Periventricular and central nuclei of the pretectal area of diencephalon of the sturgeons

Cytoarchitectonics of periventricular and central nuclei of the pretectal area was studied in four species of the sturgeons: the great sturgeon Huso huso, L., the Russian sturgeon Acipenser gъldenst?dti persicus n. kurensis, Belyaeff, the starred sturgeon Ac. stellatus, Pall., and the barbel sturgeon Ac. nudiventris, Lov.; this pretectum part has a similar structure. Study of these parts of the pretectal area was carried out by methods of Nissl and Bielshowskii modified by Viktorov. In this part of the pretectal area, nine nuclear structures were described, eight of them—nuclear; these are ventral periventricular pretectal nucleus and its dorsal component, dorsal periventricular pretectal nucleus, nucleus of medial longitudinal bundle, subcomissural organ, medial and lateral intercalate nuclei, and central and posterior pretectal nuclei. The main attention has been paid to the issue of the evolutional progression of this part of the pretectal area in the sturgeons as compared with other Actinopterygii.     

Periventircular and central nuclei of the diencephalon pretectal area of the sturgeons

Cytoarchitectonics of periventricular and central nuclei of the pretectal area was studied in four species of the sturgeons: the great sturgeon Huso huso, L., the Russian sturgeon Acipenser güldenst?dti persicus n. kurensis, Belyaeff, the starred sturgeon Ac. stellatus, Pall., and the barbel sturgeon Ac. nudiventris, Lov.; this pretectum part has a similar structure. Study of these parts of the pretectal area was carried out by methods of Nissl and Bielshowskii modified by Viktorov. In this part of the pretectal area, nine nuclear structures were described, eight of them--nuclear; these are ventral periventricular pretectal nucleus and its dorsal component, dorsal periventricular pretectal nucleus, nucleus of medial longitudinal bundle, subcomissural organ, medial and lateral intercalate nuclei, and central and posterior pretectal nuclei. The main attention has been paid to the issue of the evolutional progression of this part of the pretectal area in the sturgeons as compared with other Actinopterygii.     

Organization of diencephalon of the sturgeons. Posterior tubercular area. Caudal region

Cytoarchitectonics of caudal region of the posterior tubercular area of diencephalon was studied in four species of the true sturgeons: the giant sturgeon, Huso huso L., Kura sturgeon, Acipenser güldenstädtii persicus n. Kurensis Belyaeff, stellate sturgeon, Ac. stellatus Pall. and the barbel sturgeon Ac. nudiventris Lov. Morphologic organization of the brain region was studied by using staining techniques of Nissl and Bielschowski (Viktorov’s modification). Five nuclei were identified in the caudal region of the posterior tubercular area in all studied species: caudomedial, caudal and lateral thalamic nuclei forming the medial group, as well as lateral torus and posterior thalamic nuclei forming the lateral group. The latter two nuclei have their subdivisions. Characteristic peculiarity of the caudal region is the presence of only migrated nuclei. It is concluded that the level of differentiation of the diencephalon posterior tubercular area of the sturgeons allows considering it as one of the most evolutionary advanced structures among those in the actinopterygian fish line.     

Organization of hypothalamic area of diencephalon in the sturgeons

Cytoarchitectonics of hypothalamic area of diencephalon of the sturgeons was studied in serial sections by techniques of Nissl staining and Bielschowski impregnation in Viktorov’s modification. The hypothalamus was shown to be the most expanded area of diencephalon and forms its the most ventral part. The hypothalamic area of four studied sturgeons, the hausen, Huso huso L., Kura sturgeon, Acipenser guldenstaedtii persicus n. Kurensis Belyaeff, Caspian sturgeon, Ac. stellatus Pall. and the barbel sturgeon Ac. nudioventris Lov. was found to have similar structure. Eleven nerve structures are identified and described in the hypothalamic area: dorsal, ventral, and caudal periventricular zones, rostral and dorsal hypothalamic nuclei, ventral and ventrolateral hypothalamic nuclei, diffuse and central nuclei of the inferior lobes, nucleus of the vascular sac, and mammillary nucleus. Peculiarities and common features of organization of four major parts of hypothalamus of the sturgeons are considered in comparison with those of other ray-finned fish. The performed analysis indicates a high level of development of hypothalamus of the sturgeons.     

