Golgi-like immunoperoxidase staining of hypothalamic magnocellular neurons that contain vasopressin, oxytocin or neurophysin in the rat

Synaptic contacts of ventral striatal cells in the olfactory tubercle of the rat: correlated light and electron microscopy of anterogradely transported Phaseolus vulgaris-leucoagglutinin

Iontophoretic injections of the plant lectin Phaseolus vulgaris-leucoagglutinin (PHA-L) into the dense cell layer of the rat olfactory tubercle (OT) resulted in transport of the substance to the polymorph layer of the OT. Light microscopy revealed that the lectin was taken up in the superficial OT exclusively by medium-sized neurons with spiny dendrites of which the majority extended into the molecular layer. PHA-L-immunoreactive elements were observed in the adjoining part of the polymorph layer in the form of filaments and puncta which the electron microscope revealed to be axons and boutons forming symmetrical synaptic contacts, almost exclusively with typical pallidal-type dendrite profiles. The results reinforce the concept that the medium-size cells of the dense cell layer of the OT represent the ventral-most part of the striatum.

Mapping of transmitter-specific connections: simultaneous demonstration of anterograde degeneration and changes in the immunostaining pattern induced by lesions

This paper describes simple procedures which allow immunohistochemistry to be combined with a newly developed silver degeneration technique for the purpose of mapping transmitter-specific connections on the light microscopic level. Conditions of fixation, survival time and immunohistochemistry that contribute to optimal results are discussed.

Lesions of the tissue surrounding the preoptic recess (AV3V region) affect neurosecretory cells in the paraventricular nuclei in the rat

Lesions of the tissue surrounding the preoptic recess (AV3V region) have severe effects on body fluid homeostasis; these include acute adipsia and failure of the antidiuretic response. Because neurosecretory cells in supraoptic nuclei comprise the major source of antidiuretic hormone (ADH) in this species, we have previously observed the fine structure of supraoptic nuclei in rats with AV3V lesions. Paraventricular nuclei are the other major source of ADH in rats. Therefore, in this investigation we compared the fine structure of paraventricular nuclei in rats which had received AV3V lesions 3 days earlier with that of control rats which had received sham lesions and either had drinking water available or had water withheld for 3 days. Degenerating axons and axon terminals were present in paraventricular nuclei of lesioned rats. The degenerating terminals were in axodendritic and less often in axosomatic synapses. Morphometric evaluation revealed that neurosecretory cells did respond to the dehydrated state of the adipsic-lesioned animals, but the response was significantly attenuated compared to that which occurred in sham-lesioned rats deprived of water for 3 days. It appears that AV3V lesions damage afferent connections and impair the response of neurosecretory cells to dehydration in paraventricular as well as supraoptic nuclei. However, in paraventricular nuclei the response is not completely prevented by AV3V lesions during the adipsic period as was observed in supraoptic nuclei. The presence of a response in paraventricular nuclei may be at least partially stimulated by reduced body fluid volume. Information from volume receptors would be carried from the medulla to paraventricular nuclei by ascending pathways which are not affected by AV3V lesions.

Vasopressin- and neurophysin-immunoreactive neurons in the septal region, medial amygdala and locus coeruleus in colchicine-treated rats

The distribution and morphology of neurons containing vasopressin, oxytocin and their associated neurophysins were examined immunohistochemically in rats given intracerebroventricular injections of colchicine. Under these conditions, numerous neurons containing vasopressin and neurophysin were found in several brain areas in addition to those previously described in the hypothalamus. Individual parvocellular vasopressin neurons were scattered in the medial and lateral septum and vertical limb of the nucleus of the diagonal band, while a large number of such neurons were found throughout both the bed nucleus of the stria terminals and the dorsal portion of the medial amygdala. In addition a small cluster of parvocellular vasopressin neurons was present adjacent to the top of the third ventricle in the posterior dorsal hypothalamic area and a number of such neurons were found in the ventral locus coeruleus and sub coeruleus. The mean diameters of these parvocellular vasopressin neurons ranged from 16.6 to 19.8 micron in the different regions, in contrast to the 25.4 micron mean diameter of hypothalamic magnocellular vasopressin neurons, or the 13.7 micron mean diameter of parvocellular vasopressin neurons in the suprachiasmatic nucleus. No vasopressin neurons were found in other brain and spinal cord regions under the conditions used in this study, although all regions were examined. No oxytocin neurons other than those previously described in the hypothalamus and immediately contiguous regions were found. Measurement of the mean diameter of oxytocin neurons showed that neurons in the caudal paraventricular nucleus were clearly smaller (18.9 micron) than magnocellular oxytocin neurons (24.8 micron) in other parts of the hypothalamus. These parvocellular oxytocin neurons with experimentally documented central connections were similar in both size and appearance to the parvocellular vasopressin neurons seen after colchicine treatment, which are potential sources of certain central vasopressin pathways. These findings indicate that there are at least two types of oxytocin neurons in the hypothalamus and several types of vasopressin neurons in a variety of different areas in the brain, many of which are outside of the hypothalamus.

The vasopressinergic innervation of the brain in normal and castrated rats

A detailed description is given of the distribution of vasopressin-immunoreactive structures in the brain of intact adult male rats. By application of a modified immunocytochemical procedure, vasopressin-immunoreactive fibers were detected in many new areas. In adult male rats which were castrated 15 weeks before death, vasopressin-immunoreactive cell bodies had disappeared from the bed nucleus of the stria terminalis and the medial amygdaloid nucleus. No obvious changes were found in vasopressin-immunoreactive cell bodies in other areas. Furthermore, a very strong reduction was seen in the density of vasopressin-immunoreactive fibers in the olfactory tubercle, nucleus of the diagonal band and its immediate surroundings, ventral pallidum, basal nucleus of Meynert, lateral septum, septofimbrial nucleus, ventral hippocampal formation, amygdaloid area, pre- and supramammillary nucleus, supramammillary decussation, (inter)dorsomedial, parafascicular, and ventral aspect of paraventricular thalamic nuclei, zona incerta, lateral habenular nucleus, ventral tegmental area, substantia nigra, periventricular gray, dorsal and median raphe nucleus, and locus coeruleus. No changes were observed in other areas containing vasopressin-immunoreactive fibers. These changes following gonadectomy were not observed in castrated rats which had been treated with testosterone. The results suggest that vasopressin projections from the bed nucleus of the stria terminalis and possibly from the medial amygdaloid nucleus require the presence of gonadal hormones for their normal appearance. This is in contrast to pathways arising from the hypothalamic vasopressin-producing nuclei, which fail to show obvious changes following castration.

