Identification of neurophysin producing cells. I. The origin of the neurophysin-like substance-containing nerve fibres of the external region of the median eminence of the rat

The clock in the brain: neurons, glia, and networks in daily rhythms

The master coordinator of daily schedules in mammals, located in the ventral hypothalamus, is the suprachiasmatic nucleus (SCN). This relatively small population of neurons and glia generates circadian rhythms in physiology and behavior and synchronizes them to local time. Recent advances have begun to define the roles of specific cells and signals (e.g., peptides, amino acids, and purine derivatives) within this network that generate and synchronize daily rhythms. Here we focus on the best-studied signals between neurons and between glia in the mammalian circadian system with an emphasis on time-of-day pharmacology. Where possible, we highlight how commonly used drugs affect the circadian system.

A Network of (Autonomic) Clock Outputs

The circadian clock in the suprachiasmatic nuclei (SCN) is composed of thousands of oscillator neurons, each dependent on the cell-autonomous action of a defined set of circadian clock genes. A major question is still how these individual oscillators are organized into a biological clock that produces a coherent output capable of timing all the different daily changes in behavior and physiology. We investigated which anatomical connections and neurotransmitters are used by the biological clock to control the daily release pattern of a number of hormones. The picture that emerged shows projections contacting target neurons in the medial hypothalamus surrounding the SCN. The activity of these pre-autonomic and neuro-endocrine target neurons is controlled by differentially timed waves of vasopressin, GABA, and glutamate release from SCN terminals, among other factors. Together our data indicate that, with regard to the timing of their main release period within the LD cycle, at least four subpopulations of SCN neurons should be discernible. The different subgroups do not necessarily follow the phenotypic differences among SCN neurons. Thus, different subgroups can be found within neuron populations containing the same neurotransmitter. Remarkably, a similar distinction of four differentially timed subpopulations of SCN neurons was recently also discovered in experiments determining the temporal patterns of rhythmicity in individual SCN neurons by way of the electrophysiology or clock gene expression. Moreover, the specialization of the SCN may go as far as a single body structure, i.e., the SCN seems to contain neurons that specifically target the liver, pineal gland, and adrenal gland.

A Network of (Autonomic) Clock Outputs

The circadian clock in the suprachiasmatic nuclei (SCN) is composed of thousands of oscillator neurons, each of which is dependent on the cell-autonomous action of a defined set of circadian clock genes. A major question is still how these individual oscillators are organized into a biological clock producing a coherent output that is able to time all the different daily changes in behavior and physiology. We investigated which anatomical connections and neurotransmitters are used by the biological clock to control the daily release pattern of a number of hormones. The picture that emerged shows projections contacting target neurons in the medial hypothalamus surrounding the SCN. The activity of these pre-autonomic and neuro-endocrine target neurons is controlled by differentially timed waves of, among others, vasopressin, GABA, and glutamate release from SCN terminals. Together our data indicate that, with regard to the timing of their main release period within the light-dark (LD) cycle, at least 4 subpopulations of SCN neurons should be discerned. The different subgroups do not necessarily follow the phenotypic differences among SCN neurons. Thus, different subgroups can be found within neuron populations containing the same neurotransmitter. Remarkably, a similar distinction of 4 differentially timed subpopulations of SCN neurons was recently also discovered in experiments determining the temporal patterns of rhythmicity in individual SCN neurons by way of the electrophysiology or clock gene expression. Moreover, the specialization of the SCN may go as far as a single body structure; i.e., the SCN seems to contain neurons that specifically target the liver, pineal, and adrenal.

Vasopressin receptor V1a regulates circadian rhythms of locomotor activity and expression of clock-controlled genes in the suprachiasmatic nuclei

The suprachiasmatic nuclei (SCN) serve as the principal circadian pacemakers that coordinate daily cycles of behavior and physiology for mammals. A network of transcriptional and translational feedback loops underlies the operating molecular mechanism for circadian oscillation within the SCN neurons. It remains unclear how timing information is transmitted from SCN neurons to eventually evoke circadian rhythms. Intercellular communication between the SCN and its target neurons is critical for the generation of coherent circadian rhythms. At the molecular level, neuropeptides encoded by clock-controlled genes have been indicated as important output mediators. Arginine vasopressin (AVP) is the product of one such clock-controlled gene. Previous studies have demonstrated a circadian rhythm of AVP levels in the cerebrospinal fluid and the SCN. The physiological effects of AVP are mediated by three types of AVP receptors, designated as V1a, V1b, and V2. In this study, we report that V1a mRNA levels displayed a circadian rhythm in the SCN, peaking during night hours. The circadian rhythmicity of locomotor activities was significantly reduced in V1a-deficient (V1a(-/-)) mice (50-75% reduction in the power of fast Fourier transformation). However, the light masking and light-induced phase shift effects are intact in V1a(-/-) mice. Whereas the expression of clock core genes was unaltered, the circadian amplitude of prokineticin 2 (PK2) mRNA oscillation was attenuated in the SCN of V1a(-/-) mice ( approximately 50% reduction in the peak levels). In vitro experiments demonstrated that AVP, acting through V1a receptor, was able to enhance the transcriptional activity of the PK2 promoter. These studies thus indicate that AVP-V1a signaling plays an important role in the generation of overt circadian rhythms.