Cytoarchitectonic pattern of the hypothalamus in the turtle,Lissemys punctata granosa

Summary In the hypothalamus of the turtle, Lissemys punctata granosa, two magnocellular and 23 parvocellular neuronal complexes can be distinguished. The magnocellular complexes include the nucleus supraopticus and the nucleus paraventricularis; paraventricular neurons are partly arranged in rows parallel to the third ventricle. Most infundibular parvocellular nuclei display neurons disposed in rows parallel to the ventricular surface. In the preoptic region, the prominent parvocellular neuronal complexes encompass the nucleus periventricularis anterior, lateral preoptic area, the nucleus of the anterior commissure and the nucleus suprachiasmaticus. The prominent nucleus periventricularis posterior extends caudad and shows neurons arranged in vertical rows parallel to the third ventricle. Other parvocellular nuclei of the rostral hypothalamus are composed of clustered subunits. The nucleus arcuatus is a fairly large nuclear entity extending from the level marked dorsally by the nucleus paraventricularis to the area occupied by the nucleus of the paraventricular organ. A well-developed ventromedial nucleus is located ventrolateral to the paraventricular organ. The prominent paraventricular organ consists of tightly arranged neurons, some of which possess apical projections into the third ventricle; it is surrounded by the nucleus of the paraventricular organ. Nucleus hypothalamicus medialis et lateralis, nucleus hypothalamicus posterior and the nuclei recessus infundibuli are further nuclear units of the tuberal region. The caudal end of the hypothalamus is marked by the nucleus mamillaris; its neurons are scattered among the fibers of the retroinfundibular commissure. The median eminence is well developed and shows a large medial and two lateral protrusions into the infundibular recess.     

Organization of diencephalon of the sturgeons. Preoptic area

Cytoarchitectonics of preoptic area of diencephalon of chondroid ganoid fish (the sturgeons) was studied in serial sections using Nissl and Bilschowski techniques, the latter in Viktorov’s modification). The preoptic area of the hausen, Huso huso L., Kura sturgeon, Acipenser guldenstaedtii persicus n. kurensis Belyaeff, Caspian sturgeon, Acipenser stellatus Pall. and the sturgeon Acipenser nudioventris Lov. was shown to be one of the largest parts of diencephalon. It is located along the rostral excess of the third ventricle and the anterior third of the ventricle thalamic part. Eight nuclei are identified in the preoptic area: (1) anterior microcellular preoptic nucleus, (2) suprachiasmatic nucleus, (3) accessory preoptic nucleus, (4) intrachiasmatic nucleus, (5) magnocellular preoptic nucleus, (6) posterior microcellular preoptic nucleus, (7) caudal preoptic nucleus, (8) entopeduncular nucleus. Besides, microcellular, magnocellular, and gigantocellular parts are identified in the magnocellular preoptic nucleus. The obtained results indicate high differentiation of this area of the sturgeons among Actinopterygii.     