The effects of transverse cuts caudal to the preoptic recess on the fine structure of paraventricular nuclei in rats

Lesions of the tissue surrounding the preoptic recess (anteroventral third ventricle (AV3V) region) have been shown to severely impair normal mechanisms of body fluid homeostasis, including the antidiuretic response. In an earlier investigation of the pathways affected by these lesions, coronal cuts were placed between the level of the organum vasculosum lamina terminalis in the AV3V region and the level of the supraoptic nuclei. Rats with such cuts exhibited hyperdipsia and polyuria, but their plasma levels of antidiuretic hormone (ADH) were elevated. The fine structure of the supraoptic nucleus, a major site of ADH production, and of the neural lobe of the hypophysis, where ADH is released, were observed in rats with similar cuts. Although neural lobes showed evidence of hormone depletion and degenerating axons and terminals were present in supraoptic nuclei, there was no morphological evidence that neurosecretory cell bodies in supraoptic nuclei were affected by these cuts. Therefore, in this investigation we observed the ultrastructural effects of such cuts on paraventricular nuclei, which are the other major source of ADH. Degenerating axons and terminals were common in paraventricular nuclei of lesioned rats, both in the major magnocellular subnucleus and in the periventricular region. Cell bodies and nuclei of neurosecretory cells were not significantly larger in lesioned animals, but morphometric evaluations revealed dispersion of the Golgi complex and alterations in the rough endoplasmic reticulum of the cells. In addition, more multiple nucleoli were present, and nucleoli tended to lie adjacent to the nuclear envelope more frequently. We conclude that the neurosecretory cells in the paraventricular nuclei become more active in rats with these knife cuts.

Extranuclear axon collaterals of paraventricular neurons in the rat hypothalamus: intracellular staining, immunocytochemistry and electrophysiology

Recent studies have suggested that some paraventricular nucleus (PVN) neurons projected to more than one target and, thereby, perhaps coordinate some aspects of seemingly diverse functions. We have systematically investigated the existence, location, hormonal contents and functional integrity of some axon collaterals arising from PVN neurons. This was done using intracellular injections of the fluorescent dye, Lucifer Yellow, extracellular ejections of horseradish peroxidase (HRP), immunocytochemistry with antisera directed against vasopressin (VP) and oxytocin (OX) and electrophysiological analysis of synaptic activation of perifornical neurons in response to electrical stimulation of the PVN in hypothalamic slices. Each of the three morphological techniques revealed clear axon collaterals, arising in the lateral hypothalamus and generally ventrolateral to the PVN. Most branching axons appeared to have a small number of branch points, and many collaterals appeared to terminate near their parent axon. Electrical stimulation of the PVN was found to activate synaptically perifornical neurons located in the areas where the other methods revealed collaterals. Stimulation outside of the nucleus was ineffective unless current intensities were increased 10-30-fold over those applied to the PVN. We conclude that many PVN neurons, at least some of these containing OX and other VP, give rise to axons that branch in the perifornical and more ventral lateral hypothalamus, and that some of their collaterals probably terminate on neurons close to the PVN.

Evidence for the coexistence of glutamate decarboxylase and Met-enkephalin immunoreactivities in axon terminals of rat ventral pallidum

Evidence for the coexistence of glutamate decarboxylase (GAD) and Met-enkephalin (Met-Enk) in axon terminals of ventral pallidum was demonstrated by colocalization of anti-GAD and anti-Met-Enk immunoreactivities in alternate adjacent 1 micron serial sections. Conventional electron microscopy of immunostained ventral pallidum confirmed that the immunoreactive structures were boutons which made predominantly symmetrical synapses on ventral pallidal cell bodies and dendrites.

The noradrenergic innervation of vasopressin neurons in the paraventricular nucleus of the hypothalamus: an ultrastructural study using radioautography and immunocytochemistry

Immunocytochemical and radioautographic procedures were combined at the ultrastructural level to study the noradrenergic synaptic input to vasopressin neurons in selected portions of the paraventricular nucleus of the hypothalamus (PVN) of the rat. Radioactive norepinephrine (NE) was infused into the lateral ventricle or applied topically to the region of the PVN. After appropriate survival times, brain tissues were processed for ultrastructural immunocytochemical demonstration of vasopressin using a monoclonal antibody. [3H]NE varicosities were detected by electron microscopic radioautography. In the periventricular zone of the PVN, radioactive varicosities were numerous accounting for 20-30% of all nerve terminals in this zones. These NE terminals primarily innervated dendritic processes of non-vasopressinergic neurons. Although an occasional axosomatic synapse was observed, input to vasopressin positive neurons was exclusively to their dendrites. In the lateral magnocellular sub-nucleus of the PVN (designed pvl2), noradrenergic terminals were fewer in number accounting for only 1-2% of the total. These terminals were found predominately but not exclusively making axodendritic synapses onto non-vasopressin processes. In both regions, many of the radiolabeled terminals had well-defined membrane appositions with their post-synaptic partners which included a synaptic cleft and post-synaptic density of varying thickness. In both the periventricular zone and the lateral magnocellular regions, noradrenergic varicosities were seen in close proximity to numerous blood vessels.

Tyrosine hydroxylase-immunoreactive neurons of the hypothalamus: a light and electron microscopic study

The localization and morphology of neurons, processes, and neuronal groups in the rat hypothalamus containing tyrosine hydroxylase-like immunoreactivity were studied using an antiserum to bovine tyrosine hydroxylase. This antiserum was thoroughly characterized by precipitation of enzyme activity, immunoblotting, and precipitation of cell-free translation products; a single molecular weight band was recognized by the antiserum. Absorption of the antiserum with purified tyrosine hydroxylase abolished immunocytochemical staining, while addition of bovine dopamine beta-hydroxylase had no effect on immunostaining. Immunoreactive cells were found throughout the hypothalamus. Significant numbers of cells were found in the arcuate, periventricular, dorsomedial hypothalamus/zona incerta, posterior hypothalamic regions (A11-A14), and paraventricular nucleus, as previously described, and in addition, in the preoptic area, adjacent to the anterior commissure, medial and lateral to the suprachiasmatic nucleus, dorsal to and in the supraoptic nucleus, at the lateral borders of the ventromedial nucleus, and in the dorsal and ventral lateral hypothalamus. None of the immunoreactive cell groups are totally separated from adjacent cell groups. Dendritic overlap occurs between any two adjacent groups. From cell counts of 30 micron coronal sections, we estimate the hypothalamus has about 12,000 cells based on raw counts, or 8000 immunoreactive cells after correction for possible split cells. Mean soma size varied considerably from one immunoreactive group to another. Cells in the caudal part of the dorsomedial hypothalamus/zona incerta region were the largest, with a mean diameter of 25 micron, while cells in the anterior commissural and posterior hypothalamic group were among the smallest, with mean diameters of 10 micron. The largest immunoreactive cells in the hypothalamus had volumes in excess of ten times greater than the smallest immunoreactive cells. Tyrosine hydroxylase immunoreactivity was found in dendrites in every region of the hypothalamus, sometimes extending hundreds of micrometers from the perikaryon of origin. Although adjacent cell groups were not distinctly separated, the dendritic arbors of the different cell groups differed greatly. Dendritic and somatic appendages were found on some cells, particularly in the paraventricular nucleus. Immunoreactive dendritic arbors were particularly large in cells seen on horizontal sections through the caudal dorsomedial hypothalamic group and through the anterior hypothalamus. Only slight dendritic trees were observed in the rostral dorsomedial hypothalamus/zona incerta region, and in the pericommissural group.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuronal/glial plasticity in the supraoptic dendritic zone: dendritic bundling and double synapse formation at parturition

