Oxytocin-associated Neurophysin Research Articles

Chronic exposure to Δ 9-tetrahydrocannabinol downregulates oxytocin and oxytocin-associated neurophysin in specific brain areas

Cannabinoids are widely abused drugs. Our goal was to identify genes modulated by Δ 9-tetrahydrocannabinol (Δ 9-THC) treatment. We found that chronic administration of Δ 9-THC (1.5 mg/kg/day, i.p.; 7 days) to rats, downregulates the expression of oxytocin-neurophysin (OT-NP) mRNA and of OT and oxytocin-associated NP (NP OT) immunoreactivity in nucleus accumbens (NAc) and ventral tegmental area (VTA), brain areas involved in reward and addiction. Real-time PCR revealed a 60% and 53% reduction of OT-NP mRNA in NAc and VTA, respectively, under chronic treatment, while no changes were observed in NAc after 24 h. Immunohistochemistry showed a large decrease in number of OT and NP OT-stained fibers in NAc (by 59% and 52%, respectively) and VTA (by 50% and 56%, respectively). No changes in cell staining were observed in the paraventricular nucleus and supraoptic nucleus. As OT is known to inhibit development of drug tolerance and attenuate withdrawal symptoms, we suggest that OT downregulation could play a role during the establishment of the chronic effects of Δ 9-THC.

Oxytocin, oxytocin-associated neurophysin and the oxytocin receptor in the human prostate.

Oxytocin has been implicated in the regulation of prostate growth. However, the cellular localisation of oxytocin in the normal and diseased human prostate is not known. Oxytocin, oxytocin-associated neurophysin and oxytocin receptor were detected by immunohistochemistry in tissues from patients undergoing routine prostatectomy and in normal human prostate epithelial and stromal cell lines. Western blot analysis detected a single band at 14 kDa with neurophysin antiserum and a 66-kDa band with oxytocin receptor antiserum in epithelial and stromal cell lines. Similar sized bands were also detected in extracts of hyperplastic and adenocarcinomic prostate tissues. Oxytocin, oxytocin-associated neurophysin and oxytocin receptor were present in stromal and epithelial cell lines and in tissue from patients with benign prostatic hyperplasia. The peptides were localised predominantly to the epithelial cells, although discrete areas of stromal staining were also observed. There was a significant difference in the intensity of oxytocin-staining between tissue displaying benign prostatic hyperplasia and invasive carcinoma, with less immunoreactivity being present in the malignant epithelial cells. Thus, oxytocin and its neurophysin and receptor are present in epithelial and stromal cells of the human prostate. Oxytocin expression is reduced with tumour progression and may provide a marker for invasive disease.

Vasopressin Differentially Modulates Non-NMDA Receptors in Vasopressin and Oxytocin Neurons in the Supraoptic Nucleus

Magnocellular neurons of the supraoptic nucleus release the neuropeptides oxytocin and vasopressin from their dendrites to regulate their synaptic inputs. This study aims to determine the cellular mechanism by which vasopressin modulates excitatory synaptic transmission. Presumably by electroporation through perforated patch, we were able to successfully introduce biocytin into cells in which we performed an electrophysiological study. This method enabled us to determine that roughly half of the recorded neurons were immunoreactive to oxytocin-associated neurophysin and showed two characteristic features: an inward rectification and a sustained outward rectification. The remaining half showed a linear voltage-current relationship and was immunoreactive to vasopressin-associated neurophysin. Using these electrophysiological characteristics and post hoc immunohistochemistry to identify vasopressin or oxytocin neurons, we found that vasopressin decreased evoked EPSCs in vasopressin neurons while increasing EPSCs in oxytocin neurons. In both types of neurons, EPSC decay constants were not affected, indicating that desensitization of non-NMDA receptors did not underlie the EPSC amplitude change. In vasopressin neurons, both vasopressin and a V1a receptor agonist, F-180, decreased AMPA-induced currents, an effect blocked by a V1a receptor antagonist SR49059. In oxytocin neurons, AMPA-induced currents were facilitated by vasopressin, whereas F-180 had no effect. An oxytocin receptor antagonist blocked the facilitatory effect of vasopressin. Thus, we conclude that vasopressin inhibits EPSCs in vasopressin neurons via postsynaptic V1a receptors, whereas it facilitates EPSCs in oxytocin neurons through oxytocin receptors.

