer layer of the median eminence, posterior commissure and subcommissural organ region, habenula, nuclei dorsomedialis anterior, and dorsolateralis anterior of the thalamus; and (3) mesencephalon and rhombencephalon: stratum griseum periventriculare, stratum fibrosum periventriculare, laminar nucleus of the torus semicircularis, periventricular grey, nucleus interpeduncularis, nucleus ruber, substantia nigra, locus coeruleus, raphe nuclei, nuclei of the reticular formation, nucleus motorius nervi trigemini, cochlear and vestibular area, and nucleus spinalis nerve trigemini. Our results suggest that galanin may have hypophysiotropic and central roles in the turtle Mauremys caspica. © 1994 Wiley-Liss, Inc.     

Immunohistochemical distribution and biological activity of pituitary adenylate cyclase-activating polypeptide (PACAP) in the central nervous system of the frog Rana ridibunda.

The primary structure of frog pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been determined and the results show that the sequence of PACAP has been highly conserved during evolution. In particular, the structure of the 1-27 fragment of PACAP is identical in frog and mammals. Using an antiserum raised against PACAP27, we have investigated the distribution of PACAP-containing neurons in the central nervous system of the frog Rana ridibunda by the immunofluorescence technique. The main populations of immunoreactive perikarya were located in the medial and ventral diencephalon, i.e., the preoptic nucleus, the ventral and dorsal infundibular nuclei, the nucleus posterocentralis thalami, and the ventral and ventrolateral areas of the thalamus. In the telencephalon, sparse cell bodies were found in the nucleus accumbens septi, the amygdala, the pallial commissure, and the bed nucleus of the pallial commissure. In the hindbrain, the torus semicircularis, the nucleus profundus and the nucleus anteroventralis tegmenti of the mesencephalon also contained populations of PACAP-immunoreactive perikarya. Beaded nerve fibers were observed throughout the brain. Occasionally they formed bundles, e.g., from the ventral infundibulum to the external vascular layer of the median eminence, from the central thalamus to the optic tectum, and rostrocaudally, from the nucleus accumbens septi to the nucleus entopeduncularis. Other areas, such as the interpeduncular nucleus, the nucleus isthmi and the roots of cranial nerves V and VIII in the medulla oblongata, were also densely innervated. The adenylate cyclase-stimulating activity of PACAP was tested by using a static incubation technique for hypothalamic slices.(ABSTRACT TRUNCATED AT 250 WORDS)     

Horseradish peroxidase study of tectal afferents in Xenopus laevis with special emphasis on their relationship to the lateral-line system

Afferent projections to the tectum opticum of the clawed toad Xenopus laevis were studied by injections of horseradish peroxidase (HRP) into the tectum. Cells were labelled in the following nuclei, listed from rostral to caudal: nucleus entopeduncularis anterior, nucleus anterior thalami, nucleus posterior thalami, nucleus ventromedialis thalami, nucleus ventrolateralis thalami pars dorsalis, nucleus lateralis thalami pars posterodorsalis, nucleus neuropilis postthalamici, nucleus lentiformis mesencephali, nucleus praetectalis, nucleus laminaris tori semicircularis, nucleus principalis tori semicircularis, nucleus magnocellularis tori semicircularis, nucleus profundus mesencephali, nucleus anterodorsalis tegmenti, nucleus posterodorsalis tegmenti, nucleus posteroventralis tegmenti, nucleus isthmi, nucleus lineae lateralis pars rostralis, nucleus lineae lateralis pars caudalis, nucleus intermedius, nucleus lateralis nervi octavi, nucleus descendens nervi trigemini, nucleus reticularis superior, nucleus reticularis medius, nucleus reticularis inferior, nucleus reticularis lateralis, nucleus cuneatus and area dorsalis medullae spinalis. Four of these nuclei can be associated with lateral-line processing: the nuclei lineae lateralis rostralis and caudalis of the medulla and the centrolateral nuclei magnocellularis and principalis of the torus semicircularis. The toric input is particularly prominent; it is topologically organized in that central parts of the torus project to the medial tectum, and lateral parts of the torus project to the rostrolateral tectum. For comparison, the torotectal connection was also examined in several anuran species that lose their lateral line at metamorphosis. In these animals, this projection is less well developed than in Xenopus. Therefore, it is argued that the torotectal connection primarily conveys lateral-line information.     