The magnocellular neurosecretory cells of the supraoptic nucleus increase production and release of oxytocin and/or vasopressin under such conditions as parturition, lactation and dehydration. These stimuli have been shown to result in increased direct apposition of neuronal membranes and the formation of double synapses (one presynaptic terminal contacting two postsynaptic elements) within the supraoptic nucleus at the level of the cell bodies. These morphological changes are due to the retraction of the thin glial processes which are normally interposed between adjacent neurons. The present study was undertaken to ascertain whether, and to what extent, neuronal/glial plasticity occurs in the dendritic zone (i.e. the ventral glial laminar area) of the supraoptic nucleus. The instances of two or more dendrites with membrane in direct apposition (dendritic bundles), the number of dendrites per bundle, the amount of dendritic membrane in direct apposition and the percentage of dendrites contacted by double synapses were quantified at the ultrastructural level in virgin female, prepartum (21 days of gestation), postpartum (day of parturition) and lactating rats. All parameters measured varied significantly with the hormone demand states created by pregnancy and lactation, apparently due to glial retraction. Moreover, in the 2-24 h period between pre- and postpartum there was a significant increase in the number of dendrites per bundle, dendritic membrane in direct apposition and the percentage of dendrites contacted by double synapses. This time course corresponds to the known increased release of oxytocin and vasopressin at parturition. These findings constitute the first demonstration that dendritic bundles and double synapses occur in the ventral glial lamina/dendritic zone of the supraoptic nucleus and vary under the physiological conditions of pregnancy, parturition and lactation.

Comparison of epidermal growth factor binding and receptor distribution in normal human epidermis and epidermal appendages

To localize epidermal growth factor (EGF) receptors in normal human epidermis and other skin structures, two different light microscopic methods were used. EGF binding [( 125I]EGF/R) to the extracellular portion of the EGF receptor was studied by incubating intact skin samples with [125I]EGF, sectioning the tissues, and performing autoradiography. Immunoreactive EGF receptor molecules (IR-EGF/R) were localized with a mono-specific anti-EGF receptor antibody using a 2-step indirect immunocytochemical method (horseradish peroxidase) and detergent permeabilized tissues. This latter method measured the total pool of EGF receptors: occupied and/or internalized forms, precursor forms, and partially degraded forms of the EGF receptor that retain immunoreactivity. Both the [125I]EGF/R and IR-EGF/R localization studies indicated that EGF receptors were present in basal epidermal keratinocytes, sebocytes, outer root sheath cells in hair follicles, smooth muscle cells of arrector pili muscles, and dermal arteries. The highest levels of [125I]EGF/R and IR-EGF/R were found in the dermal ducts of eccrine sweat glands. The distribution of both [125I]EGF/R and IR-EGF/R was not consistent with the concept that EGF exclusively is involved in cellular division and proliferation in normal human epidermis and its appendages, i.e., EGF receptors were also found in tissues that do not undergo rapid proliferation. The present study indicates that EGF may have a more complex regulatory role in the skin than was previously thought.

Fine structure of histaminergic neurons in the caudal magnocellular nucleus of the rat as demonstrated by immunocytochemistry using histidine decarboxylase as a marker

The morphology of histamine-containing neurons in the caudal magnocellular nucleus was light and electron microscopically examined by means of peroxidase-antiperoxidase (PAP) immunocytochemistry with histidine decarboxylase (HDC) as a marker. HDC-like immunoreactive (HDCI) neurons had large (25-30 microns in diameter) perikarya from which two to four primary dendrites arose. The perikarya had a nearly round nucleus and well-developed Golgi apparatus in addition to a large number of mitochondria and rough endoplasmic reticulum. Immunoreactive endproducts were found diffusely throughout the perikarya, dendrites, and axons. HDCI neurons made synaptic contact with nonreactive axon terminals on the perikarya and dendrites. In addition, the HDCI neurons very frequently formed puncta adherentia with neuronal elements, either HDCI or nonreactive, or glial cells. Most of the HDCI axon terminals serially observed under electron microscopy did not exhibit typical synaptic contact in the caudal magnocellular nucleus. These findings suggest the nonsynaptic release of histamine in the caudal magnocellular nucleus.

Immunoelectronhistochemical evidence for innervation of brain microvessels by vasopressin-immunoreactive neurons in the rat

Peroxidase-antiperoxidase (PAP) immunocytochemistry at the electron microscopic level was used to describe the fine structural characteristics of vascular connections between vasopressin (VP)-immunoreactive neuronal elements and cerebral microvessels in the rat. In the majority of connections, somata or neural processes (mainly dendrites) showing VP-like immunoreactivity were separated from the vessel wall by thin glial processes. In addition, some VP-positive elements could establish direct contacts with the basal lamina of the endothelium or of a pericyte associated with the capillary bed. The findings provide immunocytochemical evidence that the vasopressinergic neuronal elements can directly innervate microvessels in the brain and thereby participate in regulating the local permeability of and the flow through the cerebral microvessels.

Distribution of tyrosine-hydroxylase-immunoreactive neurons in the hypothalamus of rats

The distribution and morphology of cells containing tyrosine hydroxylase (TH) immunoreactivity in the hypothalamus of rats were studied by using a modified immunoperoxidase technique. The TH cell system is more complexly organized than was previously thought. On the basis of their clustering patterns, hypothalamic TH neurons could be subdivided into two groups: dorsal and ventral. The ventral group consists of a prominent aggregate of cells located in the caudal part of the arcuate nucleus. From here, cells extend around the caudal part of the ventromedial and dorsomedial nuclei and the base of the diencephalon. Tyrosine hydroxylase-positive cells are present throughout the arcuate nucleus, except in its ventromedial part. Anteriorly, immunoreactive cells appear in the suprachiasmatic and supraoptic nuclei, in the retrochiasmatic area, and in the ventral part of the anterior hypothalamic nucleus. The dorsal group has its main concentration of cells in the medial part of the zona incerta, from which two clusters of cells, one medial and one lateral, extend rostralward. The medial group comprises cells in the medial part of the dorsomedial, paraventricular, and anterior hypothalamic nuclei. These cells adjoin the periventricular cells. The lateral group of cells emanating from the zona incerta occupies the lateral part of the dorsomedial and anterior hypothalamic nuclei and the dorsal hypothalamic area. The dorsal and ventral TH cell groups are in continuity medially in the periventricular layer, and laterally through the cells that surround the ventromedial nucleus. Although the cells vary widely in size, shape, and dendritic arborization pattern, there are two main cell types. Small (21 X 11 microns), round to fusiform cells, with two or three dendrites arborizing simply, were frequently seen in the arcuate, suprachiasmatic, periventricular, supramammillary nuclei and at the borders of the ventromedial nucleus. The other cell type is larger (40 X 15 microns) and multipolar, with three to five frequently branching dendrites. The dendritic field is large and the cells are intensely TH-immunoreactive. Although the larger cells occur occasionally in every hypothalamic nucleus, their principal locations are in the dorsal parts of the dorsomedial, posterior hypothalamic nuclei and the dorsal and lateral parts of the zona incerta, and in the areas dorsal and medial to the mammillothalamic tract at caudal hypothalamic levels. In this paper we give a detailed description of TH-immunoreactive fibers and terminals in the hypothalamus and a comparison with previous studies of catecholamine cells in the hypothalamus.