Comparative neuroanatomy of vasotocin and vasopressin in amphibians and other vertebrates

This review focuses on the neuroanatomical distribution of vasotocin (VT) and vasopressin (VP) and presents a comparative analysis of brain areas in which VT and VP cell bodies have been reported in fish, amphibians, reptiles, birds and mammals. A comparison of information from previous neuroanatomical studies of VT and VP with findings from a recent study of VT in an amphibian (Taricha granulosa) supports the conclusions that the VT/VP system can be subdivided into identifiable groups of cell bodies, based on neuroanatomical and cell morphology characteristics, and that these cell groups are not necessarily delimited by classical neuroanatomical boundaries. The comparative neuroanatomy of the distribution of VT and VP cell bodies also indicates that the neuroanatomy of the VT/VP system is fairly conserved among vertebrates. The review uses comparative data to present a series of tentative hypotheses about the homology of the VT cell groups and VP cell groups in the different vertebrate taxa.

Distribution of arginine-vasopressin in the trigeminal, dorsal root ganglia and spinal cord of the rat; depletion by capsaicin

We have measured arginine vasopressin in the neural lobe, the trigeminal ganglion (TG), dorsal root ganglia (DRG), spinal cord, trigeminal and sciatic nerves of the rat by radioimmunoassay. In control rats, the neural lobe contained 1600 pg/mg, the ganglia 52.5, 21.0, 8.5, 4.28, 3.85 pg/mg in the lumbar, sacral, cervical, thoracic, and trigeminal ganglion, respectively, the spinal cord contained 5.1, 4.3, 4.2 and 2.6 pg/mg in the lumbar, thoracic, sacral and cervical cord, respectively and the trigeminal and sciatic nerves contained 3.8 and 13 pg/mg. Neonatal capsaicin treatment depleted about 38-67% of AVP in the ganglia. Residual AVP amounted to 526.8, 30.55, 20.75, 12.88, 4.95, 2.74, 2.14, 7.94 and 2.53 pg/mg in the neural lobe, lumbar, thoracic, sacral, cervical DRG, lumbar, thoracic spinal cord, the sciatic and trigeminal nerves respectively. Capsaicin destroyed about 40.5% of total cells and 52% of AVP-immunoreactive neurons.

The role of intracellular messengers in adrenocorticotropin secretion in vitro

Adrenocorticotropin (ACTH), an opiomelanocortin peptide, is secreted from anterior pituitary corticotrophs upon stimulation with corticotropin-releasing hormone (CRH), arginine vasopressin (AVP) and several other neuropeptides. CRH, the most potent secretagogue of ACTH, stimulates ACTH secretion and biosynthesis by increasing the production of cyclic adenosine 3',5'-monophosphate (cAMP) within corticotrophs. AVP, which is a weak secretagogue of ACTH but strongly potentiates CRH-stimulated ACTH secretion, operates through the phosphatidylinositol (PI) transduction pathway. Both CRH and AVP increase cytosolic free [Ca2+] within normal corticotrophs indicating a role for Ca2+ in ACTH secretion. Glucocorticoids inhibit ACTH synthesis by suppressing transcription of the proopiomelanocortin (POMC) gene and attenuate ACTH release by decreasing cAMP accumulation stimulated by CRH. This review focuses on the roles of these intracellular messengers in ACTH secretion from normal anterior pituitary cells in vitro, and discusses the possible interactions between the cAMP, calcium and PI transduction pathways. Future areas of research are suggested such as identification of protein substrates of cAMP-dependent and Ca2(+)-dependent kinases within normal corticotrophs and evaluation of their role in ACTH biosynthesis and secretion.

