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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of prolactin or oxytocin on milk secretion and the permeability of the mammary epithelium have been investigated in rabbits. 2. Milk yield was increased by prolactin treatment in late (25-28 days) but not in established (11-14 days) lactation. 3. Prolactin treatment increased milk [lactose] and [K] and decreased [Na] and [Cl] in late lactation, and thus reversed the normal changes in late lactation, but had no significant effect in established lactation. 4. [14C]sucrose movements from blood to milk were significantly decreased to levels characteristic of established lactation, following prolactin treatment in late lactation. No significant effect was evident with treatment in established lactation. Na and Cl movements showed similar trends. 5. It is suggested that prolactin in some way affects paracellular movements of ions and small molecules like lactose across the mammary epithelium, and that this mechanism is responsible for the changes in the composition of the aqueous phase of milk. 6. Immediately following a single dose of 100 m-u. oxytocin no significant effects on milk composition were evident but after 1 u. milk [Na] and [cl] were significantly increased. 7. Twenty-four hr after 1 u. oxytocin, milk [Na] and [cl] were decreased while [K], [lactose], [fat] and [protein] were increased. 8. During an I.V. infusion of oxytocin milk [Na] and [Cl] increased while [K] and [lactose] decreased. The passage of [(14)C]sucrose, 24Na and (36)Cl from blood to milk also increased. 9. These effects of oxytocin are discussed in relation to the permeability of the mammary epithelium and the pathways for ion movements, and to other studies on milk composition in the rabbit involving the administration of oxytocin to aid in the evacuation of milk.
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PMID:The effects of prolactin and oxytocin on milk secretion and on the permeability of the mammary epithelium in the rabbit. 121 26

Certain neuropeptides can facilitate lordosis by acting on midbrain periaqueductal gray (PAG) in estrogen-primed female rats. Here, we investigated responses of individual PAG neurons in vitro, to five neuropeptides: substance P (SP), luteinizing hormone-releasing hormone (LHRH), prolactin (PRL), oxytocin (OT), and thyrotropin-releasing hormone (TRH). Substance P, OT, and TRH excited spontaneous activity of PAG neurons through neurotransmitter-like actions in a dose-dependent manner, whereas LHRH and PRL virtually never affected PAG neurons this way. Oxytocin acted through oxytocin receptors located on the recorded PAG neurons, since excitatory actions of OT were 1) not abolished by synaptic blockade, 2) mimicked by the OT-specific agonist [Thr4, Gly7]OT but not by arginine vasopressin, and 3) blocked by the OT-specific antagonist [d(CH2)5,Tyr(Me)2,Orn8]vasotocin. Although LHRH had no neurotransmitter-like action on spontaneous activity of PAG neurons, it, as well as SP, could modulate responses of some dorsal PAG neurons to GABAA and GABAB agonists or norepinephrine. Neuromodulatory actions of LHRH and SP could help facilitate lordosis through PAG neurons.
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PMID:Effects of lordosis-relevant neuropeptides on midbrain periaqueductal gray neuronal activity in vitro. 128 9

This study was undertaken to examine whether several of the hormones that can be released by activation of serotonin receptors will be affected by long-term cocaine administration. Male rats received cocaine injections (15 mg/kg, IP) twice daily for 7 days. Forty-two hr after the last cocaine injection, the rats were challenged with increasing doses (0, 1, 5, 10 mg/kg, IP) of the 5-HT1/5-HT2 agonist MK-212 (6-chloro-2-[1-piper-azinyl]-pyrazine). The following observations were made: (1) cocaine reduced the rate of body weight gain; (2) cocaine inhibited the stimulatory effect of MK-212 on plasma vasopressin, oxytocin, and prolactin concentrations and on plasma renin activity and concentration; (3) cocaine did not inhibit the stimulatory effect of MK-212 on plasma ACTH or corticosterone concentrations. The data indicate that a wide-spectrum 5-HT (serotonin) agonist such as MK-212 can reveal differential neuroendocrine responses. This effect could be related to cocaine-induced changes in the different 5-HT receptor subtypes that regulate the secretion of these hormones.
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PMID:Effect of cocaine injections on the neuroendocrine response to the serotonin agonist MK-212. 133 9