Fine structural studies of cholecystokinin-8-like immunoreactive neurons and axon terminals in the nucleus of tractus solitarius of the rat

Cholecystokinin (CCK)-8-like immunoreactive structures in the nucleus of tractus solitarius (NTS) were studied by using the peroxidase-antiperoxidase (PAP) immunohistochemical method. Immunoreactivity was localized in cell bodies and nerve fibers. The perikarya were oval or fusiform (average length 13 micron) and were mostly located in the dorsal half of the medial subnucleus of the NTS at the level of the area postrema (AP). One to three straight immunoreactive dendritelike processes emerged from the perikarya. Neurons that had first been identified under light microscopy were also studied by electron microscopy. Each neuron had a moderate amount of cytoplasm and an oval or elongated nucleus that was eccentrically located in the soma. A few synaptic inputs were found on the CCK immunoreactive perikarya, while a moderate number were seen on both proximal and distal dendrites. These neurons received both asymmetrical and symmetrical synaptic inputs. The immunoreactive dendrites were most frequently in asymmetrical synaptic contact with nonreactive boutons (max. 2.7 micron in diameter) containing fairly densely packed, small round vesicles. CCK immunoreactive boutons located in the NTS at the level of the AP were analyzed using electron microscopy; these boutons formed asymmetrical synaptic contact with other neuronal elements. Their postsynaptic targets were immunoreactive and nonreactive perikarya and dendrites. These data suggest that CCK-containing afferents might affect the neurotransmission of heterogenous types of solitary neurons.

Intrinsic inhibition in magnocellular neuroendocrine cells of rat hypothalamus

Endogenous mechanisms of inhibition in magnocellular neuroendocrine cells were studied with intracellular recordings in the rat hypothalamic slice preparation. Hyperpolarizing after-potentials (duration up to 125 ms) followed single action potentials and after-hyperpolarizations (a.h.p.s) lasting hundreds of milliseconds followed brief evoked spike trains. The amplitude and duration of the a.h.p. increased after spike trains of longer duration or higher frequency. The a.h.p. appears endogenous, rather than synaptically mediated from recurrent inhibition, because it persisted after pharmacological blockade of axonal conduction or of chemical synaptic transmission. The reversal potential of the a.h.p. was at least 20 mV more negative than that of inhibitory post-synaptic potentials. Cl- ionophoresis did not alter the a.h.p. Chelation of intracellular Ca2+ with EGTA injection eliminated the a.h.p. A Ca2+-activated K+ conductance, rather than recurrent synaptic inhibition, apparently causes the a.h.p. and is at least partly responsible for the inhibition after single spikes in magnocellular neurones. During hormone release, this endogenous mechanism may contribute to the post-burst silent period in putative oxytocinergic cells and to the interburst interval in phasic neurones, which are known to fire repetitive bursts associated with vasopressin release.

Electrophysiological evidence for facilitatory control of oxytocin neurones by oxytocin during suckling in the rat

Antidromically identified paraventricular neurones were recorded simultaneously with intramammary pressure in urethane (1.2 g/kg) anaesthetized rats during suckling. The correlation of the firing pattern of these neurones with milk ejection enabled distinction between oxytocin and vasopressin neurones. Oxytocin neurones displayed a short (2-6 s) characteristic high-frequency burst of spikes. This activation probably occurred simultaneously in all oxytocin neurones 12-18 s before milk ejection and was regular in both frequency and amplitude (total number of spikes). The role of neurohypophysial peptides and analogues in the control of these characteristics was studied. Injecting 10 pg, 100 pg and 1 ng of oxytocin into the 3rd ventricle increased background activity of slow-firing oxytocin neurones (less than 3 spikes/s) and had a strong dose-dependent facilitatory effect on the milk ejection reflex, increasing both the amplitude and frequency of neurosecretory bursts. No effect was observed on non-neurosecretory neurones. Such injection also triggered the milk ejection reflex when it had not appeared an hour after suckling began. Oxytocin did not itself induce neurosecretory activation, which only appeared if the young rats were sucking. Injecting oxytocin into the lateral ventricle was less effective than into the 3rd ventricle. No effect was observed after injection into the venous blood or into the 4th ventricle, which suggested that oxytocin acts in the hypothalamus. Injecting mesotocin or isotocin into the 3rd ventricle had a facilitatory effect similar to that of oxytocin but vasopressin, vasotocin, MIF I (pro-leu-gly-NH2, terminal triplet oxytocin) or bovine neurophysins I and II did not modify neurosecretory activation or the milk ejection pattern. Injecting an oxytocin antagonist, ([1(beta-mercapto-beta, beta cyclopentamethylene propionic acid), 8-ornithine] vasotocin, d(CH2)5OVT) into the 3rd ventricle decreased milk ejection frequency and considerably delayed the reappearance of the first milk ejection. This resulted from a decrease in both frequency and amplitude of neurosecretory bursts, which were too small to induce detectable oxytocin release. Moreover, d(CH2)5OVT suppressed the facilitatory effect of exogenous oxytocin. Under normal conditions, endogenous oxytocin seemed to be involved in the control of neurosecretory activation. Injecting 1 ng oxytocin or 1 or 10 ng vasopressin into the 3rd ventricle did not modify the firing pattern of vasopressin neurones whether activated by hyperosmotic stimulation (1 ml NaCl, 9% solution (w/v) I.P.) or not.(ABSTRACT TRUNCATED AT 400 WORDS)

Slice cultures of cerebellar, hippocampal and hypothalamic tissue

Cerebellar, hippocampal and hypothalamic slices prepared from newborn and 7-day-old rats were cultured by means of the roller-tube technique. Identification of cells was made easier by the fact that at least part of the characteristic cytoarchitecture of the tissue was preserved in vitro. Cerebellar Purkinje cells and neurones of the deep cerebellar nuclei were recognized on the basis of their size, their location within the culture and their dendritic arborization. Pyramidal cells of all hippocampal subfields displayed their characteristic basal and apical dendritic trees with numerous spinous processes. Hippocampal granule cells gave rise to a monopolar dendritic arbor; their axons terminated in the dentate hilus and CA3 region. Golgi-like immuniperoxidase staining allowed localization of groups of neurophysin-positive neurones in slices prepared from the anterior hypothalamus. These neurones, bilaterally bordering the third ventricle, usually displayed a simple dendritic arborization and fine beaded axons. - Cultivation of brain slices prepared from young rats offers particular advantages in that the cultured cells are organized in an organotypic monolayer and individual living neurones may be directly visualized.