Alpha-melanocyte stimulating hormone immunoreactivity in the brain of the cichlid fish Oreochromis mossambicus

This study reports the distribution of a pro-opiomelanocortin-derived neuropeptide α–MSH in the brain of the cichlid fish Oreochromis mossambicus. α–MSH-ir fibres were found in the granule cell layer of the olfactory bulb, the medial olfactory tract, the pallium and the subpallium, whereas in the preoptic area of the telencephalon, few large α–MSH-ir perikarya along with extensively labeled fibres were observed close to the ventricular border. Dense network of α–MSH-ir fibres were seen in the hypothalamic areas such as the nucleus preopticus pars magnocellularis, the nucleus preopticus pars parvocellularis, the suprachiasmatic nucleus, the nucleus anterior tuberis, the paraventricular organ, the subdivisions of the nucleus recessus lateralis and the nucleus recessus posterioris. In the nucleus lateralis pars medialis, some α–MSH-ir perikarya and fibres were found along the ventricular margin. In the diencephalon, numerous α–MSH-ir fibres were detected in the nucleus posterior tuberis, the nucleus of the fasciculus longitudinalis medialis and the nucleus preglomerulosus medialis, whereas in the mesencephalon, α–MSH-ir fibres were located in the optic tectum, the torus semicircularis and the tegmentum. In the rhombencephalon, α–MSH-ir fibres were confined to the medial octavolateralis nucleus and the descending octaval nucleus. In the pituitary gland, densely packed α–MSH-ir cells were observed in the pars intermedia region. The widespread distribution of α–MSH-immunoreactivity throughout the brain and the pituitary gland suggests a role for α–MSH peptide in regulation of several neuroendocrine and sensorimotor functions as well as darkening of pigmentation in the tilapia.     

Connections of the auditory midbrain in a teleost fish, Cyprinus carpio

Central auditory pathways were traced in Japanese carp, Cyprinus carpio, using electrophysiological mapping and HRP tract-tracing methods. Multiunit recordings made from the carp torus semicircularis, the major midbrain area for processing octavolateralis information, revealed a mediolateral segregation of auditory and lateral line sensory modalities. Iontophoretic injections of HRP were made into the medial torus to trace afferent and efferent projections of the carp auditory midbrain. Following unilateral HRP injections into the medial torus, retrogradely labeled neurons were observed within six nuclei of the carp medulla. Two octaval nuclei, the anterior octavus nucleus and descending octavus nucleus, contained HRP-filled neurons. Labeled neurons were also observed within the ipsilateral superior olive, scattered among fibers of both lateral lemnisci, and bilaterally within the medullary reticular formation. In addition, bilateral retrograde cell labeling was found within a group of Purkinje-like cells located adjacent to the IVth ventricle, just rostral to the level of the VIIIth nerve. Few labeled neurons were found within the nucleus medialis, a principal target for lateral line afferents within the medulla. At midbrain levels, retrogradely labeled neurons were observed within the contralateral torus semicircularis and the ipsilateral optic tectum. Three forebrain nuclei project to the carp auditory midbrain. Within the diencephalon, descending projections originate from the anterior tuberal nucleus, bilaterally, and from the ipsilateral central posterior thalamic nucleus. The ipsilateral caudal telencephalon also projects to the carp auditory midbrain via large multipolar neurons within area dorsalis pars centralis. Anterograde labeling of fibers and terminals revealed efferent projections of the carp auditory midbrain to the following targets: the ipsilateral superior olive, the ipsilateral medullary reticular formation, the deep layers of the optic tectum, the contralateral torus semicircularis, the anterior tuberal nucleus, and the central posterior thalamic nucleus. These results, together with recent studies of lateral line pathways in teleosts (Finger, '80, '82a), demonstrate that central auditory and lateral line pathways are anatomically distinct in the carp, at least from medullary to diencephalic levels. Furthermore, there are striking similarities in the organization of the central auditory pathways of the carp and those of amphibians and land vertebrates.     

