Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hypothalamic suprachiasmatic nucleus (SCh) is the principal brain structure involved in the generation of circadian rhythms. In the present study, we have employed immunohistochemical techniques to evaluate the development of the fetal SCh following its transplantation to the brain of adult host animals. Donor hypothalami were obtained from normal Long-Evans fetuses and transplanted to the lateral, third, or fourth ventricle of Brattleboro rats. Neuronal aggregations exhibiting the organotypic features of the SCh were present in over 90% of the grafts recovered at each transplantation site. Like the normal endogenous SCh, SCh-like cell groups identified within the transplants contained a prominent population of parvicellular (9-13 micron), neurophysin-containing neurons that were immunopositive for vasopressin (VP) but not oxytocin. These SCh-like cell groups also invariably contained similar small neurons that were immunoreactive for vasoactive intestinal polypeptide (VIP). Typically, VP and VIP immunoreactive perikarya were concentrated in contiguous, complementary parts of the grafted SCh, but fibers immunoreactive for either peptide were distributed throughout the extent of the nucleus. Because the brain of the Brattleboro rat is deficient in vasopressin, it was possible to evaluate the projection of the vasopressinergic component of the transplanted SCh to the host brain. Although SCh were identified in grafts recovered from each intraventricular transplantation site, an appreciable input to the host brain could be identified only when the fetal tissue was grafted to the third ventricle. Here, grafted SCh established efferent connections with periventricular diencephalic structures which ordinarily receive a projection from the in situ SCh. Specifically, VP immunoreactive fibers originating from transplanted SCh were identified in the medial preoptic area, the periventricular and dorsomedial hypothalamic nuclei, the paraventricular nuclei of the thalamus and hypothalamus, and in the retrochiasmatic area, arcuate nucleus, and suprachiasmatic nucleus of the host brain. These results demonstrate that the fetal SCh not only survives transplantation but also retains its distinguishing cytological features and the capacity to form an appropriately restricted set of efferent connections with the brain of adult host animals.
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PMID:Organization and efferent connections of transplanted suprachiasmatic nuclei. 334 77

Immunoreactive vasopressin and oxytocin were measured in the hypothalamo-hypophysial portal blood of both Long-Evans and homozygous Brattleboro rats. Adrenalectomy caused an increase in vasopressin immunoreactivity in portal blood in the Long-Evans strain, whilst administration of dexamethasone to these adrenalectomized animals resulted in a reduction in portal vasopressin immunoreactivity to levels below those seen in sham-operated animals. This vasopressin immunoreactivity co-eluted with synthetic vasopressin on high-pressure liquid chromatography (HPLC), and diluted in parallel in radio-immunoassay. In Brattleboro rats, however, although vasopressin-like immunoreactivity was detected, the portal concentration did not vary with the adrenal status of the animal, nor did it show the characteristics of standard vasopressin on HPLC or in immunoassay. Oxytocin was present in the portal blood of both Long-Evans and Brattleboro rats at similar very high concentrations, but did not vary in response to adrenalectomy. These results are consistent with a role for vasopressin, but not oxytocin, in the hypothalamic response to adrenalectomy and glucocorticoid feedback. Neither vasopressin immunoreactivity nor oxytocin appear to subserve this role in the homozygous Brattleboro rat.
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PMID:Immunoreactive vasopressin and oxytocin in hypothalamo-hypophysial portal blood of the Brattleboro and Long-Evans rat: effect of adrenalectomy and dexamethasone. 335 57