Golgi-like immunoperoxidase staining of dopamine neurons in the reticular formation of the rat brainstem using antibody to tyrosine-hydroxylase

The distribution and morphology of presumed dopaminergic neurons within the reticular formation (RF) and the ventrolateral tegmental area (VLT) were studied by using a specific antibody to the enzyme that converts tyrosine to dihydroxyphenylalanine, tyrosine-hydroxylase (TH), in combination with a sensitive immunoperoxidase method (Hsu et al., '81). Incubation of thick (70-120 micron) sections for 3-5 days in high dilutions of antibody resulted in staining of TH-immunoreactive neurons in a Golgi-like fashion. Analysis of serial sections cut in the coronal, horizontal, and parasagittal planes revealed an extensive system of TH-positive neurons in the RF and VLT extending from the Edinger-Westphal nucleus caudally to the level of the decussations of the superior cerebellar peduncle. Within this region, the TH-positive cells belong to two subgroups: (1) a relatively well-defined population of cells aggregated in the reticular formation (corresponding to cell group A8 of Dahlström and Fuxe, '64), and (2) a more loosely defined group of cells that appears to be continuous with the cells of the nucleus raphe linearis. This latter cell group extends laterally from the midline to the nucleus parapeduncularis. An analysis of the individual TH-immunoreactive cells revealed large differences in their morphology. Thus, the somata of TH-positive cells in the RF and the VLT are fusiform, ovoid, or triangular. A majority of the TH neurons are of medium (long axis: 15-35 micron) to large (long axis: 35-40 micron size. While the cells in the A8 area appeared relatively homogeneous, the TH-positive cells of the VLT showed great variations in dendritic branching pattern and orientation. Taken together, the present study has shown that within the RF and the VLT, the TH-immunoreactive neurons are more numerous than hitherto recognized, and that this cell group consists of a morphologically heterogeneous population of dopamine-synthesizing neurons.

Study of the efferent connections of the enkephalinergic magnocellular dorsal nucleus in the guinea-pig hypothalamus using lesions, retrograde tracing and immunohistochemistry: evidence for a projection to the lateral septum

The efferents of enkephalin-immunoreactive neurons in the magnocellular dorsal nucleus of the guinea-pig were studied using different neuroanatomical methods and indirect immunocytochemical technique. Following unilateral implantation of the fluorescent dye 4',6-diamidino-2-phenylindole in the lateral septal nucleus, retrogradely-labeled perikarya were found in the magnocellular dorsal nucleus. These labeled perikarya reacted with antiserum against enkephalin, demonstrating that enkephalin-immunoreactive neurons in the magnocellular dorsal nucleus project to the lateral septal nucleus. In other experiments, complete bilateral lesions were produced in the magnocellular dorsal nucleus by electrocoagulation. Enkephalin-immunoreactive nerve fibers and terminals were totally depleted in the lateral septal nucleus. This confirms that septal enkephalin-immunoreactive terminals originate in the magnocellular dorsal nucleus and further suggests that this nucleus is the source of all the enkephalin-immunoreactive material found in the septum. Experiments utilizing two different fluorescent dyes, 4',6-diamidino-2-phenylindole and propidium iodide, injected in each side of the lateral septal nucleus, respectively, demonstrated that the magnocellular dorsal nucleus gives off axon collaterals to both sides of the septum, since double-labeling of individual cell bodies was detected in the nucleus. By relating this finding to the results obtained after unilateral destruction of the nucleus, which caused an incomplete loss of enkephalin- immunoreactive material in the lateral septal nucleus ipsilaterally, it is suggested that the enkephalinergic hypothalamo-septal pathway contains unbranching neurons projecting ipsilaterally and branching neurons distributing fibers ipsilaterally and contralaterally. Lesion experiments, and experiments based on the retrograde axonal transport of horseradish peroxidase after intravenous injections, demonstrated that the magnocellular dorsal nucleus contributes neither to the tubero-infundibular nor to the hypothalamo-neurohypophyseal tracts. The lateral septal nucleus receives numerous aminergic and peptidergic projections, indicating the potential importance of this region in physiological and behavioral events. In the guinea-pig, the well-demarcated enkephalinergic pathway demonstrated in this study provides a convenient model for the experimental study of the enkephalinergic innervation of the lateral septal nucleus.

Axon collaterals of supraoptic neurones: anatomical and electrophysiological evidence for their existence in the lateral hypothalamus

The magnocellular neurones of the supraoptic nucleus which synthesize and secrete vasopressin and oxytocin have been commonly regarded as simple "output" neurones in that they receive an input, generate an action potential and in turn release hormone from their terminals in the posterior pituitary. Three lines of evidence are presented which suggest that rat supraoptic nucleus neurons also have axon collaterals which terminate in the hypothalamus close to the nucleus. Small injections of horseradish peroxidase were made directly into the nucleus in hypothalamic slices, allowing visualization of the axons of supraoptic neurones. Collaterals of these axons could be observed in regions both dorsal and dorsolateral to the supraoptic nucleus. In a separate series of experiments, sections of perfusion-fixed hypothalamus were stained for vasopressin and oxytocin using specific antisera. Peptide-containing collaterals of both types were observed near the supraoptic nucleus, in a region similar to that seen after horseradish peroxidase injections. Finally, electrophysiological studies were carried out on hypothalamic slices containing the supraoptic nucleus. A small concentric bipolar stimulating electrode was placed directly into the nucleus and activity of lateral hypothalamic neurones within 0.1-1 mm of the nucleus was recorded. Of 68 neurones studied, 52 were excited by supraoptic stimulation via a synaptic pathway that could be blocked by Ca2+ -free solutions containing 18 mM Mg2+. These studies suggest that supraoptic neurones communicate via axon collaterals with other neurones in the lateral hypothalamus, in addition to their previously well characterised functional role in neurosecretion.

Synaptic input to vasopressin neurons of the paraventricular nucleus (PVN)

Following injections of horseradish peroxidase into the PVN, retrogradely filled cells were found in regions of the limbic system known to contain glucocorticoid concentrating neurons [4, 31, 44]. To determine if these regions which include the lateral septum, medial amygdala and ventral subiculum have a monosynaptic input to vasopressin neurons we developed a double label ultrastructural technique [20] to simultaneously visualize immunoreactive neuropeptide and anterogradely transported HRP. Following injections of tracer into all three of these regions, HRP labeled fibers were seen at the light microscopic level to form a halo in the perinuclear, cell poor zone around the PVN. Ultrastructural examination of this area resulted in the discovery of a small number of limbic system synapses on vasopressin dendrites. These synapses were most numerous in the ventral and medial portion of the cell poor zone. A similar pattern of innervation was seen for the supraoptic and suprachiasmatic nucleic which also contain vasopressin cells whose dendrites extend beyond the nuclear boundaries. In a similar fashion we were interested in determining the distribution of noradrenergic terminals on vasopressin neurons in the various subnuclei of the PVN. We have combined immunocytochemistry for vasopressin with radioautography for 3H-norepinephrine (NE) at the ultrastructural level. NE terminals were numerous in the periventricular zone, innervating both vasopressin containing dendrite and non-immunoreactive dendrites and cell bodies. The vasopressin dendrites could originate from cells either resident in the periventricular zone or from cells situated in more lateral subnuclei. In the main, lateral magnocellular region, noradrenergic terminals were very few in number and innervated almost exclusively non-vasopressin containing structures. These studies demonstrate the need for ultrastructural analysis of synaptic input to neurosecretory cells.

Immunocytochemically identified vasopressin neurons in culture show slow, calcium-dependent electrical responses

From morphological characterization and intracellular recordings, monolayer cultures derived from fetal mouse hypothalami were found to include functionally differentiated peptide neurons, a number of which appear to contain vasopressin. These cells exhibited particular patterns of slow, calcium-dependent membrane depolarizations, resembling in their periodicity and duration the phasic activity of vasopressin neurons recorded extracellularly in vivo.