Distribution of galanin-like immunoreactive elements in the brain of the adult lamprey Lampetra fluviatilis

Galanin is a brain-gut peptide present in the central nervous system of vertebrates and invertebrates. The distribution of galanin-like immunoreactive perikarya and fibers in the brain of the river lamprey Lampetra fluviatilis (Agnatha) has been studied immunocytochemically by using antisera against rat and porcine galanin. Galanin-like immunoreactive perikarya were seen in the telencephalon and mediobasal diencephalon. In the telencephalon, they were present in the nucleus olfactorius anterior, nucleus basalis, and especially, in the nucleus commissurae anterioris. The diencephalon contained most of the immunoreactive neurons. They were located in the nucleus commissurae praeinfundibularis, nucleus ventralis hypothalami, nucleus commissurae postinfundibularis, nucleus ventralis thalami, and nucleus dorsalis thalami pars medius. Most of the galanin-like immunoreactive infundibular neurons showed apical processes contacting the cerebrospinal fluid. Immunoreactive fibers and terminals were widely distributed throughout the neuraxis. In the telencephalon, the richest galaninergic innervation was found in the nucleus olfactorius anterior, lobus subhippocampalis, corpus striatum, and around the nucleus septi and the nucleus praeopticus. In the diencephalon, the highest density of galanin-like immunoreactive fibers was seen in the nucleus commissurae postopticae, nucleus commissurae praeinfundibularis, nucleus ventralis hypothalami, nucleus dorsalis hypothalami, and neurohypophysis. In the mesencephalon and rhombencephalon, the distribution of immunoreactive fibers was heterogeneous, being most pronounced in a region between the nucleus nervi oculomotorii and the nucleus interpeduncularis mesencephali, in the nucleus isthmi, and in the raphe region. A subependymal plexus of immunoreactive fibers was found throughout the ventricular system. The distribution of immunoreactive neurons and fibers was similar to that of teleosts but different to those of other vertebrate groups. The possible hypophysiotropic and neuroregulatory roles of galanin are discussed. © 1996 Wiley-Liss, Inc.     

Afferents of the lamprey optic tectum with special reference to the GABA input: combined tracing and immunohistochemical study

The optic tectum in the lamprey midbrain, homologue of the superior colliculus in mammals, is important for eye movement control and orienting responses. There is, however, only limited information regarding the afferent input to the optic tectum except for that from the eyes. The objective of this study was to define specifically the gamma-aminobutyric acid (GABA)-ergic projections to the optic tectum in the river lamprey (Lampetra fluviatilis) and also to describe the tectal afferent input in general. The origin of afferents to the optic tectum was studied by using the neuronal tracer neurobiotin. Injection of neurobiotin into the optic tectum resulted in retrograde labelling of cell groups in all major subdivisions of the brain. The main areas shown to project to the optic tectum were the following: the caudoventral part of the medial pallium, the area of the ventral thalamus and dorsal thalamus, the nucleus of the posterior commissure, the torus semicircularis, the mesencephalic M5 nucleus of Schober, the mesencephalic reticular area, the ishtmic area, and the octavolateral nuclei. GABAergic projections to the optic tectum were identified by combining neurobiotin tracing and GABA immunohistochemistry. On the basis of these double-labelling experiments, it was shown that the optic tectum receives a GABAergic input from the caudoventral part of the medial pallium, the dorsal and ventral thalamus, the nucleus of M5, and the torus semicircularis. The afferent input to the optic tectum in the lamprey brain is similar to that described for other vertebrate species, which is of particular interest considering its position in phylogeny.     