Oxytocin and vasopressin expression in the ovine testis and epididymis: changes with the onset of spermatogenesis.

Contractions of seminiferous tubules and epididymal duct walls promote spermiation and sperm transfer, and they are thought to be stimulated by the related peptides oxytocin and vasopressin. This study tested the hypothesis that if oxytocin and/or vasopressin play a physiological role in sperm shedding and transport, then local or circulating concentrations of these peptides would increase during puberty. Testes, epididymides, and trunk blood of sheep at stages during the first spermatogenic wave were collected, and radioimmunoassay measured significant increases in testicular and epididymal oxytocin during spermatogenesis. No changes were measured in circulating oxytocin or in local or circulating vasopressin. Localization and synthesis was investigated by immunohistochemistry and Western blot analysis employing antibodies recognizing epitopes of either oxytocin, oxytocin-associated neurophysin, vasopressin, or vasopressin-associated neurophysin. Marked expression of both oxytocin and its associated neurophysin in testicular Leydig and epididymal principal cells was seen, and weak neurophysin immunoreactivity was also identified in Sertoli cells. The intercellular distribution of oxytocin varied between regions of the epididymis, suggesting several roles for oxytocin. Vasopressin synthesis was not apparent in either tissue. These results confirm the presence and development of paracrine oxytocinergic systems in the ram testis and epididymis of ram during puberty while questioning the physiological importance of vasopressin.

Effects of electroconvulsive therapy on plasma vasopressin and oxytocin

Background: Animal studies suggest that vasopressin has cognitive-enhancing properties and oxytocin may have amnestic effects. A clinical report suggests that the acute increase in oxytocin-associated neurophysin predicts clinical response to electroconvulsive therapy (ECT) in depressed patients. Methods: Medication-free patients with major depression were randomized to receive right unilateral or bilateral ECT administered with electrical stimulus intensity at either just above seizure threshold or at 150% above seizure threshold. The associations between plasma vasopressin, oxytocin, ECT treatment parameters, clinical outcome, and cognitive effects were assessed. Results: The sample comprised 55 patients. At the second ECT, patients receiving ECT at 150% above initial seizure threshold had significantly greater increases in plasma vasopressin than patients receiving low-dose ECT ( ps < .01–.04), with no effects of electrode placement. At the second and ninth ECT treatments, the vasopressin or oxytocin surges were not associated with clinical improvement, seizure duration, time to orientation, or memory test performance. There were inverse trend-level associations between the acute surge in oxytocin levels at the ninth ECT and clinical response, contradicting a report in the literature. Conclusions: Overall, these findings do not support the hypothesis that diencephalic seizure propagation is central to the mechanism of action of ECT.

Increased expression of the N-methyl- d-aspartate receptor subunit, NR1, in immunohistochemically identified magnocellular hypothalamic neurons during dehydration

N-Methyl- d-aspartate receptors are thought to be involved in synaptic signaling within the hypothalamo-neurohypophysial system, but the extent and nature of their involvement has not been determined. In this study, in the rat, we evaluated the effect of hyperosmotic stimulation on the N-methyl- d-aspartate receptor subunit, NR1, which confers function to N-methyl- d-aspartate receptor heteromers. Co-localization of immunoreactivity for NR1 and vasopressin- or oxytocin-associated neurophysin in magnocellular neurons of the supraoptic and paraventricular hypothalamic nuclei was accomplished using double-label immunohistochemistry. Our results show that vasopressin- and oxytocin–neurophysin-positive populations contained detectable levels of NR1 labeling. Using NR1 labeling as a measure of N-methyl- d-aspartate receptor density, we examined the effect of dehydration in these nuclei. Using computer-assisted densitometry, we found significantly greater NR1 labeling densities in the magnocellular regions of both the supraoptic and paraventricular nuclei of saline-treated rats than of control rats. This increase was not due to methodological factors, since no changes in NR1 labeling density were found in a nearby nucleus, the nucleus reuniens. Western blot analysis showed similar selective increases in NR1 labeling in homogenates from the supraoptic nucleus, paraventricular nucleus and in some cases from the anterior hypothalamic area. In both immunohistochemical and western blotting experiments we did not observe a dehydration-induced increase in NR1 in other brain areas examined. Our results showing an up-regulation of NR1-containing N-methyl- d-aspartate receptors during dehydration suggest that these receptors are involved in the regulation of body water and may represent an adaptive physiological response following activation of the hypothalamo-neurohypophysial axis. In addition, these results suggest that the functional expression of N-methyl- d-aspartate receptors is dynamic and may be modified according to the physiological state of the animal.

