Estrogen receptor beta and G protein-coupled estrogen receptor 1 are involved in the acute estrogenic regulation of arginine-vasopressin immunoreactive levels in the supraoptic and paraventricular hypothalamic nuclei of female rats.

The ovarian hormone 17ß-estradiol is known to regulate the release, expression and immunoreactivity of arginine-vasopressin (AVP) in the supraoptic and paraventricular hypothalamic nuclei of rodents. Previous studies have shown that estrogen receptor α is involved in the effects of chronic estradiol administration on arginine-vasopressin immunoreactivity in the female rat hypothalamus. In this study we have examined the effect of an acute administration of estradiol or specific agonists for estrogen receptors α, ß and G protein-coupled estrogen receptor 1 on the immunoreactivity of arginine-vasopressin in the hypothalamus of adult ovariectomized female rats. Acute estradiol administration resulted in a significant decrease in the number of arginine-vasopressin immunoreactive neurons in the supraoptic and paraventricular nuclei after 24 h. The effects of the specific estrogen receptors agonists suggest that the action of estradiol on arginine-vasopressin immunoreactivity is mediated in the supraoptic nucleus by G protein-coupled estrogen receptor 1 and in the paraventricular nucleus by both estrogen receptor ß and G protein-coupled estrogen receptor 1. Thus, in contrast to previous studies on the effect of chronic estrogenic treatments, the present findings suggest that estrogen receptor ß and G protein-coupled estrogen receptor 1 mediate the acute effects of estradiol on arginine-vasopressin immunoreactivity in the hypothalamus of ovariectomized rats.

Inhibition of heme oxygenase in the central nervous system potentiates endotoxin-induced vasopressin release in the rat.

Previous in vitro studies have shown that increases in endogenous carbon monoxide (CO) generation via activation of the enzyme heme oxygenase (HO) within the rat hypothalamus are associated with the reduced release of the neuropeptides, vasopressin (AVP) and oxytocin, while evidence concerning corticotrophin-releasing hormone (CRH) is controversial. The present study investigated whether there is also a functional relationship between the HO-CO pathway and AVP and corticosterone (Cort) in vivo. Male Wistar rats were challenged with bacterial lipopolysaccharide (LPS) at doses producing significant activation of the hypothalamo-pituitary-adrenal (HPA) axis. LPS was given alone or after pretreatment with the HO inhibitor Sn-protoporphyrin-9 (SnPP9). The latter was injected either intraperitoneally (i.p.) or by intracerebroventricular (i.c.v.) route. SnPP9 given i.p. failed to modify either basal or LPS-stimulated levels of AVP and Cort. On the contrary, i.c.v. SnPP9 strongly potentiated LPS-induced AVP release and significantly enhanced basal serum Cort levels, although it failed to potentiate stimulation by LPS. The LPS + i.c.v. SnPP9 also significantly reduced the hypothalamic stores of AVP compared to controls, correlating with increased circulating levels of AVP. Taken collectively, these data are in concordance with previous in vitro observations showing that the HO-CO pathway acts centrally to attenuate endotoxin-stimulated AVP release, while having less effects on the pituitary-adrenal axis.

[The effect of electroacupuncture on the discharge activity of temperature-sensitive neurons of preoptic-anterior hypothalamus in the rabbit treated by arginine vasopressin].

Arginine vasopressin (AVP) has been shown to have significant effects on the thermoregulation. The present experiments were to investigate the effect of electroacupuncture (EA) on the discharge activity of temperature-sensitive neurons of preoptic-anterior hypothalamus (PO-AH) in rabbits treated by AVP and arginine vasopressin monoclonal antibody (AVPMcAb). The results were as follows: (1) AVP could markedly promote the firing activity of EA on heat-sensitive neurons in PO-AH. (2) AVPMcAb could markedly reduce the effect of EA on temperature-sensitive neurons in PO-AH. Experimental results indicated that the mechanisms of EA on hypothermia might be related to AVP.

Ontogeny and molecular weight of immunoreactive arginine vasopressin and corticotropin-releasing factor in the ovine fetal hypothalamus.

In sheep, arginine vasopressin (AVP) and corticotropin-releasing factor (CRF) stimulate adrenocorticotropic hormone (ACTH) secretion. Increased hypothalamic secretion of these peptides at the end of gestation initiates parturition in this species. We hypothesized that CRF and/or AVP content in the fetal hypothalamus increases late in gestation and that this content was comprised of multiple molecular weight forms of these peptides. Hypothalami and pituitaries were collected from fetuses and lambs (74 days' gestation to 4 weeks postnatal). Hypothalamic concentrations of immunoreactive AVP (IR-AVP) and CRF (IR-CRF) significantly increased during late fetal and neonatal development (p < 0.01). Pituitary AVP concentration did not change. Western blot and gel exclusion chromatography revealed both processed and precursor forms of IR-CRF and IR-AVP in the hypothalamus. We conclude that ovine fetal and neonatal hypothalami contain both processed and unprocessed forms of IR-CRF and IR-AVP and that, overall, concentrations of the immunoreactive peptides increase over the course of development.