Distribution of melanin-concentrating hormone-like immunoreactivity in the central nervous system of Rana esculenta

The distribution of salmon and rat melanin-concentrating hormone (MCH)-like and neuropeptide glutamate-isoleucine (NEI)-like immunoreactivity in the brain and spinal cord of the frog Rana esculenta was studied with immunohistochemistry. In the telencephalon, only fibers showed immunoreactivity in the olfactory bulb, lateral pallium, diagonal band, septum, and the amygdala. Immunoreactive fibers were abundant in all diencephalic structures, except the optic tract, the visual neuropils, and the habenula. Several cells in the central thalamic nucleus and a few in the suprachiasmatic nucleus were stained with the MCH antisera. Cells and their processes were intensely stained in the dorsal hypothalamus with the MCH and NEI antisera. Immunoreactive fibers were found in all tegmental nuclei and the white matter of the mesencephalon. They formed terminal plexuses in the deep layers of the optic tectum and the laminar nucleus of the torus semicircularis. Immunoreactive fibers were sparse in the rhombencephalon and the spinal cord.     

Organisation of lateral line and auditory areas in the midbrain of Xenopus laevis

Lateral line areas in the midbrain of Xenopus laevis were identified by recording evoked potentials and neural activity elicited by stimulating anterior and posterior lateral line nerves. Spike activity was found in the lateral half of the optic tectum, ventrolateral tectum, and torus semicircularis. Contra- and ipsilateral lateral line pathways to these regions were identified. Spike discharge was associated with an evoked potential (EP) consisting of a large negative-positive wave sometimes preceded by a small positive-negative deflection. EP depth profiles varied according to electrode position within the lateral line midbrain projection field. In the middle of the field a dramatic increase in EP growth occurred as the electrode passed through the torus semicircularis, with peak amplitudes being achieved 900-1,100 micron from the surface within nucleus principalis and magnocellularis. Tracks at the lateral edge of the field showed a steady growth of EP, with peak amplitudes around 600 micron as the electrode passed through ventrolateral tectum. Auditory responses to tone pips were found in the nucleus laminaris and principalis in caudomedial regions of the torus semicircularis, in areas lying medial to the main centers of lateral line evoked activity; this is a similar organisation to that found in teleost fish. The results indicate the torus semicircularis and deep layers of the lateral tectum to be involved in lateral line processing Some topographic separation of the representation of anterior and posterior lateral line systems is indicated. The possible involvement of these areas in lateral line stimulus localisation is discussed.     

Distribution of monoamine-containing neurons in the brain of a teleost, Carassius auratus (Cyprinidae)

The occurrence and distribution of monoamine-(MA) containing neurons and fibres in the brain of Carassius was investigated by formaldehyde-induced fluorescence (FIF) histochemistry (Falck-Hillarp technique). Many brightly green-fluorescent nerve cell perikarya were found in the nucleus dorsolateralis and ventromedialis, in the nucleus posterioris periventricularis, in the nucleus recessus lateralis and posterioris. They also occurred in the mesencephalic nucleus lateralis valvulae, in the metencephalic nucleus gustatorius secundus and near the ventricular borders of the facial and vagal lobes in the myelencephalon. Many fluorescent fibres and nerve terminals were localized in the frontal and medio-lateral parts of the telencephalon, showing fluorescent connections to the caudal parts. In the diencephalon, MA-fibres branched in a horizontal and ventral tract, leading to the medulla oblongata and the hypothalamic nuclei, respectively. There were laterally situated fibres connecting the hypothalamic nuclei with the medulla and the nucleus gustatorius secundus. Many fluorescent fibres were found in the middle layers of the tectum opticum, in the torus semicircularis, in the lobus inferior and in the medulla oblongata. Considerably fewer fibres occurred in the corpus cerebelli and in the dorsal parts of the hindbrain lobes. These results are compared with the MA-system in the brains of other fish.     