Neuroendocrine and clinical effects of electroconvulsive therapy and their relationship to treatment outcome

Two groups of variables, endocrine and clinical, have been reported to have predictive value in determining response to electroconvulsive therapy (ECT) in depressed patients. Baseline levels of oxytocin associated neurophysin (OAN) and peak OAN response to ECT may predict clinical outcome, while the presence of delusional symptoms may indicate favourable initial response to ECT. The purpose of this study was to examine the relationship between these variables on initial and longer term response over a course of ECT, using a direct measure of plasma oxytocin concentrations. A substantial and immediate increase in oxytocin was seen after the first ECT, with significantly attenuated responses after the third and fifth ECTs. Increased plasma vasopressin concentrations were seen after all ECT treatments, each response being of similar magnitude. No associations were found between either endocrine baseline levels or peak responses, and clinical outcome. Only clinical variables predicted outcome, as patients with psychotic symptoms had more rapid initial response to ECT, and patients who had relapsed 2 months after the end of ECT had significantly higher depression ratings at day 14 of treatment than treatment responders.

Development of Oxytocinergic Neurons in Monolayer Cultures Derived from Embryonic, Fetal and Postnatal Rat Hypothalami

Monolayer cultures from hypothalami of embryonic, fetal and postnatal rats were established to study the development of oxytocin-secreting neurons in vitro. Particular culture conditions, known to enhance the survival and growth of different types of neural cells in vitro, were used to investigate the conditions necessary for the appearance and survival of these peptide-producing cells in culture. They included increasing the concentration of potassium in the culture milieu and/or the addition of triiodothyronine (T(3) ). The use of immunocytochemical procedures with a monoclonal antibody that recognizes oxytocin-associated neurophysin (NP-OT) and polyclonal antibodies specific for oxytocin permitted us to identify the neurons. In cultures derived from embryonic (E16-E17) hypothalami, no NP-OT- or oxytocin-positive neurons were detected and their appearance could not be provoked by increasing extracellular potassium concentration or by administration of T(3) . On the other hand, in cultures obtained from fetal (E18-E19) rat hypothalami, a few neurons showed immunoreactivity for NP-OT (but not for oxytocin); the immunoreactivity was localized essentially in somata and proximal portions of neurites. When 10(8) M T(3) was included in the culture medium, there were cells showing immunoreactivity not only for NP-OT, but also for oxytocin, visible in somata and in dendritic- and axonal-like processes. In comparison, T(3) did not influence the total number of neurons developing in these cultures. Lastly, in cultures derived from young postnatal (PO-P2) rat hypothalami, NP-OT- and oxytocin-immunopositive neurons were found regularly; their appearance did not require any special pretreatment of the cultures. In all cultures, high extracellular potassium concentration (25 mM) resulted in a general improvement in the survival of neurons but did not induce the appearance of more oxytocin-immunoreactive cells. Our observations support in vivo results showing that although presumptive oxytocin-producing cells appear early in the development of the hypothalamus, their maturation, and in particular, their ability to produce oxytocin, occurs late at the time of birth. A factor that selectively enhances their differentiation, is the thyroid hormone, T(3) .

Absence of negative feedback by oxytocin on release from magnocellular neurones in conscious rats.

Peripheral administration of vasopressin (VP) was previously shown to exert a negative feedback influence on its own release and on the release of oxytocin (OT). In this study we examined the possible influence that OT has on the function of hypothalamic magnocellular neurones. Oxytocin was administered intraperitoneally and its effects on release from VP neurones and from OT neurones were determined as indexed by plasma concentrations of vasopressin-associated neurophysin ([VP-RNP]) and oxytocin-associated neurophysin ([OT-RNP]) under basal conditions and conditions of high plasma osmolality (Posm) induced by acute salt loading. Studies were performed on conscious, chronically instrumented Long-Evans rats. Oxytocin (1 nmol or 10 nmol) dissolved in 1 mL of 0.9% saline was administered intraperitoneally to animals 1 h before they received an intravenous infusion of hypertonic saline over 60 min at a rate designed to raise Posm by approximately 0.75 mosmol.min-1. Intraperitoneal injection of vehicle or 1 nmol of OT did not significantly alter [VP-RNP], [OT-RNP], or basal Posm. Administration of 10 nmol OT also had no effect on [VP-RNP] or [OT-RNP], but this dose of peptide significantly lowered basal Posm (299 +/- 2 to 290 +/- 2 mosmol/kg H2O, p less than 0.001). Both doses of OT did not significantly alter the responsiveness of VP neurones to hyperosmotic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement in depressive illness is not associated with altered release of neurophysins over a course of ECT