Distribution and morphology of vasopressin-, neurophysin II-, and oxytocin-immunoreactive cell bodies in the forebrain of the cat

Experiments were done to provide a detailed map of the location and a description of morphological characteristics of vasopressin (AVP-IR)-, neurophysin II (NII-IR)- and oxytocin (OXY-IR)-immunoreactive neuronal perikarya in the forebrain of the cat. In addition, the location of cells in the forebrain retrogradely labeled following injections of tracers into the neurohypophysis was determined. The distribution of AVP-IR and NII-IR was similar in all cases studied. Most of the cells containing AVP-IR and OXY-IR were observed in the hypothalamic paraventricular (PVH) and supraoptic (SON) nuclei. In addition, AVP-IR and OXY-IR cell bodies were found in the regions of the nucleus of the diagonal band of Broca, the dorsal chiasmatic nucleus, the anterior hypothalamic-preoptic area, the periventricular area, the nucleus circularis, the perifornical area of the lateral hypothalamus, the accessory SON, the area of the tuber cinereum (Tca), and the medial nucleus of the amygdala. The density of AVP-IR cells was greater than that of OXY-IR cells in these regions. Several forebrain areas were also observed to contain only AVP-IR perikarya: the suprachiasmatic nucleus (Sc), the bed nucleus of the stria terminalis, and the region of the substantia innominata and ventral globus pallidus (SI/GP). In addition, the dorsomedial nucleus of the hypothalamus only contained OXY-IR perikarya. Most of the cells immunoreactive to AVP were multipolar and had spinelike processes over their somata and proximal dendrites. In addition, the majority of cells in the PVH and SON were round or oval, whereas those outside these nuclei were fusiform or triangular. The mean somal area of AVP-IR cells in the region of the SI/GP was significantly (P less than 0.05) larger than that of AVP-IR cells in all other regions examined, whereas the mean somal area of Sc AVP-IR cells was significantly (P less than 0.05) smaller than that of all other groups of AVP-IR cells examined. Most OXY-IR cells were similar morphologically to those immunoreactive to AVP, except that OXY-IR cell bodies and their appendages did not have spinelike processes. In addition, OXY-IR perikarya were generally of uniform size. OXY-IR cells in the PVH and accessory SON were significantly (P less than 0.05) larger than AVP-IR cells in the same regions, but were not different from AVP-IR cells in the lateral hypothalamus and SON.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of salt loading and salt deprivation on the vasopressin and oxytocin content of the median eminence and the neural lobe in adrenalectomized rats

In adrenalectomized rats the influence of salt loading or salt deprivation on the vasopressin and oxytocin content of the median eminence (ME) and the neural lobe (NL) was studied by means of various methods: morphometric and microphotometric analysis of aldehyde fuchsin-stained sections of ME and NL; immunohistochemical demonstration of neurophysin, oxytocin, and vasopressin in the ME and in the NL; radioimmunological measurement of oxytocin and vasopressin in the ME and in the NL. Adrenalectomy in salt-substituted rats raised the vasopressin content of the outer layer of the ME (OLME) but had no influence on the amount of vasopressin in the inner layer of the ME and in the NL. Osmotic stimulation of adrenalectomized rats by hypertonic saline markedly diminished vasopressin and oxytocin in the inner layer of the ME and in the NL but did not, or only slightly reduced vasopressin in the OLME. Withdrawal of salt supplementation in adrenalectomized rats resulted in a decrease of plasma sodium and plasma volume. It did not change the vasopressin or oxytocin content of the inner layer of the ME and of the NL, but it was correlated with a decrease of vasopressin in the OLME. The present findings may suggest that vasopressin in the OLME is involved in salt and/or volume regulation by influencing the hypophysial-adrenal axis.

Morphological changes of rat neurosecretory neurones after stereotaxic injection of kainic acid into the supraoptic nucleus or the supraoptico-hypophyseal tract

Kainic acid is a structural analogue of glutamic acid possessing neurotoxic property. In the present study, performed on rats, morphological changes of neurosecretory neurones after stereotaxic injection of kainic acid into the left supraoptic nucleus or into the left supraoptico-hypophyseal tract were investigated. It is shown that administration of kainic acid in a dose that leads to destruction of hippocampal pyramidal cells has no effects on supraoptic perikarya but does destroy neurosecretory axons. These results contradict the observations of many authors who reported that local injection of kainic acid into the brain causes degeneration of perikarya but leaves axons of passage unaffected.