Immunohistochemical mapping of galanin-like neurons in the rat central nervous system

Using an antiserum generated in rabbits against synthetic galanin (GA) and the indirect immunofluorescence method, the distribution of GA-like immunoreactive cell bodies and nerve fibers was studied in the rat central nervous system (CNS) and a detailed stereotaxic atlas of GA-like neurons was prepared. GA-like immunoreactivity was widely distributed in the rat CNS. Appreciable numbers of GA-positive cell bodies were observed in the rostral cingulate and medial prefrontal cortex, the nucleus interstitialis striae terminalis, the caudate, medial preoptic, preoptic periventricular, and preoptic suprachiasmatic nuclei, the medial forebrain bundle, the supraoptic, the hypothalamic periventricular, the paraventricular, the arcuate, dorsomedial, perifornical, thalamic periventricular, anterior dorsal and lateral thalamic nuclei, medial and central amygdaloid nuclei, dorsal and ventral premamillary nuclei, at the base of the hypothalamus, in the central gray matter, the hippocampus, the dorsal and caudoventral raphe nuclei, the interpeduncular nucleus, the locus coeruleus, ventral parabrachial, solitarii and commissuralis nuclei, in the A1, C1 and A4 catechaolamine areas, the posterior area postrema and the trigeminal and dorsal root ganglia. Fibers were generally seen where cell bodies were observed. Very dense fiber bundles were noted in the septohypothalamic tract, the preoptic area, in the hypothalamus, the habenula and the thalamic periventricular nucleus, in the ventral hippocampus, parts of the reticular formation, in the locus coeruleus, the dorsal parabrachial area, the nucleus and tract of the spinal trigeminal area and the substantia gelatinosa, the superficial layers of the spinal cord and the posterior lobe of the pituitary. The localization of the GA-like immunoreactivity in the locus coeruleus suggests a partial coexistence with catecholaminergic neurons as well as a possible involvement of the GA-like peptide in a neuroregulatory role.     

The hypothalamus of Lacerta sicula R.

Summary The posterior (caudal) hypothalamus of the lizard, Lacerta sicula R. was investigated by means of Golgi methods. The periventricular grey is formed mainly by isodendritic bipolar and multipolar neurons, while in the lateral hypothalamus a more stellate form of neuronal elements is encountered. CSF-contacting neurons are restricted to the tuberal area and to the paraventricular organ. In the latter area they are highly differentiated and endowed with laterally branched processes. The overall pattern of the lizard hypothalamus (organization of neuropil, lateral nuclei, appearance of cell clusters, morphology of the neuronal elements) represents an intermediate stage in the phylogenetic development of the hypothalamus, being more advanced than the amphibian stage.     

Organization of diencephalon of the sturgeons. External nuclei of the pretectal area

Cytoarchitectonics of the external nuclei of the pretectal area was studied in four species of the sturgeons: great sturgeon, Huso huso L., Kura sturgeon, Acipenser gueldenstaedtii persicus n. Kurensis Belyaeff, stellate sturgeon, Ac. stellatus Pall. and barbel sturgeon, Ac. nudiventris Lov. Study of morphological organization of the structures was carried out using routine Nissl staining and Bilschowski impregnation technique in Viktorov’s modification. Similar structure of this pretectal area was found in the species. Five nuclear formations were described in this pretectal area: parvocellular and magnocellular external pretectal nuclei, laminiform nucleus of pretectum, dorsal pretectal nucleus, and the accessory optic nucleus. Comparison of the obtained data with the literature revealed a high level of differentiation of the area of pretectum in the sturgeons. Also, a general conclusion is given on the organization of the whole pretectal area in the sturgeons.     

Organization of diencephalon of the sturgeons. Dorsothalamic and epithalamic areas

Cytoarchitectonics of the dorsal part of diencephalon and epithalamus was studied in four species of the true sturgeons: the great sturgeon Huso huso L., the Kura sturgeon Acipenser gƅlden-st∂dtii persicus n. Kurensis Belyaeff, the starred sturgeon Ac. stellatus Pall., and the barbel sturgeon Ac. nudiventris Lov. Material was processed using routine Nissl and Bielschowski staining techniques (the latter in Viktorov’s modification). The described areas are the smallest among diencephalic regions. Dorsal thalamus is exceeded by the ventral one both in length and in the number nuclear structures. It includes four nuclear structures, three of which are periventricular: the anterior, posterior dorsal, and central nuclei, while the subhabenular nucleus is a migrated one. Epithalamic area has a pronounced right-left asymmetry that consists both in the external appearance of these structures and in their internal organization. Three types of neurons were revealed in epithalamic structures: granular cells, rounded neurons with poorly expressed processes, and bipolar neurons with clearly seen processes. In the epithalamic area, a sufficiently large nervous structure designated as the central habenular nucleus consisting of relatively large rounded neurons was described. A conclusion is made about a unique organization the studied areas in the true sturgeons, which distinguishes them markedly among both other actinopterygian fish and the higher organized vertebrates.     