The hypothesis that the release of vasopressin-associated neurophysin (hNpI) or oxytocin-associated neurophysin (hNpII) is modified by a course of electroconvulsive therapy (ECT) was tested by the measurement of serum neurophysins before and after the first and last ECTs given to 17 unipolar depressed patients. Neither basal nor ECT-induced neurophysin release changed between the first and last ECTs. Data from the present study were combined with data from a previous published study to provide a sample of 29 unipolar depressed patients. In this extended sample, the release of hNpII after the first ECT was significantly correlated with improvement in symptoms of depression over a course of ECT as measured by the Hamilton Rating Scale for Depression and the Montgomery- Åsberg Depression Rating Scale.

Influence of Pentobarbital and Urethane on Release from Magnocellular Neurons

We examined the responses of vasopressin-neurons (VP-neurons) and oxytocin-neurons (OT-neurons) to acute salt-loading in a group of conscious rats (CON, n = 8) and rats under sodium pentobarbital (NEM, 50 mg/kg, i.p., n = 8) or urethane (URE, 1.6 g/kg, i.p. n = 8) anesthesia. Fifteen minutes following the induction of anesthesia, sodium pentobarbital produced an increase in basal plasma osmolality (Posm, 290 +/- 2 to 296 +/- 3 mosm/kg H2O, p less than 0.007) while urethane did not change basal Posm (287 +/- 2 to 289 +/- 2 mosm/kg H2O). Neither anesthetic agent resulted in any significant changes in basal plasma levels of vasopressin-associated neurophysin (VP-RNP) and oxytocin-associated neurophysin (OT-RNP). In response to intravenous infusion of 18% saline, all three groups of rats had similar rises in Posm. The slopes of the relationship between the rise in plasma VP-RNP and the rise in Posm were markedly reduced in both groups of anesthetized animals compared to that observed for conscious animals (CON = 2.54 +/- 0.5; NEM = 1.22 +/- 0.18; URE = 1.17 +/- 0.24 fmol.ml-1.mosm-1.kg H2O-1 p less than 0.0126). The slopes of the relationship between the rise in plasma OT-RNP and the rise in Posm were not significantly (p less than 0.4478) different between the CON group and the NEM group, while the slope for the URE group was significantly (p less than 0.05) smaller than that for the CON group (CON = 10.9 +/- 1.5; NEM = 9.3 +/- 1.5; URE = 6.3 +/- 0.7 fmol.ml-1.mosm-1.kg H2O-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of opioid peptides on release from vasopressin and oxytocin neurones of the hypothalamoneurohypophyseal system: effects of naloxone in the conscious rat

We examined the effects of acute and chronic treatments with naloxone on release of vasopressin and oxytocin from the hypothalamoneurohypophyseal system (HNS) in conscious, chronically instrumented Long-Evans rats. Plasma concentrations of vasopressin-associated neurophysin and oxytocin-associated neurophysin were evaluated before and during an intravenous infusion of 18% saline at 100 microL.kg-1 body weight.min-1 for 60 min. Acute treatment with naloxone (2.75 mumol/kg, intravenous) did not measurably alter basal plasma osmolality or vasopressin-associated neurophysin concentration, but it caused a three-fold rise in basal plasma oxytocin-associated neurophysin concentration (16 +/- 2 to 46 +/- 3 fmol/mL, p less than 0.005). Chronic treatment with naloxone (13.75 mumol/day, subcutaneous pellets) increased plasma osmolality (292 +/- 1 to 300 +/- 2 mosmol/kg H2O, p less than 0.01) by day 5, but it had no measurable effects on basal vasopressin- or oxytocin-associated neurophysin concentration. There were also no significant differences in plasma sodium concentration (144.8 +/- 1.1 vs. 142.2 +/- 1.4 mequiv./L) under both conditions. Acute and chronic treatments with naloxone accompanied by salt loading produced a five- and four-fold decrease in the rates that plasma concentration of vasopressin-associated neurophysin changed with plasma osmolality, compared with untreated salt-loaded control rats. For oxytocin secretion from the HNS, both treatments accompanied by salt loading substantially decreased the threshold for changes in relation to plasma osmolality; the rise in plasma concentration of oxytocin-associated neurophysin was similar at all levels of hyperosmotic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment outcome, seizure duration, and the neurophysin response to ECT