Telencephalic ascending acousticolateral system in a teleost (Sebastiscus marmoratus), with special reference to the fiber connections of the nucleus preglomerulosus

Acousticolateral systems were examined by means of the horseradish peroxidase tracing method in a teleost (Sebastiscus marmoratus). The torus semicircularis projected bilaterally to the optic tectum, nucleus ventromedialis thalami of Schnitzlein ('62), and reticular formation; contralaterally to the torus semicircularis; and ipsilaterally to the nucleus preglomerulosus of Schnitzlein ('62) and the inferior olive. No topographic organization was detected between the torus semicircularis and the nucleus preglomerulosus. Ipsilateral inputs to the torus were from dorsal telencephalic areas (pars centralis, Dc; pars dorsalis, Dd; and the dorsal part of pars medialis, dDm) and the optic tectum. Contralateral inputs to the torus were from the torus semicircularis, a caudal part of the cerebellum, and a portion of the trigeminal complex. The torus also received bilateral input from the nucleus ventromedialis thalami, nucleus of lemniscus lateralis, nucleus medialis, anterior octaval nucleus, descending octaval nucleus, and the reticular formation. Retrogradely labeled cells in the octaval nuclei were seen predominantly subsequent to HRP injections in the medial torus, while cells in the nucleus medialis were retrogradely labeled following injections into the lateral torus. HRP injections into the nucleus preglomerulosus labeled cells in the superficial region of the torus, while injections into the nucleus ventromedialis thalami labeled cells in the deep region. The nucleus preglomerulosus received inputs bilaterally from the nucleus of the lemniscus lateralis and reticular formation and ipsilaterally from the dorsal telencephalic areas (Dc, Dd, and dDm) and the torus semicircularis. In turn the nucleus preglomerulosus projected to Dd and Dm. Fibers arising in the nucleus ventromedialis thalami ended in Dc, Dd, Dm, and area ventralis pars supracommissuralis (Vs). Homology between the nucleus preglomerulosus and the central thalamic nucleus in amphibians, the nucleus reuniens in reptiles, the nucleus ovoidalis in birds, and the medial geniculate body in mammals is discussed.     

Thalamic fiber connections in a teleost (Sebastiscus marmoratus): visual somatosensory, octavolateral, and cerebellar relay region to the telencephalon

Fiber connections of the nucleus ventromedialis thalami (VM) of Schnitzlein (J. Comp. Neurol. 118:225-267, '62) in a teleost (Sebastiscus marmoratus) were examined by means of the horseradish peroxidase (HRP) tracing method. This nucleus receives fibers from the ipsilateral telencephalon (area dorsalis pars centralis), contralateral retina, contralateral VM, ipsilateral optic tectum, ipsilateral torus semicircularis, contralateral corpus cerebelli, contralateral sensory nucleus of the trigeminal nerve, bilateral bulbospinal reticular formation, contralateral obex region, and contralateral dorsal portion of upper spinal segments. In turn, axons arising from VM terminate in the dorsal telencephalic areas (pars centralis, pars dorsalis, and pars medialis) ipsilaterally, ventral telencephalic area (pars supracommissuralis) bilaterally, nucleus prethalamicus of Meader (J. Comp. Neurol. 60:361-407, '34) bilaterally, nucleus dorsomedialis thalami bilaterally, VM contralaterally, optic tectum bilaterally, torus semicircularis bilaterally, and nucleus lateralis valvulae ipsilaterally. Based on the cytoarchitecture and fiber connections, VM is subdivided into rostral and caudal components. The caudal part of VM in Sebastiscus is considered to be a multimodal thalamic complex that contains some cells that constitute the dorsal thalamus in other vertebrate groups.     

Fos Localization in Cytosolic and Nuclear Compartments in Neurones of the Frog, Rana esculenta, Brain: An Analysis Carried Out in Parallel with GnRH Molecular Forms