A quantitative and morphometric evaluation of 125I-alpha-bungarotoxin binding in the rat hypothalamus

The distribution of 125I-alpha-bungarotoxin (alpha-BTX), a putative nicotinic cholinergic receptor ligand was studied both in vitro and in vivo in the suprachiasmatic nucleus (SCN), anterior hypothalamic area (AHA), and supraoptic nucleus (SON) of the hypothalamus. For in vitro studies 20 micron frozen frontal sections containing SCN were incubated with either radioligand or, unlabeled alpha-BTX plus 125I alpha-BTX and tissues were processed for light microscopic autoradiography. Areas of cresyl violet stained SCN sections were measured using a Bioquant Analysis System and grain counts and distributions were determined. For in vivo investigations third ventricular infusion of either 125I alpha-BTX, or unlabeled alpha-BTX with 125I alpha-BTX was performed, and 24 hours later animals were perfused pericardially and 1 micron serial plastic sections of the SCN were processed for light microscopic autoradiography. Localization of silver grains in 1 micron serial sections was evaluated in a double blind study. In vitro and in vivo labeling patterns in the hypothalamus were the same and compared well with previously examined paraffin-processed tissues from animals which had received third ventricular infusions of the neurotoxin. We observed a distinctive and specific labeling pattern of the SCN. Grains tended to localize diffusely and uniformly in more rostral regions, but clustered densely in the dorsal and lateral mid-SCN, and dorsally in the mid-caudal SCN. Grains were localized in the SCN where larger neurons were found. In the most caudal regions of the SCN no labeling was observed. Tissues from unlabeled alpha-BTX plus 125I alpha-BTX in vitro or in vivo studies did not demonstrate grain counts above background levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Intragranular colocalization of CRF and Met-Enk-8 in nerve terminals in the rat median eminence

The ultrastructural localizations of rat corticoliberin (rCRF) and methionine-enkephalin octapeptide (Met-Enk-8) in the external layer of the rat median eminence were examined by double-immunogold labeling with anti-rCRF and anti-Met-Enk-8 sera labeled with small-sized (Gs) and medium-sized (Gm) gold particles, respectively. Two types of immunolabeled terminals were distinguished: one type with small granules (70 nm) labeled with Gs, and the other with large granules (100 nm) labeled with Gm. In both types, however, some granules were labeled with both Gs and Gm.

Co-localization of corticotropin-releasing factor and vasopressin in median eminence neurosecretory vesicles

Vasopressin (VP) potentiates the effect of corticotropin-releasing factor (CRF) on the secretion of adrenocorticotropic hormone (ACTH) from anterior pituitary cells in vitro, and both CRF and VP have been found in portal blood. These data support the hypothesis that VP acts synergistically with CRF to cause the secretion of ACTH in vivo but the origin of the CRF and VP, and the physiology of their release, have not been precisely defined. Parvocellular cell bodies in the paraventricular nucleus (PVN) which project to the external zone of the median eminence can be stained for both CRF and VP after adrenalectomy, and there is light microscopic immunocytochemical evidence that neurophysin (NP) may be located within some of the CRF-containing axons. Electron microscopic immunocytochemical studies have demonstrated the presence of CRF, VP and its 'carrier' protein, VP-associated neurophysin (NP-VP) in 100-nm neurosecretory vesicles (NSVs) in axons terminating near the portal capillary plexus in the external zone of the median eminence. If these peptides are extensively co-localized in the same NSVs in the median eminence, then coordinate secretion of CRF and VP in vivo is obligatory, at least in some physiological circumstances. We demonstrate in this report, using post-embedding electron microscopic immunocytochemistry on serial ultrathin sections, that CRF, VP and NP-VP are contained not only in the same axons and terminals, but in the same 100-nm NSVs in the median eminence of both normal and adrenalectomized rats. In addition, in the normal rat median eminence 44% of the CRF-positive axons and terminals stained strongly for VP and NP-VP, whereas in the adrenalectomized rat virtually all the CRF-positive structures in the median eminence showed strong staining for VP and NP-VP, indicating a transformation of one subpopulation of CRF-positive axons and terminals by adrenalectomy.

Neurotransmitters of the hypothalamic suprachiasmatic nucleus: immunocytochemical analysis of 25 neuronal antigens