Endocrine responses to the serotonin (5-HT) 5-HT1C/5-HT2 agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) were utilised to evaluate cocaine-induced alterations in postsynaptic 5-HT receptor function. Rats received cocaine HCl (0, 5 or 15 mg/kg i.p.) twice daily for 7 days. Effects of DOI (0, 0.5, 2 or 10 mg/kg i.p.) on plasma adrenocorticotropic hormone (ACTH), corticosterone, prolactin, oxytocin and renin concentrations were assessed 42 h after the final cocaine injection. DOI dose dependently increased the plasma concentrations of each hormone. Cocaine potentiated the DOI-induced elevations of plasma ACTH, corticosterone and prolactin concentrations. In contrast, the oxytocin response was reduced, and the renin response was unaltered by cocaine exposure. The data suggest that 5-HT2 receptor-mediated responses for ACTH, corticosterone and prolactin secretion become supersensitive following repeated cocaine. In contrast, the 5-HT2 receptor-mediated response for oxytocin secretion is subsensitive. The cocaine-induced changes in postsynaptic 5-HT receptor function are likely a consequence of deficits in the function of 5-HT nerve terminals, that we have documented previously.
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PMID:Repeated cocaine modifies the neuroendocrine responses to the 5-HT1C/5-HT2 receptor agonist DOI. 133 68

There is a great variation in body weight loss during lactation among primiparous sows fed a standard diet that is adjusted based on the number of piglets nursed and the maintenance requirements. Energy and protein catabolism is more pronounced during the first 1 to 3 weeks of lactation and sows with low weight loss recover earlier from their negative energy balance during lactation than sows with high weight loss. Using continuous blood collection a decrease in plasma levels of oxytocin, prolactin, and insulin, and an increase in plasma levels and no of LH pulses during lactation were demonstrated. Prolactin levels gradually increased in response to each suckling while only 40-50% of recorded sucklings induced a significant rise in plasma oxytocin. Following a 24-h fast during lactation, levels of prolactin were very low but increased rapidly after refeeding. Even plasma levels of insulin and glucose decreased to very low levels during fasting, but the release of LH was similar before and after refeeding. Weaning resulted in decrease in plasma levels of prolactin and increase in plasma levels and no. of LH pulses. Plasma levels of cortisol showed a diurnal pattern of change which disappeared on the day of weaning. In response to weaning plasma levels of glucagon and gastrin decreased, whereas insulin and somatostatin increased. At weaning sows with low weight loss during lactation had higher plasma insulin and lower plasma cortisol levels than sows with high weight loss, but no differences in levels or no. of LH pulses were observed between the two groups of sows.
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PMID:Metabolic and reproductive hormones during lactation and the post-weaning period in sows. 134 70

Several classes of drugs that modify serotonin (5-HT) neurotransmission are either currently used, or are being evaluated for their potential use in the treatment of anxiety, schizophrenia, and depression. 5-HT1A agonists are considered potential anxiolytics, while some atypical antipsychotics are potent 5-HT2 antagonists (and also have modest dopamine D2 affinity). Furthermore, there is a diverse group of serotonergic drugs that may be effective antidepressants. Secretion of ACTH, corticosterone/cortisol, prolactin, renin, oxytocin and vasopressin are stimulated by activation of different 5-HT receptor subtypes, while other neurotransmitter receptors also influence the secretion of these hormones. We compared the receptor binding profiles of 5-HT anxiolytics, antipsychotics and antidepressants with their endocrine effects. These comparisons could aid in understanding both the therapeutic and side effects of these drugs.
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PMID:Endocrine and receptor pharmacology of serotonergic anxiolytics, antipsychotics and antidepressants. 135 27

The administration of thyrotrophin-releasing hormone (TRH) causes a variety of dopamine-related biological events. To understand the specific role of TRH on rat hypothalamic dopamine neurones, we examined the in-vivo effects of intraventricular (i.c.v.) infusion of TRH on the release and synthesis of prolactin in the rat pituitary gland and on the changes in binding of [3H]MeTRH and dopamine turnover rates in rat hypothalamus. We have also examined the in-vitro effects of TRH on the release of [3H]dopamine from dispersed tuberoinfundibular dopamine neurones. Female rats were treated with i.c.v. infusions of 1 mumol TRH/1 daily for 1, 3 and 7 days using Alzet osmotic pumps. Following 7 days of treatment the serum prolactin concentrations were significantly decreased. A reduction in hypothalamic TRH-binding sites (Bmax) was also apparent but the dissociation constant (Kd) was unaffected. Northern blot analysis of total RNA isolated from the pituitary glands of control animals using 32P-labelled prolactin cDNA as a probe indicated the presence of three species of prolactin gene transcripts of approximately 3.7, 2.0 and 1.0 kb in size, and these were decreased by TRH treatment. We examined the turnover rate of dopamine in the rat hypothalamus when TRH was administered i.c.v. for 7 days. There was a significant increase in 3,4-dihydroxyphenylacetic acid/dopamine ratio with TRH treatment. Moreover, exposure to TRH stimulated [3H]dopamine release from rat tuberoinfundibular neurones in a time- and dose-dependent manner. Dopamine receptor antagonists such as SCH23390 and (-)sulpiride, and other neuropeptides such as vasoactive intestinal peptide and oxytocin did not affect TRH-stimulated [3H]dopamine release.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Intraventricular administration of thyrotrophin-releasing hormone (TRH) suppresses prolactin secretion and synthesis: a possible involvement of dopamine release by TRH from rat hypothalamus. 135 20