Heterozygous Brattleboro (HZ) rats exhibit a partial genetic deficiency in hypothalamic vasopressin (VP) production. The effects of this abnormality of HZ rats on the capacities of VP-neurons and oxytocin (OT)-neurons to respond to an acute salt-load were examined. Acute salt-loading was induced by intravenous infusion of 18% saline in conscious, chronically catheterized animals and the activities of VP-neurons and OT-neurons were interpreted from plasma concentrations of VP-associated neurophysin, [VP-RNP] and OT-associated neurophysin, [OT-RNP] at different time periods throughout the infusion. Plasma sodium concentration ([Na+]), plasma osmolality (Posm) and mean arterial pressure (MAP) were also monitored. Salt-loading produced significant rises in [VP-RNP] and [OT-RNP]. These rises were accompanied by increases in plasma [Na+], Posm and MAP. Releases of OT-RNP were approximately four times greater than those of VP-RNP. The responsiveness of VP-neurons to increases in Posm in the HZ rat was approximately one-half of that observed for the Long-Evans (LE) rat. Furthermore, the responsiveness of OT-neurons in these animals was approximately one-half of that for LE rats and one-third of that for homozygous Brattleboro (DI) rats. The changes in MAP during salt-loading do not appear to be different for HZ and LE rats. Hence, while VP may be involved in the rise in blood pressure during infusion of hypertonic saline, there is not a direct correlation between plasma levels of VP-RNP (and presumably VP) and rises in blood pressure.
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PMID:Reduced responsiveness to acute salt-loading of vasopressin-neurons and oxytocin-neurons in the heterozygous Brattleboro rat. 357 2

1. Extracellular recordings in pentobarbitone anaesthetized male Long-Evans rats examined the influence of electrical stimulation in the diagonal band of Broca on the excitability of 113 putative vasopressin-secreting and 22 putative oxytocin-secreting neurosecretory neurones in the hypothalamic supraoptic nucleus. 2. Single pulse or repetitive (5-20 Hz) stimulation in the ventral part of the diagonal band evoked a prominent reduction in the excitability of 83% of vasopressin-secreting neurones with no effect on the remainder. Amongst oxytocin-secreting neurones, 59% were unresponsive, 27% responded with an increase in activity while only 14% revealed an inhibitory pattern similar to vasopressin-secreting neurones. 3. Diagonal band stimulation-evoked inhibitions were reversibly abolished by local pressure applications of bicuculline methiodide (100 microM) to twenty out of twenty vasopressin secreting cells tested, whereas strychnine sulphate (100 microM) was without effect on four out of four cells tested. 4. In five out of five vasopressin-secreting cells tested, bicuculline applications reversibly abolished the reduction in their activity that follows peripheral baro-receptor activation. Failure to alter baroreflex-evoked depressions in firing during similar trials with prazosin hydrochloride (10 microM, six cells tested), timolol maleate (20 microM, six cells tested) or strychnine sulphate (100 microM, three cells tested) indicated the specificity of bicuculline's action. 5. These findings suggest that a GABAergic pathway from the diagonal band of Broca preferentially innervates vasopressin-secreting neurosecretory supraoptic nucleus (s.o.n.) neurones, and support the view that the baroreflex-induced depression in firing of s.o.n. vasopressin-secreting neurones is mediated in large part through this input.
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PMID:A gamma-aminobutyric-acid-mediated baroreceptor input to supraoptic vasopressin neurones in the rat. 362 45

The possibility of a functional relationship between noradrenaline and neurohypophyseal peptides in the control of cardiovascular function in the nucleus tractus solitarius of rats has been investigated. The hypotensive response to microinjections of noradrenaline (20 nmol) was abolished by simultaneous (but not prior) microinjections of [Arg8]vasopressin (AVP) and oxytocin at doses (0.9 pmol) which alone had no effects on cardiovascular parameters. AVP plus noradrenaline actually resulted in a transient pressor effect. Simultaneous administration of [deamino-D-Arg8]vasopressin, a selective agonist of AVP V2 receptors, did not modify the effect of noradrenaline, whereas the specific V1 antagonist D-(CH2)5-Tyr(Me)-AVP partially decreased its intensity. When subthreshold doses of both AVP (0.9 pmol) and noradrenaline (10 pmol) were administered simultaneously, a pressor response was observed. In vasopressin-deficient Brattleboro rats, microinjections of 0.9 pmol AVP had no effects, but a marked pressor response was observed after the administration of a higher dose (9 pmol). In parent strain Long-Evans rats, noradrenaline (20 nmol) also produced a hypotensive response, but in Brattleboro rats microinjections of this amine elicited a marked pressor effect. In these rats, simultaneous administration of a subthreshold dose of AVP (0.9 pmol) reversed this response in such a way that a fall in blood pressure, similar to that observed in Long-Evans rats after injection of noradrenaline alone, was registered. These results provide evidence for a functional interaction between noradrenaline and neurohypophyseal peptides in the control of cardiovascular function in the brainstem.
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PMID:Evidence for a functional relationship between noradrenaline and neurohypophyseal peptides in the brainstem of rats. 367 90