An immunocytochemical analysis with 33 antisera was undertaken to investigate the localization of 25 different neurotransmitter-related antigens in the hypothalamic suprachiasmatic nucleus in the rat. To obtain estimates of relative densities of immunoreactive axons a stereological approach was used involving counting of intersections of immunoreactive axons with a superimposed semi-circle test grid. All neurotransmitter-related antigens found in perikarya within the suprachiasmatic nucleus, including those stained with antisera against bombesin, gastrin-releasing peptide, neurophysin, vasopressin, somatostatin, gamma-aminobutyrate, glutamate decarboxylase and vasoactive intestinal polypeptide were also found in axons within the nucleus. A greater number of these immunoreactive axons was found within the nucleus than in the adjacent anterior hypothalamus. The size of all immunoreactive axons in the suprachiasmatic nucleus was consistently small; immunoreactive axons were found ramifying widely in the nucleus, often ending with terminal boutons near perikarya immunoreactive for the same antigen. All neurotransmitter-related substances found in perikarya of the suprachiasmatic nucleus were also found in axons crossing over the midline to innervate the contralateral nucleus, providing an anatomical substrate for a high degree of communication between the paired nuclei. Axons immunoreactive for other putative transmitters including serotonin arising outside the nucleus were also found in high densities within the nucleus and crossing over the midline between the nuclei. Immunoreactivity for some transmitters was found in axons of similar densities within and outside the nucleus, including antisera against tyrosine hydroxylase; a small number of dopamine beta-hydroxylase and a few phenylethanolamine N-methyltransferase-immunoreactive axons were found in the SCN, suggesting that dopamine, norepinephrine and epinephrine may occur in a limited number of axons in the nucleus. Small numbers of axons immunoreactive with antisera raised against cholecystokinin, prolactin, substance P, thyrotropin-releasing hormone and choline acetyltransferase were found within the suprachiasmatic nucleus. Axons immunoreactive for luteinizing hormone-releasing hormone, adrenocorticotropic hormone, alpha-melanocyte-stimulating hormone and neurotensin were rarely found within the suprachiasmatic nucleus; axons immunoreactive for luteinizing hormone-releasing hormone, adrenocorticotropic hormone, cholecystokinin and tyrosine hydroxylase were found in both horizontal and coronal sections in the area between the left and right suprachiasmatic nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution of neurophysin II immunoreactive nerve fibers within the subnuclei of the nucleus of the tractus solitarius of the rat

The location of neurophysin II immunoreactive nerve fibers and preterminal processes has been examined in various functionally distinct subnuclei of the nucleus of the tractus solitarius (nTS) using the indirect immunofluorescence method for immunocytochemistry combined with cytoarchitectonic identification. The nTS is responsible for integrating respiratory and autonomic reflex activity: the vlnTS, vnTS, ni and nI are associated with respiratory activity; the dlnTS and dnTS are important sites for the integration of baroreceptor and chemoreceptor activity; the ncom, dnTS and dlnTS integrate cardiac afferent activity and the mnTS mediates both cardiovascular and gastrointestinal effects. At levels caudal to the obex, the ncom contained the largest number of neurophysin II immunoreactive nerve fibers and the mnTS and dmnX contained moderate neurophysin II immunoreactivity. At levels rostral to the obex the region of the dorsal medulla adjacent to the mnTS and dnTS (PVR and dPSR) showed the densest immunoreactivity and the mnTS, dmnX and vPSR showed moderate immunoreactivity. At the rostral pole of the nTS, neurophysin II immunoreactive nerve terminals were seen in the dendritic regions of cells in dmnX and mnTS. This selective distribution of neurophysin II immunoreactive nerve terminals in the cardiovascular and gastrointestinal subnuclei of the nTS implicates a direct, descending, hypothalamic, oxytocin-neurophysin II containing pathway interacting with these nTS functions. These results confirm the hypothesis (Sawchenko and Swanson) that descending neurophysin II immunoreactive pathways represent an important neuronal system for the hypothalamic regulation of cardiovascular (vasomotor) and gastrointestinal nuclei in the brainstem.

The organization of noradrenergic pathways from the brainstem to the paraventricular and supraoptic nuclei in the rat

Axonal transport and immunohistochemical methods have been used to clarify the organization of pathways from noradrenergic and adrenergic cell groups in the brainstem to the paraventricular (PVH) and supraoptic (SO) nuclei of the hypothalamus. First, the location of such cells was determined with a combined retrograde tracer-immunofluorescence method. The fluorescent tracer, True Blue, was injected into the PVH or the SO, and sections through the brainstem were stained with anti-(rat) DBH, a specific marker for noradrenergic and adrenergic neurons. It was found that, after injections in the PVH, doubly labeled neurons were confined almost exclusively to 3 cell groups, the A1 region of the ventral medulla, which contained a majority of such cells, the A2 region in the dorsal vagal complex, and the locus coeruleus (A6 region). After injections centered in the SO an even greater proportion of doubly labeled cells were found in the A1 region, although some were also found in the A2 and A6 regions. The topography of doubly labeled cells indicates that these projections arise primarily from noradrenergic neurons, although adrenergic cells in both the C1 and the C2 groups probably contribute as well. Because well over 80% of the retrogradely labeled cells in these three regions were also DBH-positive, we next placed injections of [3H]amino acids into each of them in different groups of animals, and traced the course and distribution of the ascending (presumably DBH-positive) projections to the PVH and SO in the resulting autoradiograms. Injections centered in the A1 region labeled a substantial projection to most parts of the parvocellular division of the PVH, and was most dense in the dorsal and medial parts. In addition, terminal fields were labeled on those parts of the magnocellular division of the PVH, and of the SO, in which vasopressinergic cell bodies are concentrated. Injections centered in the A2 region also labeled a projection to the parvocellular division of the PVH that was topographically similar, but less dense, than that from the A1 region. In contrast, [3H]amino acid injections centered in the locus coeruleus labeled a moderately dense projection to the PVH that was limited to the medialmost part of the parvocellular division. Neither the A2 nor the A6 cell groups project to the magnocellular parts of PVH, or to the SO. The autoradiographic material, and additional double-labeling experiments, were used to identify and to characterize projections that interconnect the A1, A2 and A6 regions, as well as possible projections from these cell groups to the spinal cord. These results may be summarized as follows: a substantial projection from the nucleus of the solitary tract to the A1 region was identified, but this pathway does not arise from catecholaminergic neurons in the A2 cell group. DBH-stained cells in the A1 region project back to the dorsal vagal complex, as well as quite massively to the locus coeruleus (A6 region)...

