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)

During suckling, anaesthetized lactating rats release regular (about every 7 min) but brief pulses of oxytocin (0.5--1.0 mu.) which produce single transient increases in intramammary pressure. Drugs which selectively impair synaptic transmission were used to determine the role of dopamine and noradrenaline in regulating this natural reflex. Diethyldithiocarbamate (100--200 mg/kg, i.v.) and alpha-methylparatyrosine (100--400 mg/kg, i.v.) which inhibit the synthesis of catecholamines both blocked the suckling-induced release of oxytocin. The milk-ejection reflex was also inhibited in a dose-dependent manner by the intravenous administration of the dopamine antagonists, fluphenazine (0.7 mg/kg), pimozide (1.4 mg/kg), cis-dupenthixol (4.5 mg/kg) and metoclopramide (6.0 mg/kg), and caused a significant inhibition P less than 0.01) of the reflex in 50% of the rats tested. The alpha-adrenoceptor antagonist phenoxybenzamine (1.4 mg/kg) was similarly effective. Dopamine (40 micrograms), bromocriptine (10 micrograms), apomorphine (100 micrograms), noradrenaline (10 micrograms) and phenylephrine (2 micrograms) injected into the cerebral ventricles evoked a sustained release of oxytocin which produced multiple increases in intramammary pressure; isoprenaline (4 micrograms) was ineffective. The release of oxytocin evoked by dopamine and noradrenaline was prevented by cis-flupenthixol and phenoxygenzamine respectively. None of the drugs used affected the mammary sensitivity to exogenous oxytocin nor were their actions modified by pretreatment with propranolol (1 mg/kg). The results suggest that the neural pathway for the reflex release of oxytocin during suckling in the rat contains both dopaminergic and noradrenergic synapses, the latter acting through alpha-adrenoceptors and being distal in the pathway to the dopaminergic component.
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PMID:Dopaminergic control of oxytocin release in lactating rats. 4 80

The ultrastructure and the spontaneous and drug-induced contractility of the testicular capsule of 18 boars were investigated. Isometric recordings were obtained in vitro using strips of the tunica albuginea isolated from various regions of the testis. Maximal contractile activity was found in the strips of the posterior border of the testis, in which the histological studies (light and electron microscopy) showed abundant typical smooth muscle cells distributed in layers parallel to the testicular long axis. These cells were largely aggregated in the inner layer of the testicular capsule, which displayed contractile activity similar to that of the entire tunica albuginea. The outer layer of the tunica albuginea was almost totally devoid of smooth muscle fibres and showed little or no contractility. The spontaneous contractions were rhythmic and exhibited an amplitude of 20--70 mg and a frequency of 5--30 contractions/10 min. Norepinephrine, acetylcholine and oxytocin all produced an increase of the contractility of the tunica albuginea, consisting mainly in a rise of the tone.
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PMID:Studies on the contractile activity and ultrastructure of the boar testicular capsule. 51 9

Electromyograms were obtained from three different locations on the uterus of conscious, unrestrained rats during the 4 day estrous cycle. Intrauterine pressure changes were monitored simultaneously by means of indwelling intraluminal balloons (vol. 0.02 to 0.05 ml.). Electrical activity consisted of bursts of action potentials that were usually initiated at either end of the uterus. Propagated burst activity gave rise to cyclic intrauterine pressure changes, whereas bursts appearing at one electrode only did not elicit any measurable contractions. The rate of intrauterine pressure development depended on the propagation velocity, whereas the tension achieved was related to the duration of burst activity. All three parameters of electrical activity studied, namely, the duration and frequency of spike bursts, as well as their rate of propagation, varied significantly during the cycle. Regional differences were also subject to cyclic variations; thus, in proestrus the bursts originated predominantly at the cervical end, whereas in diestrus they were usually initiated at the ovarian end. Oxytocin stimulated the frequency and duration of bursts along the whole uterus and elicited corresponding changes in intrauterine pressure. Response to oxytocin was dose dependent and modified by cycle stage. Norepinephrine caused a transient prolongation of burst activity that was not dose dependent; epinephrine had a marked dose-dependent inhibitory action. The response to catecholamines did not vary significantly during the cycle. The variations in electrical and mechanical activity were characteristic for each stage of the ovarian cycle and could be correlated with the well-known hormonal changes. High circulating estrogen levels in proestrus are associated with infrequent but rapidly propagated spike bursts, whereas low levels in estrus are associated with frequent and sometimes nonpropaged bursts. The rise in plasma estrogen in diestrus coincides with a decrease in the frequency of burst activity, and the elevated progesterone levels are probably causally related to the significant drop in propagation velocity and the increase in duration of bursts observed in diestrus. These findings are consistent with the concept that estrogen withdrawal activates the estrogen-primed, quiescent myometrium, and that progesterone has an effect similar to that of estrogen withdrawal--at least in the rat.
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PMID:Electrical and mechanical activity of rat uterus in vivo during the estrous cycle. 56 83