C-fos activity was determined in the brain of the frog, Rana esculenta, during the annual sexual cycle. The localization of GnRH molecular forms (mammalian- and chicken-GnRHII) was also carried out to determine whether or not the proto-oncogene and the peptides showed a functional relationship. Northern blot analysis of total RNA revealed the presence of a single strong signal of c-fos like mRNA of 1.9 Kb during February and April. This was followed by expression of c-Fos protein (Fos) in several brain areas during March and July shown by immunocytochemistry. In particular, the olfactory region, the lateral and medial pallium, the nucleus lateralis septi, the ventral striatum, the caudal region of the anterior preoptic area, the suprachiasmatic nucleus, the ventral thalamus, tori semicircularis and ependymal layers of the tectum were immunostained. There was no overlap between Fos immunoreactive perikarya and GnRH immunoreactive perikarya (e.g. gonadotrophin-releasing hormone (GnRH) in the rostral part and Fos in the caudal region of the anterior preoptic area). Interestingly, a cytoplasmic localization of Fos was also observed by immunocytochemistry and gel retardation experiments supported this observation. Cytoplasmic extracts from September-October animals bound the AP1 oligonucleotide. The complex was not available in the nuclear extracts from the same preparation, suggesting that, besides Fos, Jun products were also present. Conversely, nuclear but not cytosolic binding was detected in the brain of animals collected in July. In conclusion, we show that Fos and GnRH activity does not correlate in the frog brain and, for the first time in a vertebrate species, we give evidence of a cytoplasmic AP1 complex in neuronal cells.     

Serotonin-immunoreactive neurons in the brain of Eigenmannia lineata (Gymnotiformes, Teleostei).

The distribution of serotonin-immunoreactive (5-HTi) neurons was determined by the peroxidase-antiperoxidase technique. 5-HT-immunoreactive nerve cells (or perikarya) occurred in the diencephalic nucleus ventromedialis (nvm), in the so-called pre-pacemaker nucleus (ppm), in a laterally located (unnamed) nucleus (G1), in the nucleus posterior periventricularis (nppv), the nucleus recessus lateralis (nrl) and the nucleus recessus posterior (nrp). 5-HT-immunoreactivity could be localized in the pars intermedia and the proximal pars distalis of the pituitary gland. Large 5-HTi perikarya were found in the lamina VI of the mesencephalic torus semicircularis (ts). Intensely immunostained 5-HTi perikarya occurred in the raphe region. 5-HT-immunoreactivity was also located in the medullary pacemaker nucleus of the specialized electric organ (pm). Only a few 5-HTi fibres were observed in the telencephalon. Ventral to the 3rd ventricle of the diencephalon between the caudal hypothalamic nuclei most of these were fibre bundles dorsal to the nuc. recessus lateralis. Some 5-HTi fibres traversed the pituitary stalk to the proximal pars distalis of the pituitary gland. Scattered 5-HTi fibres were seen in the torus semicircularis, lobus inferior (li) and cerebellum, while more fibres appeared in the medulla oblongata (mo) and below the pacemaker nucleus. The results are compared to those in other fish.     

Localization of neurons afferent to the optic tectum in longnose gars

Afferent pathways to the optic tectum in the longnose gar were determined by unilateral tectal injections of HRP. Retrogradely labeled cells were observed in the ipsilateral caudal portion of the rostral entopeduncular nucleus and bilaterally in the rostral half of the lateral zone of area dorsalis of the telencephalon. The following diencephalic cell groups were also labeled following tectal injections: the ipsilateral anterior, ventrolateral, and ventromedial thalamic nuclei, the periventricular pretectal nucleus, and the central pretectal nucleus (bilaterally); the ventromedial thalamic and central pretectal nuclei revealed the largest number of labeled cells. At midbrain levels, retrogradely labeled cells were seen in the ipsilateral torus longitudinalis, nucleus isthmi, and accessory optic nucleus; cells were labeled bilaterally in the torus semicircularis and a rostral tegmental nucleus. Only a few cells were labeled in the contralateral optic tectum, suggesting that few of the fibers of the intertectal commissure are actually commissural to the tectum. At hindbrain levels, retrogradely labeled cells were seen bilaterally in the locus coeruleus, the superior, medial, and inferior reticular formations, the eurydendroid cells of the cerebellum, and the nucleus of the descending trigeminal tract; the contralateral dorsal funicular nucleus also exhibited labeling. Clearly, the tectum in gars receives a substantial number of nonvisual afferents from all major brain areas, most of which have been reported in other vertebrates. The functional significance of these afferent sources and their probable homologues in other vertebrate groups are discussed.