Increased number of corticotropin-releasing hormone expressing neurons in the hypothalamic paraventricular nucleus of patients with multiple sclerosis.

Observations in experimental allergic encephalomyelitis (EAE), a model for multiple sclerosis (MS), have indicated that a low activity of the hypothalamo-pituitary-adrenal (HPA) system is accompanied by a high susceptibility for EAE in rat strains and that elevated corticosteroid levels are necessary for spontaneous recovery from EAE. The HPA axis activity is regulated by both corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP). Both types of neurons are localized in the paraventricular nucleus (PVN) of the hypothalamus. We determined the number of immunocytochemically identified CRH-immunoreactive (CRH-IR) and AVP-immunoreactive (AVP-IR) neurons in the PVN of the human hypothalamus of 8 MS patients, aged 34-63 years, and 8 age-matched control subjects without any primary neurological or psychiatric disorders, aged 30-59 years. In addition, the number of oxytocin (OXT) immunoreactive (OXT-IR) neurons was determined, since these neurons innervate brain stem nuclei and might thus be related to autonomic disturbances in MS. In MS the staining intensity for AVP was clearly lower and for OXT slightly lower. For CRH, the staining intensity was similar in both groups, and, moreover, in MS patients the number of CRH-IR cells in the PVN was found to be about 2.4 times higher than that in the control group. The number of OXT-IR or AVP-IR cells in the PVN of MS patients was not significantly different from that of the control group. Our results point to an activation of the neuroendocrine HPA axis which may be compatible with the idea that the HPA axis is involved in recovery from MS.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo evidence that arginine vasopressin is involved in the adrenocorticotropin response induced by interleukin-6 but not by tumor necrosis factor-alpha in the rat.

We examined whether arginine vasopressin (AVP) is involved in the adrenocorticotropin (ACTH) response induced by interleukin (IL)-6 or tumor necrosis factor (TNF)-alpha in the rat. To accomplish this, we employed immunoneutralization of brain AVP by injecting anti-AVP antiserum intracerebroventricularly (i.c.v., 3rd ventricle). For comparison, we also tested the effect of immunoneutralization of corticotropin-releasing hormone (CRH) in the brain. Anti-CRH antibody, anti-AVP antibody, or normal rabbit serum (control) was given i.c.v. 15 min before an i.c.v. administration of human recombinant IL-6 (100 ng) or TNF-alpha (100 ng). Both IL-6 and TNF-alpha significantly elevated plasma ACTH levels. The IL-6-induced ACTH response was significantly suppressed by both anti-CRH and anti-AVP antibodies. On the other hand, the TNF-alpha-induced ACTH response was not significantly affected by anti-AVP antibody, although anti-CRH antibody could suppress the response. These results suggest that the IL-6-induced ACTH response may be mediated by both CRH and AVP, whereas the ACTH response to TNF-alpha is only via CRH.

The role of arginine vasopressin in interleukin-1 beta-induced adrenocorticotropin secretion in the rat.

In this study we examined whether arginine vasopressin (AVP) in the brain is involved in the adrenocorticotropin (ACTH) secretion induced by interleukin (IL)-1 beta in the rat. Human recombinant IL-1 beta (50 ng) was given intracerebroventricularly to freely moving male rats with or without a prior (15 min before) administration of anticorticotropin releasing hormone (CRH) or AVP antibody via the same route. The ACTH response to IL-1 beta was significantly reduced by both anti-CRH and anti-AVP antisera compared to the levels after normal rabbit serum. These results suggest that not only CRH but also AVP may mediate the IL-1 beta stimulation of ACTH secretion in the rat.

Detection of vasopressin cell antibodies in some patients with autoimmune endocrine diseases without overt diabetes insipidus.

OBJECTIVE: Cytoplasmic autoantibodies to vasopressin cells (AVP) have been detected in patients with idiopathic central diabetes insipidus and only in one patient with endocrine autoimmune diseases without clinical diabetes insipidus. The aim of this study was to look for AVP cell antibodies (AVP-cell-Ab) in human sera of a large population of autoimmune endocrine disease patients without diabetes insipidus and to test whether an occurrence of these antibodies in some patients can be associated with partial impairment of posterior pituitary function. MEASUREMENT: Sera from 410 patients (310 females, 100 males, age range 10-46 years) with autoimmune endocrine disorders (260 with thyroid autoimmune disease, and 150 with insulin dependent diabetes mellitus) without clinical diabetes insipidus, and from 100 normal subjects, were investigated for hypothalamic autoantibodies by an indirect immunofluorescence method. Positive sera were subsequently tested with specific rabbit anti AVP serum. RESULTS: None of controls, but five out of 410 patients (1.2%) were AVP-cell-Ab positive. All positive and nine negative from the 410 screened patients were tested for posterior pituitary function. Two out of five AVP-cell-Ab positive patients showed partial diabetes insipidus. CONCLUSION: AVP cell antibodies can be shown in some patients with endocrine autoimmune disease without diabetes insipidus and can sometimes be associated with findings of partial posterior pituitary dysfunction. This suggests that clinical diabetes insipidus could be preceded by a long subclinical period characterized only by the occurrence of AVP-cell-Ab in the sera associated or followed by alterations in functional tests. Longitudinal studies are needed to confirm this hypothesis.