The administration of 5 I. U. oxytocin (by quick infusion) or of 5 I. U. vasopressin-lysine (intramuscularly) to healthy subjects was followed by a significant decrease in the plasma non-esterified fatty acid level. We regard this as evidence of inhibition of basal lipolysis in the adipose tissue. Vasopressin also completely blocked an increase induced in the plasma non-esterified fatty acid level by activating hormone-sensitive lipase in the adipose tissue by the infusion of 0.5 mg noradrenaline.
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PMID:Inhibition of lipolysis by oxytocin and vasopressin. 61 48

To determine the precise localization of the pacemaker in the renal pelvis of the unicalyceal rabbit kidney, the spontaneous activity of muscle strip preparations was investigated in vitro. (1) The highest frequency of spontaneous contractions was found in the most intrarenal part of the renal pelvis. (2) The frequency diminished from the most intrarenal parts to the pyeloureteral junction. (3) No spontaneous activity was observed in ureter preparations; even adrenaline, noradrenaline, acetylcholine and oxytocin did not start any contraction. In the pyeloureteral system the cells with the highest spontaneous frequency will act as a pacemaker. Cells with a less frequent activity can only work as secondary or latent pacemakers.
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PMID:Pacemaker localization in the renal pelvis of the unicalyceal kidney. In vitro study in the rabbit. 65 74

The effects of norepinephrine, phentalamine, oxytocin, vasopressin, several prostaglandins, and indomethacin on the spontaneous motility of isolated guinea pig cauda epididymidis were explored. Phentolamine and indomethacin reduced the isometric peak tension of spontaneous epididymal contractions. Phentolamine also depressed the frequency. Both findings suggest that catecholamines and endogenous prostaglandins are in some way regulators of the spontaneous motility of the cauda epididymidis. Norepinephrine resulted in the development of a distinct, sustained, tonic contraction without phasic activity, whereas prostaglandins E1, E2, and F2 alpha elicited a tonic increase accompanied by frequent, superimposed, phasic contractions. Both oxytocin and vasopressin comparably enhanced epididymal motility, producing contractile responses similar to those observed with prostaglandins. Since the epididymal contractions can influence the time spent by spermatozoa in passing through the ductus epididymidis, the above-mentioned compounds could play an important role in spermatozoal transport via modulation of epididymal contractile activity. In addition, such naturally occurring substances might regulate the release of sperm from the last portion of the epididymis into the ductus deferens.
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PMID:Physiologic and pharmacologic studies on the motility of isolated guinea pig cauda epididymidis. 80 41

1 Thirty-three amino acids were applied separately in concentrations of 2 to 10 mM to guinea-pig uterine horns in vitro at pH 7.4. About half the acids regularly produced contractions.2 Glycine and the straight-chain L-alpha-amino acids up to norleucine were active (longer ones not tested); D-isomers were less potent or inactive in these concentrations. The omega-amino acids gamma-aminobutyric acid (GABA) and delta-aminovaleric, and the alpha,omega-diamino acids L-alpha,beta-diaminopropionic and L-alpha,gamma-diaminobutyric were active, whereas others of similar chain-length such as beta-alanine and lysine were not. The diacidic acids, glutamic and homocysteic, were more active than the amido-amino acids, glutamine and asparagine. Histidine and phenylalanine showed little or no activity.3 The use of appropriate blocking agents indicated that the responses to representative acids were not mediated by histamine, 5-hydroxytryptamine, acetylcholine, noradrenaline or by prostaglandins. Attempts to block the actions of glycine and GABA with strychnine, thebaine, picrotoxin, bicuculline or tetramethylenedisulphotetramine (TETS) were unsuccessful.4 When some of the acids that were spasmogenic at 2 to 10 mM were applied at sub-spasmogenic doses, they transiently potentiated other spasmogens such as oxytocin or acetylcholine. This effect was also shown by a mixture of amino acids at approximately the normal plasma concentrations.5 There is some similarity between the spasmogenic activities of different amino acids and their known abilities to depolarize neurones.
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PMID:Spasmogenic and potentiating actions of some amino acids on the guinea-pig myometrium. 92 51