The tuberoinfundibular system of the rat as demonstrated by immunohistochemical localization of retrogradely transported wheat germ agglutinin (WGA) from the median eminence

The origin of neuronal perikarya which project to the external zone of the median eminence (the tuberoinfundibular neuronal system) was determined in the rat after injection or diffusion of wheat germ agglutinin (WGA) into the median eminence. The retrogradely transported lectin was detected in neurons using an immunohistochemical method based on the peroxidase-antiperoxidase technique. Immunoreactive cell bodies were found both in hypothalamic and extrahypothalamic regions. Within the hypothalamus, the majority of peroxidase-positive cells were present in the dorsomedial and basolateral portions of the arcuate nucleus, regions of the periventricular nucleus, and the preoptic region, particularly at the level of the organum vasculosum of the lamina terminalis (OVLT). Within the extrahypothalamic regions, WGA-positive perikarya were found in the diagonal band of Broca, the region of the medical septum and the brainstem. Only rare cells were labeled in the ventromedial nucleus of the hypothalamus and no cells were labeled in any region of the amygdala. These data demonstrate that neurons with afferent projections to the median eminence are more widely distributed in the rat brain than previously recognized and therefore, that the concept of the tuberoinfundibular neuronal system must be expanded.

Terminal degeneration in the lateral septum of the rat after suprachiasmatic nucleus lesion

Nerve terminals in the lateral septum were studied by electron microscopy in the rat after lesions of the suprachiasmatic nuclei (SCN). The results were as follows: 1) The electron-lucent degenerations showed a reduction in the number of vesicles and the swelling of terminals and/or vesicles. These degenerating terminals predominated at two days of survival period. The electron-dense degenerations which showed a darkening and shrinkage of the terminals mainly appeared at four days of survival period. 2) Most of the degenerating terminals contained large core vesicles of a diameter in the range of 800-1500 A. 3) The percentage of the degenerating terminals to all the terminals on the electron micrographs was about 7%. 4) The F-type synapses were not found in the lateral septum of the normal and SCN lesion rats. These data confirmed the existence of the projection which reached the lateral septum from the SCN and suggested to us that these synapses were so-called peptidergic synapses.

Identification of parvocellular vasopressin and neurophysin neurons in the suprachiasmatic nucleus of a variety of mammals including primates

The presence of parvocellular vasopressin- and neurophysin-containing neurons in the suprachiasmatic nucleus (SCN) was investigated in 13 mammalian species representing six mammalian orders (marsupials, rodents, lagomorphs, artiodactyls, carnivores, and primates), using specific antisera to vasopressin and neurophysin in the unlabelled antibody=enzyme immunoperoxidase method. In all mammals examined, including man, parvocellular vasopressin and neurophysin neurons were found in the SCN. Only a portion of SCN neurons contain vasopressin and neurophysin, the number varying with species. Cell counts comparing the number of immunoreactive to Nissl-stained neurons showed averages of 17% immunopositive neurons in the rat SCN, and 31% in the human SCN. No oxytocin-containing SCN neurons were observed. These findings suggest that parvocellular vasopressin and neurophysin neurons are widely represented in mammals.

Synthesis, transport, and release of posterior pituitary hormones

Vasopressin and oxytocin are made and released by neurons of the hypothalamo-neurohypophysial system. Pulse labeling these neurons with radioactive amino acid indicates that the two hormones and their respective neurophysin carrier proteins are synthesized as parts of separate precursor proteins. The precursors seem to be processed into smaller, biologically active molecules while they are being transported along the axon.