Selective increase of angiotensin-converting enzyme activity in discrete extrahypothalamic areas of Brattleboro rats

We studied the activity of angiotensin I converting enzyme (ACE, kininase II, E.C. 3.4.15.1) in discrete areas of the brainstem and limbic system, and in circumventricular organs, pineal gland and choroid plexus of homozygous Brattleboro rats (DI) which are characterized by vasopressin deficiency and diabetes insipidus, with or without vasopressin replacement. We also determined ACE activity in heterozygous Brattleboro (HZ) and Long-Evans (LE) control rats. We found changes in ACE activity in several brain areas and the pineal gland of Brattleboro rats. ACE activity was increased in DI rats with respect to HZ and LE controls in the A1 area of the brainstem, locus coeruleus, and triangular nucleus of the septum. ACE activity in the A2 area of the brainstem, the nucleus tractus spinalis nervi trigeminii and the pineal gland was enhanced in both HZ and DI rats with respect to that of LE controls, but was not different between HZ and DI rats. ACE activity did not change in the other extrahypothalamic areas studied. The elevated ACE activity in extrahypothalamic areas of DI rats was not reversed by vasopressin replacement. These results suggest that a relationship between central vasopressin and angiotensin or bradykinin systems may exist in selective extrahypothalamic areas of the rat brain, and that peripherally administered vasopressin cannot influence this relationship.

The section-Golgi impregnation procedure. 2. Immunocytochemical demonstration of glutamate decarboxylase in Golgi-impregnated neurons and in their afferent synaptic boutons in the visual cortex of the cat

Sections of the cat's visual cortex were stained by an antiserum to glutamate decarboxylase using the peroxidase-antiperoxidase method; they were then impregnated by the section Golgi procedure and finally the Golgi deposit was replaced by gold. Neurons containing glutamate decarboxylase immunoreactivity were found in all layers of the visual cortex, without any obvious pattern of distribution. Fifteen immunoreactive neurons were also Golgi-impregnated and gold-toned, which enabled us to study the morphology and synaptic input of identified GABAergic neurons. These neurons were found to be heterogeneous both with respect to the sizes and shapes of their perikarya and the branching patterns of their dendrites. All the immunoreactive, Golgi-impregnated neurons had smooth dendrites, with only occasional protrusions. The synaptic input of glutamate decarboxylase-immunoreactive neurons was studied in the electron microscope. Immunoreactive neurons received immunoreactive boutons forming symmetrical synapses on their cell bodies. The Golgi-impregnation made it possible to study the input along the dendrites of immunoreactive neurons. One of the large neurons in layer III whose soma was immunoreactive was also Golgi-impregnated: it received numerous non-immunoreactive asymmetrical synaptic contacts along its dendrites and occasional ones on its soma. The same neuron also received a few boutons forming symmetrical synaptic contacts along its Golgi-impregnated dendrites; most of these boutons were immunoreactive for glutamate decarboxylase. Glutamate decarboxylase-immunoreactive boutons were also found in symmetrical synaptic contact with non-immunoreactive neurons that were Golgi-impregnated. A small pyramidal cell in layer III was shown to receive several such boutons along its somatic membrane. It is concluded that the combination of immunoperoxidase staining and Golgi impregnation is technically feasible and that it can provide new information. The present study has shown that there are many morphologically distinct kinds of aspiny GABAergic neurons in the visual cortex; that the predominant type of synaptic input to the dendrites of such neurons is from boutons forming asymmetrical synapses, but that some of the GABAergic neurons also receive a dense symmetrical synaptic input on their cell bodies, and occasional synapses along their dendrites, from the boutons of other GABAergic neurons. These findings provide a morphological basis, firstly, for a presumed powerful excitatory input to GABAergic interneurons and, secondly, for the disinhibition which has been postulated from electrophysiological studies to occur in the cat's visual cortex.

Centrally mediated effects of neurohypophyseal hormones

The neurohypophyseal hormones oxytocin and vasopressin cause a variety of biological effects in animals which are mediated by central nervous system mechanisms. Among the best studied of these effects is the modulation of both memory processes and the development of drug tolerance and dependence. Neurohypophyseal hormones have also been shown to alter various physiological parameters such as heart rate and body temperature following central administration. In addition, these peptides can profoundly alter spontaneous, unlearned behavior in several rodent species. Many of the centrally mediated effects of neurohypophyseal hormones have been shown to be elicited at sites within the brain stem and the limbic system where vasopressin and oxytocin occur in cell bodies, axons and nerve terminals, suggesting a physiological role for these peptide effects. The various central effects of neurohypophyseal hormones involve different mechanisms which can be distinguished from one another on the basis of required dose, time-course of action, and structure-activity relationships. Thus, alterations of spontaneous behavior are mediated by putative receptors closely related to vasopressin receptors in blood vessels responsible for the peripheral pressor response while the effects on memory processes are mediated by a mechanism which is not closely related to those involved in the peripheral hormonal effects of the peptides. The influence of neurohypophyseal hormones on memory and attention may be useful clinically. A potential role for these peptides in mental disorders is discussed.

Ultrastructural demonstration of ovine CRF-like immunoreactivity (oCRF-LI) in the rat hypothalamus: processes of magnocellular neurons establish membrane specializations with parvocellular neurons containing oCRF-LI

Ovine corticotropin releasing factor-like (oCRF-LI) immunoreactivity was detected in the rat hypothalamus by immunocytochemistry. The unlabeled antibody peroxidase-antiperoxidase method was applied in 40 microM vibratome sections before embedding for examination under the electron microscope. Immunoreactivity was found in axons of the median eminence and the neural lobe, as well as in cell bodies and dendrites of parvocellular neurons the in paraventricular nucleus. Axon terminals in the external zone of the median eminence and in the neural lobe frequently abutted on the pericapillary space, suggesting the possible release of oCRF-LI into the fenestrated capillaries. Labeled cells in the paraventricular nucleus synapsed with unlabeled nerve terminals and were found in synaptic-like contact with protrusions of magnocellular neurons. The latter finding might represent the morphological basis for orthodromic interactions between parvocellular and magnocellular neurons of the paraventricular nucleus, which have been previously demonstrated by electrophysiological methods.