Organization of the diencephalon ventrothalamic area in the sturgeons

Cytoarchitectonics of ventrothalamic area of the diencephalon of the sturgeons was studied in four species of the sturgeons, the great sturgeon Huso huso L., the Kura sturgeon Acipenser guelden-staedtii persicus n. Kurensis Belyaeff, the Caspian sturgeon, Ac. stellatus Pall., and the barbel sturgeon Ac. nudioventris Lov. using Nissl staining and Bilschowski impregnation techniques in Viktorov’s modification. The ventral thalamus of the sturgeons was found to include seven nuclei: ventromedial, ventrolateral, intermediate and ventral thalamic nuclei, thalamic eminence, and nuclei of ventral and medial optic tracts. The main attention was paid to comparative analysis of this area in the sturgeons and other actinopterygian fish. The structures common to all ray-finned fish or only to the lower teleosts and ganoids as well as characterizing only the sturgeons.     

Distribution of pro-opiomelanocortin and its peptide end products in the brain and hypophysis of the aquatic toad, Xenopus laevis

Using in situ hybridization with a pro-opiomelanocortin (POMC)-mRNA probe and immunocytochemistry with antisera to POMC and to various POMC-derived peptides, it is shown that melanotrope cells in the pars intermedia of the hypophysis of the South African aquatic toad Xenopus laevis contain POMC, α-melanophore-stimulating hormone (α-MSH), γ-MSH, acetylated and non-acetylated endorphins and adrenocorticotropic hormone (ACTH). With the exception of γ-MSH, these peptides are also found in the corticotrope cells in the rostral pars distalis. In the Xenopus brain, neuronal cell bodies in the ventral hypothalamic nucleus express POMC, α-MSH, γ-MSH, non-acetylated endorphins and ACTH, neurones in the anterior preoptic area reveal POMC, α-MSH, γ-MSH and non-acetylated endorphin, neurones in the suprachiasmatic nucleus contain α-MSH, non-acetylated endorphin and ACTH and neurones in the posterior tubercle show α-MSH, non-acetylated endorphin and ACTH immunoreactivities. In the locus coeruleus POMC and ACTH coexist, whereas α-MSH and non-acetylated endorphin occur together in the nucleus accumbens, the striatum and the nucleus of the paraventricular organ. Finally, α-MSH alone is present in the olfactory bulb, the medial septum, the medial and lateral parts of the amygdala, the ventromedial and posterior thalamic nuclei, the optic tectum and the anteroventral tegmental nucleus, and non-acetylated endorphin alone appears in the epiphysis. It is suggested that neurones that form POMC-derived peptides may play a direct or indirect role in the control of POMC-producing hypophyseal cells and/or in the physiological processes these endocrine cells regulate. This idea is supported by the fact that the suprachiasmatic nucleus and the locus coeruleus, both involved in melanotrope cell control, show POMC and POMC-peptide expression. A possible involvement in melanotrope and/or corticotrope control of the anterior preoptic and ventral hypothalamic nuclei, which both express POMC and various POMC-derived peptides, deserves future attention.     