Infundibular localization of vasopressin, oxytocin and neurophysins in the rat; its relationships with corticotrope function

The distribution of vasopressin (VP), oxytocin (OXY) and neurophysins 1 and 2 (N1, N2) has been studied in the median eminence (ME) of normal, heterozygous (HDI) and Brattleboro (DI) rats. Numerous thin periportal VP and N2 fibres exist in the normal and HD1 rats; they have never been observed in the DI rats. N1 and OXY fibres in the external layer of the median eminence are rare. Adrenalectomy increases periportal VP and N2 loading in normal and HDI rats; it does not modify the appearance of the DI median eminence. Dexamethasone prevents external VP and N2 overloading in adrenalectomized rats injected during the whole postoperative period. Injections of vasopressin indicated that it had a negative feedback effect during a short time (3 days) but not during a longer period (7 days). The suprachiasmatic neurons are stained only by anti-VP and anti-N2 antibodies. Their overstaining induced by adrenalectomy disappears with dexamethasone, aldosterone or vasopressin treatment. This central effect of hormones is not necessarily associated with disappearance of overloading in the external layer of the ME. The hypothalamo-infundibular tract carrying VP and N2 is involved in regulatory mechanisms of the corticotrope axis. Its relationships with suprachiasmatic neurons are discussed.

Detection of aldehydefuchsin-positive neurosecretory granules in the cells of the suprachiasmatic nucleus of the rat

Application of dark field microscopy to sections fixed with picric acid--formalin and stained with crotonaldehydefuchsin allows the demonstration of neurosecretory granules in the neurones of the suprachiasmatic nuclei of normal rats.

Identification of vasopressin in the subfornical organ region: effects of dehydration

The subfornical organ (SFO), a neuroendocrine structure implicated in saltwater homeostasis, contains secretory structures histochemically similar to those in the neurohypophysis. Because of these morphological similarities, we compared levels of vasopressin (vp) in the SFO area and the adjacent hippocampal commissure-fornix (HC-F) of normally hydrated and 48 h water-deprived (WD) rats. VP in the SFO region from normally hydrated rats was 44 +/- 5 pg/mg protein, 3.5 +/- 0.4 ng/g wet weight or 3.6 +/- 0.4 pg/SFO. These concentrations increased (P less than 0.05) about twofold after WD. The content of VP, ng/g wet weight, in HC-F was higher (P less than 0.05) than the SFO area and also increased (P less than 0.05) after WD. VP was detected in other fiber tracts, anterior commissure (AC) and fornix (F), but was unchanged by WD. Changes in hormone observed in the SFO and HC-F regions were therefore not part of a generalized increase of VP in the brain, nor can they be ascribed to elevated plasma levels. Thus, VP changes in the SFO region may be functionally significant and related to an SFO endocrine role in hydration. VP in fiber tracts (F, AC) unassociated with the hypothalamo-hypophysial system and unchanged after WD may suggest an unidentified role of this hormone in the central nervous system.

Immunocytochemical localization of the vasopressinergic and the oxytocinergic neurons in the human hypothalamus

The human hypothalamic-neurohypophysial hormone-producing nuclei were investigated with the unlabeled antibody peroxidase-antiperoxidase complex (PAP) technique at the light microscopic level. The size, shape and location of the supraoptic, paraventricular, accessory supraoptic and suprachiasmatic nuclei were determined. It was demonstrated in the human hypothalamus, as well as in the hypothalamus of other mammals, that vasopressin and oxytocin are synthesized in separate neurons. In each of the nuclei of the magnocellular neurosecretory system, the distribution, ratios and structural features of the vasopressinergic and oxytocinergic neurons were determined. It was shown that the human suprachiasmatic nuclei contain numerous neurophysin-vasopressin-producing neurons.

Effect of fixation on the demonstration of neurophysin and "Gomori-positive" substances in neurosecretory granules of the rat hypothalamus

Proteins reacting with neurophysin antibodies and "Gomori-positive" substances were demonstrated histochemically in hypothalamic neurosecretory material of normal and bilaterally adrenalectomized rats after two different fixations: a) picric acid-formalin (PAF) for 7 days at 37 degrees C; b) Bouin's fluid for 20 h at 4 degrees C. After PAF-fixation anti-neurophysin reactive neurosecretory granules are found in all parts of the supraoptico-hypophysial system and in the suprachiasmatic nucleus of normal and adrenalectomized animals. In the latter they can additionally be demonstrated in the outer layer of the median eminence. Amount and distribution of "Gomori-positive" substances correspond to those described for the immunoreactive material, except for the suprachiasmatic nucleus, in which the substances can not be detected; Following fixation in Bouin's fluid the immunohistochemical reactions are unchanged whereas the staining of "Gomori-positive" substances is remarkably impaired. The amounts of the substances demonstrable in the neural lobe are diminished and in the cells of the supraoptic and paraventricular nuclei as well as in both median eminence layers only traces of the substances are to be seen. The findings indicate that negative results in demonstrating "Gomori-positive" substances may be caused by inappropriate fixation and need to be controlled by immunohistochemical techniques.