The effects of intracerebroventricularly (i.c.v.) administered histaminergic receptor antagonists on plasma levels of vasopressin, oxytocin, prolactin and adrenocorticotrophic hormone (ACTH) after fear-related emotional stress were investigated in the male rat. Pyrilamine, a histaminergic H1-receptor antagonist did not significantly alter the suppressive vasopressin or the facilitative prolactin response to nonassociatively applied emotional stress. On the other hand, i.c.v. administered ranitidine, a histaminergic H2-receptor antagonist, blocked these responses to stress. Pyrilamine again did not significantly change the suppressive vasopressin response to the associatively applied emotional stress. However, the drug attenuated the prolactin response slightly but significantly. Ranitidine blocked the suppressive vasopressin and the facilitative prolactin responses to the associatively applied emotional stress, but the drug did not change the facilitative oxytocin or ACTH response to the stress. Suppression of motor activity during the associatively applied emotional stress was not significantly changed by either of these antagonists. These results suggest that histaminergic H2 receptors are selectively involved in the neural pathways which mediate the suppressive vasopressin and the facilitative prolactin responses to fear-related emotional stress.
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PMID:A histaminergic H2-receptor antagonist, ranitidine, blocks the suppressive vasopressin response to fear-related emotional stress in the rat. 136 4

Immunocytochemical localization of neuropeptides (beta-endorphin, substance P, arginine vasopressin, oxytocin), pituitary hormones (adrenocorticotropin, prolactin, growth hormone, follicle stimulating hormone (FSH), gonadal inhibin, gastrin, and human chorionic gonadotrophin (hCG)) was carried out in marmoset testis during development. Both intensity of immunostaining and distribution of these peptides in testicular compartments viz. seminiferous tubules and Leydig cells changed dramatically during development. In vitro biosynthesis of inhibin and FSH was increased by hCG, whereas prolactin (5 micrograms) and prostatic inhibin peptide suppressed the synthesis of these hormones.
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PMID:Immunocytochemical localization of bioregulatory peptides in marmoset testes. 138 Feb 34

Milk flow in nine primiparous cows with disturbed milk ejection (D) and in six corresponding control animals (C) with normal milk removal was recorded during machine milking and blood samples were taken before and during milking to determine plasma oxytocin, vasopressin, prolactin, cortisol, oestradiol-17 beta, luteinizing hormone, progesterone and beta-endorphin concentrations. Manual teat stimulation before milking lasted for 1 min. After milk flow had stopped, air was blown into the vagina for 2 min. When milk flow had stopped again, 1 i.u. oxytocin and finally 10 i.u. oxytocin were injected to remove residual milk. During and after teat stimulation, oxytocin remained basal in D, but increased in C, whereas prolactin increased in both groups. While 94% of total milk was obtained in C during this period, only 9% could be removed from D, indicating lack of alveolar milk ejection. During vaginal stimulation, oxytocin increased transiently in D and more than by teat stimulation in C. This allowed the removal of 75% of milk in D, whereas almost no more milk was available in C. After oxytocin injections, 3 and 16% of residual milk were obtained in C and D respectively. Basal oestradiol-17 beta concentration was higher in D than in C (11.6 and 2.0 ng/l respectively), whereas beta-endorphin level was lower (24.1 and 86.6 micrograms/l respectively). Basal concentration of luteinizing hormone and progesterone, and concentration of cortisol and vasopressin before and during milking were comparable in C and D. We conclude that in cows with disturbed milk ejection afferent nervous pathways to the hypothalamus were intact, because prolactin was released by teat stimulation. However, oxytocin was only released by vaginal stimulation, i.e. milk ejection was centrally inhibited during teat stimulation.
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PMID:Aetiology of disturbed milk ejection in parturient primiparous cows. 145 33


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