Evidence for the presence of nerve growth factor (NGF) and NGF receptors in human testis

Summary The co-localization of arginine vasopressin-and enkephalin-like immunoreactivities in nerve cells of the rat paraventricular hypothalamic nucleus and adjacent areas was investigated by the simultaneous application of immuno--galactosidase staining and the peroxidase-antiperoxidase method to sections. Arginine vasopressin-like immunoreactive cells were stained blue with immuno--galactosidase staining and enkephalin-like immunoreactive cells brown with the peroxidase-antiperoxidase method. Double-labeled cells with overlap of blue and brown immunoreaction products were identified in the anterior, medial, and lateral parvocellular parts of the paraventricular hypothalamic nucleus as well as in the previously indicated posterior magnocellular part. Other regions that contained double-labeled cells were the lateral hypothalamic area, anterior hypothalamic nucleus, area between the lateral hypothalamic area and anterior hypothalamic nucleus, suprachiasmatic nucleus, and bed nucleus of the stria terminalis, medial division, posterolateral part. These findings suggest that nerve cells with both arginine vasopressin- and enkephalin-like immunoreactivities may be more actively involved in neuroendocrine regulation and neural transmission than previously considered. They may provide a morphological basis for an increase in enkephalin-like immunoreactivity within the anterior pituitary in cases of hemorrhagic shock which is presumably accompanied by arginine vasopressin hypersecretion.Abbreviations AH anterior hypothalamic nucleus - ap anterior parvocellular part of the paraventricular hypothalamic nucleus - BSTMPL bed nucleus of the stria terminalis, medial division, posterolateral part - dp dorsal parvocellular part of the paraventricular hypothalamic nucleus - f fornix - LH lateral hypothalamic area - lp lateral paryocellular part of the paraventricular hypothalamic nuclcus - mp medial parvocellular part of the paraventricular hypothalamic nucleus - MPA medial preoptic area - pm posterior magnocellular part of the paraventricular hypothalamic nucleus - pv periventricular part of the paraventricular hypothalamic nucleus - SC suprachiasmatic nucleus - Zi zona incerta     

Distribution of FMRFamide-like immunoreactivity in the forebrain of the catfish, Clarias batrachus (Linn.).

The anatomical distribution of FMRFamide-like immunoreactivity in the forebrain and pituitary of the catfish, Clarias batrachus, was investigated. Immunoreactive cells were observed in the ganglion cells of the nervus terminalis (NT) and in the medial olfactory tracts. In the preoptic area, FMRFamide-containing perikarya were restricted to the lateral preoptic area, paraventricular subdivision of the nucleus preopticus, nucleus suprachiasmaticus and nucleus preopticus periventricularis posterior. In the postoptic area, some cells of the nucleus postopticus lateralis and nucleus of the horizontal commissure showed moderate immunoreactivity. In the tuberal area, immunoreactivity was observed in few cells of the nucleus hypothalamicus ventralis and nucleus arcuatus hypothalamicus (NAH). Nucleus ventromedialis thalami was the only thalamic nucleus with FMRFamide immunoreactivity. Immunoreactive processes were traceable from the NT through the medial as well as lateral olfactory tracts into the telencephalon and the area ventralis telencephali pars supracommissuralis (Vs). Further caudally, the immunoreactive fibers could be traced into discrete areas, including habenular and posterior commissures, neurohypophysis and pituitary; isolated fibers were also observed in the pineal stalk. A loose network of immunoreactive processes was observed in the olfactory bulbs and the entire telencephalon, with higher densities in some areas, including Vs. A dense plexus of immunoreactive fibers was seen in the pre- and postoptic areas and around the paraventricular organ, while relatively few were observed in the thalamus. A high concentration of fiber terminals was found in the caudal tuberal area.     

Distribution of oxytocin and vasopressin neurons in the diencephalon of the Japanese horseshoe bat, Rhinolophus ferrumequinum. An immunohistochemical study.