Sexual differences in the magnocellular vasopressinergic system in golden hamsters.

Golden hamsters, as compared to rats, lack several parvicellular vasopressinergic cell groups, particularly sexually dimorphic populations. We decided to test the possibility that magnocellular vasopressinergic neurons are subjected to sexual differences in hamsters, as they are known to display vasopressin (AVP)-dependent sexually dimorphic behaviors. The distribution of magnocellular vasopressinergic neurons was mapped and compared between males and females. Approximately 50% more vasopressin-immunoreactive (AVP-ir) neurons were counted in males within the medial and lateral divisions of the supraoptic nucleus. Furthermore, levels of AVP extracted from the hypothalamus and the pituitary gland were three to four times higher in males than in females. Finally, hypothalamic extracts from a male and a female hypothalamus were fractionated by HPLC and assayed for AVP immunoreactivity. Immunoreactivity from each extract had the same retention time as synthetic AVP standards; and the levels were twice as high in the male. These results support the existence of sexual differences in the magnocellular vasopressinergic system in golden hamsters. These differences appear to be related to previously reported sexual differences in AVP secretion from the neurohypophysis.

Passive immunization and hypothalamic peptide secretion.

Passive immunization is a common approach used to eliminate the biological activity of an endogenous substance by its binding to a specific antibody (Ab). Surprisingly little information has been gathered on the mechanisms involved. Moreover, the possibility that immunoneutralization could affect also the secretion of the antigen itself has been mostly ignored. To study hypothalamic neuropeptide secretion under the condition of passive immunization, labeled and unlabeled monoclonal antibody (MoAb) against arginine vasopressin (AVP) was injected intravenously. After 2 h a similar amount of 125I-MoAb was found in hypophyseal portal and peripheral (femoral artery) plasma, showing a distribution volume of 73.2 ml/kg. Assessment of the MoAb dilution in the same plasma samples from the binding studies revealed substantially higher dilutions (800-5,700 ml/kg). Such a MoAb dilution (saturation) would be attained by the binding of 130-290 pmol AVP/ml plasma. The calculated amount of plasma AVP decreased by one half within the interval from 2 to 24 h after Ab injection, similarly as did the 125I-MoAb content. Intravenous injection of polyclonal corticotropin-releasing hormone (CRH) Ab resulted in a decrease of plasma adrenocorticotropin and corticosterone levels. After 24 h the dilution of the Ab in portal plasma exceeded two times that in peripheral plasma. CRH concentrations of 0.6-2.5 pmol/ml were found by specific radioimmunoassay after its dissociation from the Ab in plasma. The CRH concentration was higher in portal than in peripheral plasma and was related to the amount of the Ab injected. CRH mRNA levels in the paraventricular nucleus were significantly increased in CRH Ab as compared with normal rabbit serum injected rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasopressin- and oxytocin-immunoreactive hypothalamic neurones of inbred polydipsic mice.

In the late 1950s the inbred polydipsic mice, STR/N, was discovered. The early studies indicated that the extreme polydipsia was not due to a lack of vasopressin but probably due to innate thirst of unknown origin. Because the recent investigation has revealed the presence of some functional abnormality in the brain of the STR/N mouse, we now investigated, using immunohistochemical techniques, distribution of vasopressin (AVP)- and oxytocin (OXT)-containing neurones in the hypothalamus of polydipsic strain of mouse and compared with that of the control. The pattern of distribution of AVP- and OXT-immunoreactive neurones in the paraventricular (PV), supraoptic (SO), and suprachiasmatic nuclei (SCN) of the STR/N polydipsic mouse was similar to that of the control, but the number of AVP-immunoreactive neurones was more numerous in the PVN and SON and less in the SCN in the polydipsic mouse than in the control. In addition, a discrete group of AVP- and OXT-containing neurones that was not clearly seen in the control was discovered in the STR/N. These results implicate that abnormal distribution in the brain AVP and OXT contribute to the mechanism responsible for the polydipsia shown by the strain STR/N.

[Involvement of vasopressinergic neurons of paraventricular nucleus in the electroacupuncture-induced inhibition of experimental visceral pain in rats].