These experiments were designed to characterize the nature and extent of diabetes insipidus present in a new model of genetic vasopressin (VP) deficiency, the Roman high avoidance rat homozygous for diabetes insipidus (RHA: di/di strain). The new strain was developed from an initial cross between Long-Evans derived Brattleboro (LE:di/di) rats and normal Roman high avoidance (RHA: +/+) rats, and has been bred to be congenic with the parent RHA: +/+ strain. RHA: di/di rats exhibited polydipsia, excreted dilute urine, and exhibited elevated plasma osmolality. RHA: di/di rats shows a similar urinary response to dehydration as LE: di/di rats. VP was undetectable by radioimmunoassay in the serum, brain, and neurohypophysis of RHA: di/di rats. VP-neurophysin containing cells were not observed in the brains of RHA: di/di rats upon immunocytochemical analysis. Thus, the new RHA: di/di strain exhibits essentially the same profile of diabetes insipidus as the LE: di/di rat. The congenic relationship between RHA: di/di and RHA: +/+ rats makes the RHA: di/di rat a useful model under circumstances where genetic variables unrelated to VP deficiency may confound the interpretation of data.
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PMID:Characterization of a new rodent model of diabetes insipidus: the Roman high avoidance rat homozygous for diabetes insipidus. 373 82

We examined the renal effects of synthetic oxytocin (OT) in the presence and absence of vasopressin in conscious euvolemic rats. Both sexes of the Long-Evans (LE) and Brattleboro homozygous (DI) strains were used. OT infused intravenously at 0.25 and 2.5 ng X min-1 X 100 g body wt (BW)-1 resulted, respectively, in plasma concentrations of 30 +/- 6 and 265 +/- 88 pg/ml in LE rats and 46 +/- 5 and 327 +/- 29 pg/ml in DI rats. Glomerular filtration rate (GFR) was augmented most consistently by the larger dose of hormone in LE rats (P less than 0.05), whereas the low infusion rate of OT enhanced GFR in DI rats (P less than 0.01). Effective renal plasma flow was not changed significantly. OT (both doses) increased the fractional excretion of sodium two- to threefold in each strain of animal (all at least P less than 0.05 from control), whereas the fractional excretion of potassium was largely unaffected. In LE rats, a diuresis was observed with either infusion rate of hormone, accompanied by a rise in osmolar clearance (COsm). In contrast, there was no change of urine flow with the low dose of OT in DI rats, because COsm increased and the clearance of free water (CH2O) decreased proportionately. The higher infusion rate of OT promoted antidiuresis in DI rats, with negative CH2O and little change in COsm. We conclude that oxytocin enhances GFR and is natriuretic regardless of the presence or absence of endogenous vasopressin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of oxytocin on renal hemodynamics and electrolyte and water excretion. 374 Feb 76