The distribution of oxytocin (OXT) and vasopressin (VP) neurons in the diencephalon of the hibernating Japanese horseshoe bat, Rhinolophus ferrumequinum, was immunohistochemically investigated by the avidin-biotin complex method. Magnocellular OXT and VP neurons were localized mainly in the paraventricular nucleus and the supraoptic nucleus. In addition to these main nuclei, both kinds of magnocellular neurons were also found in the periventricular nucleus, perifornical area and lateral hypothalamic area. Extensively distributed parvocellular neurons containing only VP were observed in the rostral and middle portions of the suprachiasmatic nucleus. The size of OXT and VP magnocellular neurons was almost equal in the paraventricular and ventromedial supraoptic nuclei, whereas VP neurons were significantly larger than OXT neurons in the dorsolateral supraoptic nucleus. The OXT and VP cells in the ventral supraoptic nucleus showed a distinctive elliptical shape. Both OXT and VP fibers were distributed in the lateral habenular nucleus, stria medullaris thalami, lateral preoptic area, stria terminalis, and medial and supracapsular part of the bed nucleus of the stria terminalis. Moreover, OXT fibers were found in the substantia nigra, and VP fibers were noted in the nucleus reunions and the paraventricular nucleus of the thalamus.     

Immunocytochemical study of the hypothalamic magnocellular neurosecretory nuclei of the snake Natrix maura and the turtle Mauremys caspica

Summary An immunocytochemical study of the magnocellular neurosecretory nuclei was performed in the snake Natrix maura and the turtle Mauremys caspica by use of antisera against: (1) a mixture of both bovine neurophysins, (2) bovine oxytocin-neurophysin, (3) arginine vasotocin, and (4) mesotocin. Arginine vasotocin- and mesotocin-immunoreactivities were localized in individual neurons of the supraoptic and paraventricular nuclei, with a distinct pattern of distribution in both species. The same cells appeared to be stained by the anti-oxytocin-neurophysin and anti-mesotocin sera. The supraoptic nucleus can be subdivided into rostral medial and caudal portions. In N. maura, but not in M. caspica, neurophysin-immunoreactive neurons were found in the retrochiasmatic nucleus. No immunoreactive elements were seen in the suprachiasmatic nucleus of both species after the use of any of the antisera. A dorsolateral aggregation of neurophysin-containing cells, localized over the lateral forebrain bundle, was present in both species. Magnocellular and parvocellular neurophysin-immunoreactive neurons were present in the paraventricular nucleus of both species. In the turtle, the paraventricular neurons were arranged into four distinct layers parallel to the ependyma; these neurons were bipolar with the major axis perpendicular to the ventricle, and many of them projected processes toward the cerebrospinal-fluid compartment. In N. maura a group of large neurons of the paraventricular nucleus was found in a very lateral position. The posterior lobe of the hypophysis and the external zone of the median eminence contained arginine vasotocin- and mesotocin-immunoreactive nerve fibers. The lamina terminalis of both species was supplied with a dense bundle of fibers containing immunoreactive neurophysin. Neurophysin-immunore-active fibers were also present in the septum, some telencephalic regions, including the cortex and the olfactory tubercule, in the paraventricular organ, and the periventricular and periaqueductal gray of the brainstem.This work was partially supported by a Grant S-85-39 from the Direccion de Investigaciones, Universidad Austral de Chile to E.M. Rodriguez     

Cytoarchitectonic pattern of the hypothalamus in the crocodile,Gavialis gangeticus