Serum concentrations of immunoreactive neurophysin (IRN) and vasopressin-associated neurophysin (hNpI) were measured before and after the first treatment in a course of electroencephalographically monitored electroconvulsive therapy (ECT) given to 19 depressed patients. The difference (DIFF) between the serum concentrations of IRN and hNpI is equivalent to the concentration of oxytocin-associated neurophysin. Before ECT the six patients who had a good outcome at 2 months after the course of ECT had a mean serum IRN concentration one-half ( p < 0.05) and a mean serum DIFF concentration one-third ( p < 0.05) that of the 13 patients who had a poor outcome. The increase in serum DIFF concentration (but not IRN or hNpI) after the first ECT correlated with the improvement on the Hamilton Rating Scale for Depression (r = −0.73, p < 0.005) and the Montgomery and Asberg Depression Rating Scale (r = − 0.49, p < 0.05). The peak percentage increase in serum DIFF concentrations after ECT was 4 times greater (p < 0.001) in the good outcome group than in the poor outcome group. None of the neurophysin responses to ECT correlated with electroencephalogram-measured seizure duration.

Distributions of pro-vasopressin expressing and pro-vasopressin deficient CRH neurons in the paraventricular hypothalamic nucleus of colchicine-treated normal and adrenalectomized rats.

The corticotropin-releasing hormone (CRH) neurosecretory system in normal rats consists of two major subpopulations of parvicellular neurons in the hypothalamic paraventricular nucleus distinguished by the presence or absence of coexistent vasopressin precursor (pro-AVP)-derived peptides. These neurons project to the external zone of the median eminence, where the two subtypes of axons (CRH +/AVP + and CRH+/AVP-) were previously found to be approximately equal in number. The present study was undertaken 1) to determine whether the relative numbers of pro-AVP expressing and pro-AVP deficient perikarya in the paraventricular nucleus corresponded to what we previously found for the axons in the median eminence, 2) to map the two cell types throughout the entire paraventricular nucleus to determine whether significant differences existed in their distributions, and 3) to ascertain whether or not the pro-AVP deficient subpopulation expressed pro-AVP after adrenalectomy. Postembedding electron microscopic immunocytochemistry on serial ultrathin sections was used to identify the peptide phenotypes of perikarya in the paraventricular nucleus in normal rats and 7 days after adrenalectomy with and without colchicine treatment. The peptide phenotypes of neuronal perikarya in the paraventricular nucleus were identified by using antibodies to CRH, AVP, neurophysin (NP), the C-terminal glycopeptide of pro-AVP (GP), and oxytocin-associated neurophysin (NPOT). Groups of three serial coronal ultrathin sections were analyzed at 200-micron intervals throughout the entire rostrocaudal extent of the paraventricular nucleus. The sections in each group were stained for CRH, a pro-AVP-derived peptide (AVP, NP, or GP), and NPOT, respectively. Parvicellular CRH neurons were defined as CRH-positive cells, approximately 10 micron in diameter, that did not contain detectable NPOT. Pro-AVP expressing cells were defined as staining positively for AVP, GP, or NP and negatively for NPOT. Approximately equal numbers of pro-AVP expressing ("NPAVP+") and pro-AVP deficient ("NPAVP-") parvicellular CRH neurons were found within the paraventricular nucleus of colchicine-treated normal rats, and the two subtypes were distributed differently within the paraventricular nucleus. Although the pro-AVP expressing CRH cells stained intensely for NP and GP, staining for AVP was quite variable and difficult to quantify in colchicine-treated normal animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Major pro-vasopressin-expressing and pro-vasopressin-deficient subpopulations of corticotropin-releasing hormone neurons in normal rats. Differential distributions within the paraventricular nucleus.