Oxytocin (OT) and vasopressin (VP) have been localized to numerous central nervous system locations outside the classic hypothalamo-neurohypophyseal tract including all levels of the spinal cord. To date, the physiological function of these peptides within the spinal cord is unknown. The purpose of this study was to determine if the variations exhibited by pituitary OT and VP during the stages of the estrous cycle in the rat were also present in the spinal cord. The stage of the estrous cycle was determined by vaginal smears in female Long Evans rats. Following decapitation, the cervical, thoracic, and lumbosacral segments of the spinal cord were isolated and homogenized, and the hormones were extracted from the tissue with the Sep-pak method. OT and VP content were determined by RIA. A cyclic variation in spinal cord OT and VP was present, with maximal levels occurring in diestrus, a time in the estrous cycle when LH and estradiol levels are lowest. Our results suggest that spinal cord OT and VP may be regulated by ovarian hormones. These data represent the first documented changes in spinal cord levels of OT and VP under physiological conditions.
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PMID:Cyclic variations in spinal cord levels of oxytocin and vasopressin during the stages of the rat estrous cycle. 383 65

We studied the responses of the hypothalamo-neurohypophysial system to intravenous infusions of 18% saline, 25% mannitol and a combination of 15% mannitol and 1.35% saline in conscious, chronically catheterized Long-Evans rats. Infusions of 18% saline and 25% mannitol produced similar increases in plasma osmolality (Posm) and plasma vasopressin-associated neurophysin concentration [( VP-RNP]). As expected, plasma sodium concentration [( Na+]) for the 18% saline-treated animals was significantly elevated while that for the 25% mannitol-treated animals was significantly reduced. Mannitol infusion caused a significantly greater loss of body weight. The slopes of the relationship between delta [VP-RNP] and delta Posm were almost identical for the two groups. Infusion of a combination of 15% mannitol and 1.35% saline produced a rise in Posm comparable to that observed for the other two infusion regimens, but caused smaller increases in [VP-RNP], the slope of the relationship between delta [VP-RNP] and delta Posm being about half of those for the infusion with 18% saline or 25% mannitol. This combination also maintained [Na+] close to normal levels and in these animals there was a loss of body weight that was significantly smaller than that for those rats receiving 25% mannitol. The results of this study imply that factors other than osmoreceptors and/or sodium receptors are involved in causing a release of neurohypophysial principles during acute infusion of hypertonic solutions.
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PMID:Effects of acute increases in plasma osmolality on plasma vasopressin-associated neurophysin in conscious rats: implications for osmoregulation. 392 63

Plasma oxytocin-associated neurophysin concentration [( OT-RNP]) was used to evaluate the responsiveness of oxytocinergic neurons to an acute salt load in Long-Evans (LE) rats and Brattleboro homozygous (DI) rats. This responsiveness was compared with that of vasopressinergic neurons in LE rats as indexed by plasma vasopressin-associated neurophysin concentration [( VP-RNP]). Acute salt loading was induced by infusing 18% saline for 60 min into conscious, trained, chronically catheterized animals and plasma osmolality (Posm) and mean arterial pressure (MAP) were monitored. An increase in Posm was associated with a rise in [OT-RNP] and the relationship between delta [OT-RNP] and delta Posm was similar for both LE and DI rats over the first 40 min of infusion (21.6 and 19.7 fmol ml-1 mosm-1 kg-1, respectively). Although Posm continued to rise between 40 and 60 min infusion, [OT-RNP] actually fell slightly during this period in LE rats to a final elevation of 682 +/- 40 fmol/ml above initial values whereas [OT-RNP] in DI rats continued to rise to a final elevation of 1,927 +/- 288 fmol/ml above initial values at 60 min of infusion. The differences between these elevations at 60 min for LE and DI rats were highly significant (p less than 0.001). For LE rats, the increase of [OT-RNP] with Posm for the first 40 min of infusion was much greater than the increase in [VP-RNP] with the slope between delta [VP-RNP] and delta Posm being only 8.3 compared to 21.6 fmol ml-1 mosm-1 kg-1 in the case of delta [OT-RNP].(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Responsiveness of oxytocin-producing neurons to acute salt loading in rats: comparisons with vasopressin-producing neurons. 395 71


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