Summary The hypothalamus of the crocodile, Gavialis gangeticus, was investigated to reveal the organization of various nuclear complexes and to suggest homologies. The hypothalamic nuclei of G. gangeticus are composed of magnocellular and parvocellular neuronal entities. In the magnocellular system the nucleus supraopticus is well developed, whereas the nucleus paraventricularis and nucleus retrochiasmaticus are represented by scattered somata. Application of cytoarchitectonic criteria permits the delineation of 24 distinct parvocellular nuclear complexes extending rostrocaudally from the anterior commissure to the level indicated by the median eminence and nucleus mamillaris; some are further divisible into subgroups. The nucleus of the preoptic recess appears to be a unique property of the crocodilian hypothalamus. The nucleus suprachiasmaticus possesses a wing-like ventrolateral expansion that protrudes along the lateral aspect of the optic nerve. The tuberal region displays an elaborate pattern of nuclei segregated by regional specializations of the neuropil. The nucleus hypothalamicus posterior occupies the periventricular zone, flanked laterally by the nucleus hypothalamicus dorsomedialis and nucleus arcuatus. Further laterally, extended subdivisions of the nucleus hypothalamicus lateralis contain neurons rich in Nissl substance; the specializations shown by these subdivisions, in comparison to the lateral cell groups in lizards and snakes, are suggestive of enhanced integrative functions. The conspicuous paraventricular organ is encircled by dorsal and ventral divisions of the nucleus of the paraventricular organ. The neurons of the nucleus subfornicalis and nucleus hypothalamicus medialis are few in number, but large in size. The general organization of the hypothalamus of G. gangeticus reveals a mosaic-like pattern with the constituent groups appearing as clusters of small and large neurons, arranged medially and laterally in a definitive manner and accompanied by extensive zones of neuropil in the subependymal and lateral zones of the hypothalamus. The median eminence is divisible into an anterior and a posterior region. The nuclear pattern in the crocodilian hypothalamus reveals a higher state of morphologic organization compared to the situation in lizards or snakes, and thus reflects an evolutionary trend in the avian direction.     

大鼠下丘脑内一氧化氮合酶阳性神经元的分布

用ＮＡＤＰＨ－ｄ组织化学方法观察了大白鼠下丘脑内一氧化氮合酶（ＮＤＳ）阳性神经元的分布及形态特征。结果显示：在视上核、室旁核的大细胞部、环状核、穹窿周核、下丘脑外侧区、下丘脑腹内侧核、下丘脑背内侧核、乳头体区大部分核团均可见一氧化氮合酶阳性神经元聚集成团。在视前内侧区、视前外侧区、下丘脑前区、下丘脑背侧区、下丘脑后区、室周核、室旁核小细胞部及穹窿内可见散在的一氧化氮合酶阳性神经元。室周核内可见呈阳性反应的接触脑脊液神经元的胞体及突起。一氧化氮合酶阳性神经元大多可见突起,有的突起上可见１～２级分支,并可见膨体。下丘脑大部分区域内可见阳性神经纤维。弓状核内可见许多弧形纤维连于第三脑室室管膜和正中隆起。     

Scanning and transmission electron microscopy of intraventricular dendrite terminals of hypothalamic cerebrospinal fluid contacting neurons in Triturus vulgaris

A scanning (SEM) and transmission electron microscopic (TEM) study of the ventricular wall of the hypothalamus of Triturus vulgaris was performed with special regard to the intraventricular dendrite terminals of the cerebrospinal fluid (CSF) contacting neurons of the preoptic area (magnocellular and parvocellular preoptic nuclei), the infundibular lobe (anterior periventricular nucleus, infundibular nucleus), and the paraventricular organ. In the preoptic area and infundibular lobe, the terminals were knob-like or club-shaped, of various sizes (diameter about 0,5 to 3,0 micrometer) and located immediately above the ependyma. Ultrastructurally, they may contain dense-core vesicles of varying sizes. The CSF contacting dendrite endings of the paraventricular organ built up a supraependymal labyrinthic layer which could be divided into a rostral crest-like part and a caudal flat and broad division. In both parts, three main types of terminals of various size and shape could be distinguished: a) ramifying, b) elongated, and c) bulb-like dendrite endings which also differed by their TEM structure. The bulk-like terminals, first of all the small ones, originated from the distal part of the nucleus of the organ (nucleus organi paraventricularis) while the other two types took their origin from its intra- and subependymal part. In all areas investigated, each intraventricular dendrite ending gave rise to a solitary cilium (type 9 X 2 + 0). It differed from the ependymal kinocilia by both SEM and TEM characteristics. In the paraventricular organ, the neuronal cilia were hidden inside, or below the supraependymal layer of terminals. There were intraventricular axons which formed synapses on CSF contacting dendrite endings of both parts of the paraventricular organ. Free intraventricular neurons, further ependymal areas heavily or scarcely ciliated, were described. The CSF contacting dendrite terminals were predominantly present near ventricular recesses and in regions where the ependyma was scarcely ciliated.     