Catecholamine turnover alterations in discrete areas of the median eminence of the 4- and 5-day cyclic rat

Using quantitative microfluorimetry in combination with tyrosine hydroxylase inhibition (H44/68) the concentration and turnover of noradrenaline (NA) and dopamine (DA) was studied in the subependymal layer (SEL) and the medial (MPZ) and lateral palisade zone (LPZ) of the rat median eminence during the 4- and 5- day vaginal estrous cycle. Significant cyclic variations were only found in SEL and LPZ. The NA turnover in SEL was high on proestrous and low on all other days of the 4-day estrous cycle, whereas in the 5-day estrous cycle the NA turnover in SEL started to increase already on the second day of diestrous to reach a peak in the afternoon of proestrous. At that time also the NA concentrations in SEL were increased, although significantly only in the 5-day cyclic rats. The DA turnover in LPZ was low on proestrous and high on all other days in both 4-and 5-day cyclic rats. Apart from the median eminence cyclic variations in catecholamine metabolism were only found in the medial preoptic area, where NA turnover was high on proestrous and low on estrous-diestrous. The present findings give further support for the existence of a facilitatory noradrenergic and inhibitory dopaminergic mechanism in the control of gonadotrophin release. Furthermore, it is suggested that an acceleration of reticulo-hypothalamic NA turnover precedes the retardation of tubero-infundibular DA turnover found on proestrous and that the time lag between initial NA activation and subsequent DA inactivation is longer in the 5-than in the 4-day estrous cycle.

Hyperplasia of "pancreatic polypeptide"-cells in the pancreas of juvenile diabetics

The cellular composition of the pancreatic islets of juvenile diabetics was studied, using recently developed immunocytochemical methods. B-cells were identified only in juvenile diabetics with a disease of short duration. In chronic juvenile diabetics, the islets which are classically viewed as "atrophic", were shown to be composed of glucagon- and of somatostatin-cells. Another type of islets which commonly occurs in the pancreas of juvenile diabetics, i.e. the ribbon-like type first described by Cecil in 1911, appeared to be composed almost exclusively of "pancreatic polypeptide" (HPP)-cells. It is suggested that hyperplasia of the HPP-cells in the pancreas of juvenile diabetics results from an atypical type of islet regeneration induced by a severe and prolonged injury to the pancreatic endocrine tissue.

Electron microscope immunohistochemical localization of neurophysin in the rat with hereditary diabetes insipidus

In order to study the subcellular distribution of neurophysin in the rat with hypothalamic hereditary diabetes insipidus (DI), an immunoelectron microscopic localization of neurophysin was performed in the hypothalamo-neurohypophysial system of both homozygous and heterozygous DI rats. Whereas in control rats neurophysin was localized in the granules present in the secretory neurons, in the homozygous DI rats neurophysin was found in the granules and outside the granules in the perikarya and axons of neurons of both supraoptic and paraventricular nuclei. In the heterozygous DI rats findings similar to those observed in homozygous DI rats were observed, although in the posterior pituitary, the exgranular material appeared to be less abundant than in homozygous DI rats. These results clearly demonstrated that in hyperstimulated neurons neurophysin was distributed in both granular and extragranular compartments.

Ultrastructural immunohistochemical localization of vasopressin in the hypothalamic-neurohypophysial system of three murids

Vasopressin was immunohistochemically localized at the electron microscopic (EM) level in the hypothalamic-neurohypophysial system (HNS) of three murids. Antiserum to vasopressin was produced in rabbits injected with lysine vasopressin (LVP) conjugated to egg albumin (EA), anti-EA being precipitated prior to staining. Sternberger's unlabeled antibody peroxidase technique was employed, immunoreactivity being designated by peroxidase-anti-peroxidase (PAP) molecules and electron opacity. Immunoreactive neurosecretory granules (NSG) were found in the perikarya of the supraoptic nucleus (SON) in all three murids investigated, although far more profusely in the two wild strains. Immunoreactive axonal NSG were observed in the inner and outer zones of the median eminence (ME), and within most of the axons and terminals in the neurohypophysis. The concentration of primary serum effective for staining the SON (1:10-1:50) was far higher than that required for the ME and the neurohypophysis (1:500-1:1,200). Anti-LVP also induced electron opacity of granules in cells of the pars intermedia (PI). Discussion centers of the significance of immunoreactive NSG in the neurosecretory (NS) perikarya, on the possibility of an extragranular pool of hormone, and on speculation about the electron opacity of the PI granules.