Two approximately equal subpopulations of corticotropin-releasing hormone (CRH)-containing parvocellular axons can be identified in the external zone of the median eminence in normal (unadrenalectomized) rats: one that contains pro-vasopressin (AVP)-derived peptides (i.e. AVP, AVP-associated neurophysin and the carboxy terminal glycopeptide) copackaged with CRH in secretory vesicles, and another that contains no detectable pro-AVP-derived peptides. In this study, antibodies to pro-AVP-derived peptides were used to demonstrate for the first time that similar subpopulations of CRH-containing parvocellular perikarya exist in the paraventricular nucleus of the hypothalamus in normal rats treated with colchicine. Electron-microscopic immunocytochemistry was performed on serial ultrathin sections to identify neurosecretory cell perikarya containing CRH that also expressed pro-AVP peptides or pro-oxytocin-derived neurophysin. Of the CRH-positive neurons that were detected, more than half stained positively for two pro-AVP peptides: AVP-associated neurophysin and the carboxy-terminal glycopeptide. Many of these cells also stained for AVP, but staining was variable, making quantitation of AVP-positive cells difficult. The remaining CRH-positive neurons contained no detectable pro-AVP peptides, and less than 0.5% of these CRH perikarya contained oxytocin-associated neurophysin. In the neurons that stained positively for both CRH and the pro-AVP peptides, CRH and the pro-AVP peptides were localized in the same secretory vesicles. The pro-AVP expressing and pro-AVP-deficient CRH neurons were distributed differently within the paraventricular nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurophysin in the large luteal cell of the nonpregnant water buffalo (Bubalus bubalis): immunohistochemical localization.

Light microscopy immunohistochemistry was used to localize neurophysin in the corpus luteum of the mid-luteal phase of the estrous cycle of the water buffalo (Bubalus bubalis). Corpora lutea weighing 0.39-0.65 g from a recent ovulation showed no staining. Corpora lutea identified with the late luteal phase showed only weak evidence of staining. The neurophysin staining was confined to a specific region of large oval-shaped cells (20-30 microns diameter), which had a very eosinophilic cytoplasm. The intense localization of staining to a distinct area of the cytoplasm was previously only observed in the corpus luteum of the cow. Corpora lutea obtained from all quadrants of pregnancy did not stain. Controls in which the neurophysin antiserum was substituted with serum from an unimmunized rabbit (normal rabbit serum) or neurophysin antiserum preabsorbed with bovine oxytocin-associated neurophysin I also did not stain. These data indicate the neurophysin is present in the mature corpus luteum of the nonpregnant water buffalo as it is in other nonpregnant ruminants, the ewe and cow.

Immunocytochemical studies of vasotocin, mesotocin, and neurophysins in the Xenopus hypothalamo-neurohypophysial system.

Mesotocinergic and vasotocinergic neurons, which constitute the principal neurons in the hypothalamo-neurohypophysial system in Xenopus, were studied by immunocytochemical techniques. Antibodies that could unequivocally distinguish mesotocin, vasotocin, and their respective neurophysins were used in these studies. A monoclonal antibody directed at rat oxytocin-associated neurophysin (PS-36) detected an antigen that was colocalized with vasotocin, whereas a monoclonal antibody to rat vasopressin-associated neurophysin (PS-45) crossreacted with an antigen in mesotocinergic cells. As vasotocin is regarded as an evolutionary precursor of vasopressin, and as mesotocin is usually associated with oxytocin, we were surprised to see this apparent eptitope switch in the associated neurophysins. One interpretation of this epitope switch is that the final exons encoding for the carboxy-terminals of the mammalian neurophysins, which contain the PS-45 and PS-36 antibody epitopes, are in reversed positions in Xenopus. Approximately 4,000 mesotocinergic and vasotocinergic neurons and their fibers were topographically mapped in the Xenopus hypothalamus. The two types of neurons were intermingled and scattered throughout a large contiguous region including but not limited to the preoptic recess. Small, medium size, and large cells contained these antigens. Immunoreactive fibers were seen in the preoptic area, the neurohypophysial tract, the median eminence, and the neural lobe of the pituitary. The neurophysin-specific monoclonal antibodies have several advantages as phenotypic markers in development; i.e., high titer, low background, and affinity for the prohormone forms as well as for the fully processed neurophysin polypeptides. Their antigens are related gene products whose expression is central to the identity of the two cell types and whose expression is differentially controlled in development. This characterization of their adult distribution provides a basis for future studies of the development of peptidergic phenotype in the central nervous system of Xenopus.