Pattern of afferents to the lateral septum in the guinea pig

Summary The septal region represents an important telencephalic center integrating neuronal activity of cortical areas with autonomous processes. To support the functional analysis of this brain area in the guinea pig, the afferent connections to the lateral septal nucleus were investigated by the use of iontophoretically applied horseradish peroxidase (HRP). Retrogradely labeled perikarya were located in telencephalic, diencephalic, mesencephalic and metencephalic sites. The subnuclei of the lateral septum (pars dorsalis, intermedia, ventralis, posterior) receive afferents from the (i) medial septal nucleus, diagonal band of Broca (pars horizontalis and pars ventralis), and the principal nucleus of the stria terminalis, the hippocampus, and amygdala (nucleus medialis); (ii) the medial habenular nucleus, and the para- (peri-) ventricular, parataenial and reuniens nuclei of the thalamus; the anterior, lateral and posterior hypothalamic areas in particular, the medial and lateral preoptic, suprachiasmatic, periventricular, paraventricular, arcuate, premammillary, and supramammillary nuclei; (iii) the periaquaeductal grey, ventral tegmental area, nucleus interfascicularis, nucleus reticularis linearis, central linear nucleus, interpeduncular nucleus; (iv) dorsal and medial raphe complex, and locus coeruleus. Each subnucleus of the lateral septum displays an individual, differing pattern of afferents from the above-described regions. Based on a double-labeling method, the vasopressinergic and serotonergic afferents to the lateral septum were found to originate in the nucleus paraventricularis hypothalami and the raphe nuclei, respectively.Abbreviations ARC arcuate nucleus - BNST bed nucleus of the stria terminalis - CL central linear nucleus - DBBh diagonal band of Broca (pars horizontalis) - DBBv diagonal band of Broca (pars ventralis) - DR dorsal raphe nucleus - HC hippocampus - IF interfascicular nucleus - IP interpeduncular nucleus - LC locus coeruleus - LDT laterodorsal tegmental nucleus - LHA lateral hypothalamic area - LPO lateral preoptic area - LSN lateral septal nucleus - MA medial amygdaloid nucleus - MH medial habenular nucleus - MPO medial preoptic region - MR medial raphe nucleus - MSN medial septal nucleus - PAG periaquaeductal grey - PEN periventricular nucleus - PHA posterior hypothalamic area - PMd premammillary region (pars dorsalis) - PMv premammillary region (pars ventralis) - PT parataenial nucleus - PVN paraventricular hypothalamic nucleus - PVT paraventricular thalamic nucleus - RE nucl. reuniens - RL nucl. reticularis linearis - SCN suprachiasmatic nucleus - SMl supramammillary region (pars lateralis) - SMm supramammillary region (pars medialis) - SUB subiculum - TS triangular septal nucleus - VTA ventral tegmental area - ac anterior commissure - bc brachium conjunctivum - bp brachium pontis - cc corpus callosum - fr fasciculus retroflexus - fx fornix - ml medial lemniscus - mlf fasciculus longitudinalis medialis - mp mammillary peduncle - mt mammillary tract - oc optic chiasm - on optic nerve - pc posterior commissure - pt pyramidal tract - sm stria medullaris - st stria terminalis - vhc ventral hippocampal commissure Supported by the Deutsche Forschungsgemeinschaft (Nu 36/2-1)