1. The rat hypothalamus (containing the supra-optic nuclei, paraventricular nuclei, median eminence and proximal pituitary stalk) has been incubated in vitro and shown to be capable of releasing the neurohypophysial hormones, oxytocin and arginine vasopressin, at a steady basal rate about one twentieth that of the rat neural lobe superfused in vitro. 2. The hypothalamus and neural lobe in vitro released both hormones in a similar arginine vasopressin/oxytocin ratio of about 1-2:1. However, when release was expressed relative to tissue hormone content, the hypothalamus was shown to release about three times as much arginine vasopressin and six times as much oxytocin as the neural lobe. 3. Dopamine in a concentration range of 10(-3)-10(-9)M caused graded increases in hormone release from the hypothalamus in vitro to a maximum fivefold increase over preceding basal levels. The demonstration that apomorphine also stimulated hormone release whereas noradrenaline was relatively ineffective suggested that a specific dopamine receptor was involved. A separate cholinergic component in the release process was indicated by the finding that acetylcholine stimulated release to a maximum fivefold increase in concentrations of 10(-3)-10(-9)M. 4. The fact that the isolated hypothalamus can be stimulated by dopamine and acetylcholine to release increased amount of oxytocin and arginine vasopressin raises the question of the origin and fate of the hormones released in this way. The possibility that they could be released into the hypophysial portal circulation from median eminence to affect the anterior lobe of the pituitary is discussed. 5. In similar doses, both dopamine and noradrenaline injected into the lateral cerebral ventricles of the brain of the anaesthetized, hydrated, lactating rat caused the release of arginine vasopressin and oxytocin. Apomorphine release both hormones but at a higher dose level and to less effect than the catecholamines. 6. The hormone release induced in vivo by dopamine could be prevented by the prior administration of haloperidol or phentolamine and these antagonists were equally effective in blocking the hormone release due to noradrenaline. The involvement of a specific dopamine receptor was more clearly implicated by the use of pimozide which completely inhibited the hormone release due to dopamine and apomorphine but not that due to noradrenaline. 7. It is suggested that the release of neurohypophysial hormones can be stimulated via a dopaminergic nervous pathway in addition to a cholinergic one. The possibility that the osmoreceptor mechanism for the release of antidiuretic hormone from the neural lobe of the pituitary may involve such a dopaminergic pathway is discussed.
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PMID:The effect of dopamine on neurohypophysial hormone release in vivo and from the rat neural lobe and hypothalamus in vitro. 98 83

1 The responses of the smooth muscle of the capsule and blood vessels of the isolated, blood-perfused spleen of the dog to angiotensin, oxytocin and vasopressin have been investigated and compared to the actions of the catecholamines, adrenaline and noradrenaline.2 Increasing doses of each of the three polypeptides cause graded increases in splenic vascular resistance and reductions in spleen volume.3 Doses of the polypeptides which evoked increases in splenic vascular resistance not significantly different from increases produced by chosen doses of each catecholamine caused significantly smaller reductions in spleen volume.4 The time-course of action of the polypeptides on the splenic vascular smooth muscle is different since the time to 50% recovery from vasopressin is highly significantly longer than that for equieffective doses of either angiotensin or oxytocin.5 Phenoxybenzamine, in a dose which almost blocked the actions of the catecholamines, increased the responses of the vascular and capsular smooth muscle to oxytocin, vasopressin and angiotensin. This increase was not observed with another alpha-adrenoceptor blocking agent, phentolamine.6 The significant species variation in the responses of the smooth muscle of the spleen to polypeptides and catecholamines are discussed and the results are considered in the context of the possible physiological roles of the polypeptides in haemorrhage.
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PMID:The responses of the isolated, blood-perfused spleen of the dog to angiotensin, oxytocin and vasopressin. 114 10

The spontaneous motility of ovaries isolated from guinea pigs in early and late proestrus and estrus was explored. The influences of oxytocin, prostaglandin F2alpha (PGF2alpha), and adrenergic agonists and antagonists were also studied. Spontaneous ovarian isometric developed tension (IDT) and rate of contractions (RC) were greater in late proestrus than in early proestrus or estrus. Furthermore, in late proestrus, oxytocin and PGF2alpha induced ovarian motilities of comparable magnitude and significantly greater than those elicited in other stages of the cycle. Norepinephrine and phenylephrine either failed to alter or inhibited IDT and RC of ovaries in estrus, but stimulated motility in the presence of propranolol. The depressive influence of norephinephrine upon the IDT of ovaries in early proestrus was not seen in late proestrus, when the neurotransmitter was clearly stimulating. The hormonal status of guinea pigs seems to influence spontaneous ovarian motility as well as pharmacologic reactivity to several agents, including those presumably acting upon alpha- and beta-adrenergic receptors.
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PMID:Physiologic and pharmacologic studies on the motility of isolated guinea pig ovaries. 116 89


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