Ultrastructural studies of vasopressin neurons of the paraventricular nucleus of the hypothalamus using a monoclonal antibody to vasopressin: analysis of synaptic input

The ultrastructure of the vasopressin neurons of the paraventricular nucleus of the hypothalamus was studied by immunocytochemical techniques. Tissue antigen was detected in unembedded tissue sections using a monoclonal antibody that recognizes vasopressin but not oxytocin or vasotocin. At the light-microscopic level, reaction product was seen to fill the cytoplasm of the neuron cell body as well as large portions of the dendrite and axon. Immunoreactive spines were seen on both somatic and dendritic surfaces and their presence was confirmed at the ultrastructural level. In the light-microscope, axonal processes do not have spines and are thinner and more varicose than dendritic processes. At the electron-microscopic level, both axons and dendrites of the vasopressin cells are filled with reactive neurosecretory granules. The presence of large numbers of these organelles made it difficult to distinguish proximal dendrites from Herring bodies (axonal swellings). At the ultrastructural level, reaction product was also observed in the cytoplasm of all segments of the vasopressin cells. The presence of reaction product outside of membranous compartments is undoubtably due to disruption of membranes by detergent treatment or exposure to basic pH. However, the staining procedure used did allow us to examine the synaptic input to the vasopressin cells. All portions of the vasopressin neuron receive a diverse innervation. The somata have synapses on their surfaces and on spines. These axo-somatic terminals are primarily, but not exclusively, symmetrical and the presynaptic elements contain spherical or elongate vesicles. On the dendrites, terminals again were observed on the surface or on spines. these axo-dendritic synapses were usually asymmetrical. The presynaptic elements contained clear spherical, elongate or pleomorphic vesicles. Occasional varicosities with dense-core granules were seen to make en passant contacts with dendrites; these contacts did not have obvious membrane specializations. Input to vasopressin axons was studied both along the paraventricular-neurohypophysial tract and in the median eminence. Vasopressin axons receive a synaptic input (axo-axonic), predominately of the asymmetric variety with clear, spherical vesicles in the presynaptic element. These findings demonstrate that the vasopressin neurons of the paraventricular nucleus receive a diverse innervation.

Quantitative histological studies on the hypothalamic paraventricular nucleus in rats: I. Number of cells and synaptic boutons

Quantitative histological analysis of serial sections of the adult male rat brain gives mean total estimates of the numbers of cells in the magnocellular and parvicellular divisions of the paraventricular hypothalamic nuclei (PVN) of 6600 and 11,500, respectively. The numbers and densities (number/mm3) of presynaptic bouton profiles have been measured and calculated on electron micrographs of the magnocellular paraventricular nucleus (mPVN). There are approximately 18 x 10(6) presynaptic boutons in the magnocellular subdivision: 76% of the synaptic boutons are axodendritic, 17% axosomatic and 7% are unidentified but include a few axo-axonic contacts. One third of the boutons contain dense-core vesicles although their postsynaptic contacts do not differ from other boutons. The estimated ratio of the number of boutons per neuron in the magnocellular paraventricular nucleus is 2820:1.

An electrophysiological analysis of caudally-projecting neurones from the hypothalamic paraventricular nucleus in the rat

Using anaesthetized rats, experiments were performed to test whether neurones located in the hypothalamic paraventricular nuclei and sending axons caudally, could be identified electrophysiologically. Neurones projecting caudally were localized by antidromic invasion following electrical stimulation within the region of the dorsal motor nucleus of the vagus, the nucleus of the tractus solitarius and the hypoglossal nucleus. Stimulation of more ventral regions in the medulla oblongata was not effective. Caudally-projecting neurones were dispersed throughout the paraventricular nuclei and were often found close to magnocellular neurones antidromically invaded by stimulation of the pituitary stalk. About one-third of the caudally-projecting neurones were synaptically activated by pituitary stalk stimulation, but only at currents sufficient to antidromically invade the magnocellular neurones. This suggests a synaptic interaction between magnocellular and some caudally-projecting paraventricular neurones. The possible physiological significance of these findings is discussed.

Direct reciprocal connections between the bed nucleus of the stria terminalis and dorsomedial medulla oblongata: evidence from immunohistochemical detection of tracer proteins

Connections between the bed nucleus of the stria terminalis and the dorsomedial medulla oblongata have been examined by immunohistochemical detection of the tracer proteins horseradish peroxidase (HRP) or wheat germ agglutinin (WGA). Two sets of four rats received 0.2 or 0.4 microliter of either tracer injected into the dorsomedial medulla oblongata, were fixed by perfusion 48 hours later, and were processed for immunohistochemical detection of the tracers. Rats receiving HRP showed only a few single neurons retrogradely labelled in the ipsilateral bed nucleus, and some anterogradely labelled fibers. Rats receiving WGA showed a large number of retrogradely labelled neurons in the ipsilateral bed nucleus. Labelled neurons were most concentrated in a group in the central, dorsal, and lateral aspects of the nucleus at the level of the anterior commissure and just caudal to this. Just ventral to this group was a dense cluster of anterogradely labelled fibers. The retrogradely labelled neurons ranged from 12 to 20 microns in size and were multipolar. These findings indicate that there are direct reciprocal connections between the bed nucleus of the stria terminalis and the autonomic centers of the dorsomedial medulla oblongata and strengthen the concept that this nucleus is involved in forebrain integration of autonomic functions.

Immunohistochemical identification of the oxytocin and vasopressin neurons in the hypothalamus of the monkey (Macaca fuscata)

The hypothalamic oxytocin and vasopressin neurons of the monkey, Macaca fuscata, were demonstrated in Golgi-like images by a modified immunoperoxidase method. The magnocellular oxytocin and vasopressin neurons were distributed mainly in the supraoptic and paraventricular nuclei. In addition to these main nuclei, both types of magnocellular neurons were found in the accessory supraoptic nucleus, the periventricular and perifornical areas, the nucleus of the stria terminalis, the lateral hypothalamic area, and the pars interna of the globus pallidus. Magnocellular oxytocin neurons were seen immediately ventral to the anterior commissure, and parvocellular vasopressin neurons were localized in the medial portion of the suprachiasmatic nucleus. The preferential distribution of the oxytocin and vasopressin neurons was recognized not only in the supraoptic and paraventricular nuclei, but also in other areas. In all areas observed, the cytological difference between the oxytocin and vasopressin neurons could be identified. The area of the perikarya of the vasopressin neurons was determined to be larger than that of the oxytocin neurons. Most of the axons of the oxytocin neurons issued from the perikarya, while the axons of the vasopressin neurons originated in most cases from the thick proximal dendrites. These results show that the oxytocin and vasopressin neurons are distributed in areas much broader than has hitherto been assumed, and that these two peptidergic neurons can be definitely differentiated morphologically as well as functionally.

Light- and electron-microscopic characterization of electrophysiologically-identified, horseradish peroxidase-injected magnocellular neuroendocrine cells in goldfish preoptic nucleus

We recorded intracellularly from neurons in the goldfish preoptic nucleus which were antidromically identified by electrical stimulation of the pituitary gland and marked by intracellular injection of horseradish peroxidase for subsequent localization. At the light-microscopic level, labeled neurons resembled profiles of Golgi-impregnated neurons and lay in the magnocellular portion of the preoptic nucleus. Densely labeled axons and dendrites projected to the lateral forebrain bundle, the medial forebrain bundle, fiber tracts in the preoptico-hypophysial tract, small blood vessels and capillaries, the ependymal lining of the third ventricle and toward the preoptic neurons. Occasionally, a lightly-labeled, large perikaryon lay adjacent to a large, heavily-labeled magnocellular neuron. Ultrastructural examination of these identified cells revealed dense reaction product in neuronal perikarya and processes. Heavily labeled perikarya had elaborate networks of endoplasmic reticulum, extensive Golgi apparatus, occasional somatic spines and infrequent axo-somatic contacts from unlabeled neurons. These labeled perikarya which were frequently in close somatic apposition with unlabeled profiles were sometimes adjacent to a large, lightly-labeled perikaryon. A thin glial sheath separated most labeled neurons and processes from brain capillary endothelium. Labeled dendrites had heavily labeled spines and axo-dendritic contacts from unlabeled neurons. Labeled axons abutted unlabeled-axons and -dendrites. Synaptic boutons innervating labeled structures always contained small clear synaptic vesicles and some boutons also contained large dense-core vesicles. These results demonstrate the complex connections of goldfish preoptic magnocellular neuroendocrine cells with other neurons, fiber systems, brain capillaries, ventricular ependyma and the pituitary and provide further support for non-endocrine as well as endocrine functions of magnocellular neurons.