It has been demonstrated in animal model of somatic pain that hypothalamic paraventricular nucleus (PVN) participates in acupuncture analgesia, probably by mediation of vasopressin release. The role of PVN in acupuncture analgesia for experimental visceral pain in rats was further investigated in the present study. Experimental results demonstrated that electroacupuncture could inhibit the writhing response, produced by intraperitoneal injection of antimonium potassium tartrate and this inhibitory effect could be enhanced by electrical stimulation of PVN, but decreased by electrolytical lesion of PVN, intracerebroventricular injection of vasopressin antiserum (14 microliters) or the vasopressin antagonist, d(CH2)5Tyr(Me)-AVP (500 ng/5 microliters). Intraperitoneal administration of the latter drug (10 micrograms/kg), however, was ineffective. The above experimental results suggest that vasopressinergic neurons in PVN also participate in the inhibition of visceral pain by electroacupuncture.

Immunocytochemical and in situ hybridization detection of hypothalamic neuropeptides from postmortem unfixed rat brains.

The effects of postmortem delay on neuropeptide-containing perikarya was studied in the paraventricular nucleus (PVN) of the rat hypothalamus. Serial sections from brains kept in the skull after death for 6 h and immunocytochemically processed for oxytocin (OT), vasopressin (AVP) and corticotropin releasing factor (CRF) or hybridized in situ for CRF resulted in the well preserved phenotypic expression and stability of mRNA of the aforementioned neuropeptides. Furthermore in most cases, AVP and CRF expression was discernibly enhanced relative to prefixed immunopositive tissue. Results of this study suggest that postmortem variables do not significantly alter the neurochemical coding of magnocellular or parvocellular neurosecretory systems, and support the view that rat and human brain topography can be investigated from tissue left in situ after death for a relatively long period of time.

A monoclonal antibody to vasopressin: preparation, characterization, and application in immunocytochemistry.

The hypothalamo-neurohypophysial system, containing the hormones oxytocin (OT) and vasopressin (VP) and their associated carrier proteins, the neurophysins (NPS), has been the subject of extensive investigation for more than 40 years. This system has been reinvestigated during the last decade by application of immunocytochemical methods employing the rabbit antisera to the hormones and NPS. In this study we describe the preparation and characterization of a monoclonal antibody to VP and its application in immunohistochemistry. The antibody did not cross-react with OT or arginine vasotocin (AVT). Its antigenic determinants as characterized by absorption with various VP analogs included two aromatic amino acids: Phe in position 3, and to a lesser extent Tyr in 2. Tissue fixation with formaldehyde resulted in inadequate immunostaining as compared to glutaraldehyde, most likely due to interference with the aromatic amino acid determinants by the former fixative.

Vasopressin-dependent and -independent control of the release of adrenocorticotropin.

We tested the possibility that vasopressin mediates the responses of adrenocorticotropin (ACTH) to electrical stimulation of various areas of the hypothalamus. Thirty-three cats were anesthetized with chloralose-urethane, immobilized with gallamine, and respired artificially. Plasma ACTH was measured by RIA. Intraventricular administration of antiserum to vasopressin blocked the release of ACTH induced by electrical stimulation of the paraventricular nucleus (PVN), suggesting a role for the vasopressinergic projection from PVN to the external zone of the median eminence. In contrast, the release of ACTH induced by stimulation of areas ventral to PVN was unaffected by the antiserum. Thus, there is at least one corticotropin releasing factor released from nuclei other than PVN that is distinct from vasopressin.

The influence of vasopressin on hypothalamic corticotrophin releasing activity in rats with inherited diabetes insipidus.

1. The corticotrophin releasing activity of hypothalamic extracts from rats congenitally lacking vasopressin (Brattleboro strain) has been studied in the presence and absence of arginine vasopressin and its antiserum. 2. Hypothalamic extracts from Brattleboro rats stimulated the production of corticotrophin by pituitary segments in vitro but both their potency and the slopes of their dose-response lines were significantly less than those of controls. Arginine vasopressin also stimulated pituitary-adrenocorticotrophic activity in vitro but only in concentrations considerably greater than those present in hypothalamic extracts from normal rats. 3. In low, physiological concentrations arginine vasopressin did not affect the corticotrophin releasing activity of hypothalamic extracts from controls but potentiated markedly the activity of extracts from Brattleboro rats and rendered the slopes of their dose-response lines parallel with those of the controls. 4. The antiserum to arginine vasopressin did not affect the corticotrophin releasing activity of Brattleboro extracts but reduced the activity of control extracts and rendered the slopes of their dose-response lines parallel with those of Brattleboro extracts. 5. The results suggest that vasopressin acts synergistically with the corticotrophin releasing factor and is essential for the full expression of pituitary-adrenocorticotrophic activity.