Effect of systemic intravenous infusion of PGF-2 alpha and 13,14-dihydro-15-keto-PGF-2 alpha on the release of oxytocin-associated neurophysin from the ovary in the ewe.

Systemic intravenous infusion of physiological concentrations of PGF-2 alpha and its major metabolite, 13, 14-dihydro-15-keto-PGF-2 alpha (PGFM) into non-pregnant ewes possessing a corpus luteum induced the release of oxytocin-neurophysin. These results suggest that, during luteolysis, endogenous release of uterine PGF-2 alpha would be able to stimulate the release of ovarian oxytocin and oxytocin-neurophysin from the ovary.

Effect of systemic or intrauterine injections of indomethacin on plasma oxytocin-neurophysin concentrations in ewes over the time of normal corpus luteum regression.

This study was undertaken to investigate the effect of systemic or intrauterine injections of indomethacin, a known prostaglandin (PG) synthetase inhibitor, on peripheral plasma oxytocin-associated neurophysin (OT-N) concentrations in ewes over the time of expected luteolysis. In the first experiment, 9 ewes were given i.m. injections of indomethacin (4 mg/kg live weight, n = 4) or vehicle (n = 5) 3 times/day over Days 13-15 of the estrous cycle. Blood samples were collected at hourly intervals from 0700 h on Day 13 to 1800 h on Day 15 post-estrus. In the second experiment, indomethacin (20 mg, n = 5) or the injection vehicle (n = 4) was given twice daily into the uterine horn over Days 12-14 post-estrus. Blood samples were collected at hourly intervals from Day 12 to 14. In the third experiment, 4 additional ewes were bled at 5-min intervals from 1200 to 1600 h on Day 13 of the estrous cycle. Plasma samples were analyzed for OT-N and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) to provide an indirect index for ovarian oxytocin and uterine prostaglandin F2 alpha release, respectively. Results from the first experiment indicated that surges in plasma OT-N concentrations occurred in the vehicle-treated ewes but were suppressed in ewes given systemic injections of indomethacin. Intrauterine indomethacin injections did not cause a significant reduction in the maximum peak height or number of peaks when compared with the control ewes. In the third experiment, there was a marked increase in plasma OT-N concentrations, but no significant rise in plasma PGFM concentrations in one ewe.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intraperitoneal injection of lithium chloride on neurohypophyseal activity: Implications for behavioral studies

Intraperitoneal injections of lithium chloride (LiCl) were found to increase the activity of vasopressin-neurons and oxytocin-neurons as indexed by rises in plasma concentrations of vasopressin-associated neurophysin (VP-RNP) and oxytocin-associated neurophysin (OT-RNP). Plasma VP-RNP increased 12 and 4 times basal levels (≧20 fmol/ml) reaching values of 248±37 fmol/ml (3.0 mEq LiCl/kg body weight) and 89±10 fmol/ml (1.5 mEq LiCl/kg body weight) at 60 minutes. OT-RNP rose to 37- and 10-times basal levels (≧20 fmol/ml) with peak values of 749±100 fmol/ml and 188±48 fmol/ml ten minutes following injection of 3.0 or 1.5 mEq LiCl/kg body weight. Mean arterial pressure increased in response to lithium treatment by 31±6 mm Hg at 60 minutes in rats receiving 3.0 mEq LiCl/kg and by 22.5±5 mm Hg at 10 minutes in rats receiving 1.5 mEq LiCl/kg over pretreatment values (125±3 mm Hg). Heart rate decreased from a pretreatment value of 422±12 beats/min to 367±48 beats/min at 10 minutes and to 341±27 beats/min at 20 minutes for rats treated with the high and low dose of lithium, respectively. These findings suggest that the behavioral effects of LiCl could result from multiple mechanisms and involve its acute release of vasopressin and oxytocin. It is also possible that changes in cardiovascular function may act as cues when LiCl is used as an aversive stimulus.