Central neurohypophyseal peptide pathways: interactions with endocrine and other autonomic functions

Electrophysiological and pharmacological studies have been carried out in rats and rabbits to attempt to identify possible functional roles for neurohypophyseal peptides in brain. In anesthetized rats, single unit recordings and antidromic activation criteria were utilized to identify projections of the paraventricular nucleus (PVN) to neurohypophysis and to extrahypothalamic areas (amygdala or nucleus tractus solitarius). None of the cells tested innervated more than one of these areas and, when tested for their responses to haemorrhage, increased body osmolarity, or suckling of pups, only the osmotic stimulus caused increased activity in some cells projecting to amygdala or nucleus tractus solitarius. Indirect evidence as well as direct measurement by radioimmunoassay of arginine vasopressin (AVP) in brain perfusates revealed probable central release of AVP in response to stimuli known to activate pituitary secretion of this peptide. These observations raise the possibility that certain brain and pituitary peptidergic systems may function in a co-ordinated manner.

Cerebrospinal fluid vasopressin and oxytocin: evidence for an osmotic response

A push-pull perfusion technique was used to sample third ventricular cerebrospinal fluid (CSF) in the conscious rat. Ventricular perfusate contained significant quantities of vasopressin and oxytocin, 13.1 and 4.5 pg/ml, respectively. Vasopressin and oxytocin levels were stable over a 3 h perfusion period. High sodium artificial CSF elicited a 4-5-fold stimulation of perfusate concentrations of both peptides. These findings suggest that the CSF represents a dynamic compartment in terms of neuroendocrine function.

The magnocellular and parvocellular paraventricular nucleus of rat: intrinsic organization

The magnocellular and paravocellular regions of the rat hypothalamic paraventricular nucleus (PVN) were examined in several hundred brains. Converging qualitative and quantitative anatomical methods, including Golgi impregnations, Nissl stains, silver stains, and immunocytochemistry were used to study the intrinsic organization of the PVN with light, scanning, and transmission electron microscopy. A computer-assisted quantitative analysis of dendritic branching patterns was used to examine total dendritic length, center of mass, orientation of dendritic tree, and several other parameters of dendritic organization and revealed statistically significant differences between cells in the lateral and posterolateral magnocellular and medial parvocellular areas of PVN. Electron microscopy, Golgi impregnation, and neurophysin immunohistochemistry showed that dendrites of posterolateral cells were generally oriented perpendicular to the third ventricle; dendrites of cells in the lateral PVN usually projected medially from the perikaryon. Cells in the medial zone of PVN had dendritic trees which often paralleled the third ventricle. Large numbers of axons entered and left PVN ventrally near the midline and laterally in the area of the posterolateral PVN; axons generally were oriented parallel to the mean major axis of dendritic trees in these areas. Ultrastructural examination of serial thin sections showed a peculiar astroglia multiple lamellar isolation of axodendritic synaptic contacts. Intrinsic axons commonly arose from parvocellular but not from magnocellular neurons and contacted dendrites of both medial parvocellular and more lateral magnocellular neurons. Synapses were found on shafts and spines of dendrites, on perikarya and somatic appendages, and invaginated into the soma. Both dendrites axons with large neurosecretory vesicles and immunostained with neurophysin antiserum were found postsynaptic to other axons. Presynaptic neurosecretory axons were not found within the PVN. A semiquantitative analysis of catecholamine axons identified with the glyoxylic acid method and fibers immunoreactive with ACTH and Substance P antisera indicated that the parvocellular region of PVN received ggreater innervation than the lateral magnocellular area; similarly, a reater density of stained fibers was found in the medial parvocellular PVN region with Golgi impregnations and silver stains. With a stereological analysis of 1-micrometer plastic sections, the parvocellular area had a significantly greater neuropil to cell volume ration, with cells accounting for 48 +/- 9% in the lateral magnocellular zone, but only for 26 +/- 7% in the parvocellular area. A quantitative analysis of vasculature from thin sections showed that the PVN had 3.3 times more blood vessels, and 3.6 times more lumen perimeter than a control area ventrolateral to PVN; an interesting finding here was that the medial parvocellular PVN had a high degree of vascularity, not significantly different from the lateral magnocellular zone...

Immunocytochemical, Golgi and electron microscopic characterization of putative dendrites in the ventral glial lamina of the rat supraoptic nucleus

Processes of magnocellular neurosecretory cells in the rat supraoptic nucleus which project along the pial surface in the ventral glial lamina were investigated using immunocytochemistry, Golgi stains and electron microscopy. Immunocytochemical studies revealed that although both oxytocin- and vasopressin-containing processes were evident in the ventral glial lamina, vasopressin-containing processes predominated. Ventral processes were thicker and of a different morphology than dorsal axon-like processes which joined the hypothalamo-neurohypophysial tract and exhibited large varicosities along their length or at their apparent termination. Golgi stains revealed that classically defined dendrites of supraoptic neurons projected primarily ventrally and often invaded the ventral glial lamina. No axons were traced to the lamina. Ultrastructurally, processes within the ventral glial lamina characterized as dendrites could be stained immunocytochemically for neurophysin and were post-synaptic to a variety of presynaptic elements. The results suggest that many dendrites from magnocellular neurosecretory cells in the supraoptic nucleus project to the ventral glial lamina and form a restricted, receptive plexus. The previously demonstrated coexistence of catecholamine-containing varicosities and other axon types with these processes in the lamina indicates an important role for supraoptic dendrites in integrating a wide variety of information relevant to neurohypophysial hormone release.

Dendritic trees of neurones in the rat supraoptic nucleus

The cytoarchitecture of the rat supraoptic nucleus was studied using the Golgi-Cox method with a neutral red or Cresyl violet counterstain to allow the limits of the nucleus to be determined accurately. A small number of stained neurones were seen in each of the brains sectioned but they were unevenly distributed in the supraoptic nucleus. There were more cells posteriorly and close to the optic tract. A minority of cells studied (a total of 4) were round (diameter approximately 20 micrograms) and multipolar and were interpreted as interneurones. The majority of stained cells studied (60) had oval cell bodies (mean long diameter 22.7 micrograms in coronal sections) with a single fine axon directed dorsally and medially and 1-3 heavier dendrites passing ventrally. Both cell bodies and dendrites of the major cell type showed spines and both dendrites and axons had some varicosities. The anatomy of the larger cell group (the presumed neurosecretory cells) is thus consistent with their having a substantial synaptic input and the presence of long dendrites (up to 205 micrograms) implies that caution is necessary in the interpretation of experiments where cell activity is monitored while active materials are placed near the cell bodies.