Alastair J S Summerlee

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Central injection of porcine relaxin into the lateral ventricle of water-replete rats caused a marked drinking response. Relaxin in 2 µL 0.9% saline caused a dose-dependent (range 10-50 ng), significant (P<0.01) dipsogenesis compared with saline-treated controls. There was no drinking response to <10 ng relaxin. At 10 ng relaxin ICV rats drank 4.2 ± 0.2 mL(More)
The novel finding that relaxin has an action on the brain was first published in 1984. Since then, it has been shown that exogenous relaxin affects the release of a number of hypothalamo-pituitary hormones and has a robust pressor action. In this paper, we review the accumulating evidence that relaxin affects the release of oxytocin and vasopressin by an(More)
1. Extracellular electrical recordings were taken from nine antidromically identified paraventricular units in unanaesthetized, unrestrained rats. Neuronal activity was correlated with the observed events of parturition, i.e. abdominal contractions and delivery of young or placentae. 2. The level of spontaneous activity (0.15--3.2 spikes s-1) of all nine(More)
Experiments were performed on anaesthetized, lactating rats to investigate the acute central actions of relaxin on blood pressure and vasopressin release. When compared with saline and control injections of isotonic protein extract, administration of relaxin into either the lateral or dorsal portion of the third ventricle caused a significant and sustained(More)
Experiments were done to examine whether rat relaxin is dipsogenic and whether such dipsogenic effects of rat relaxin are related to time of injection during the light-dark cycle. Female rats were fitted with a chronic intra-cerebro-ventricular (i.c.v.) cannula. Rat relaxin (2.5, 5, 10, 25, 50, or 100 ng/2 microl in 0.9% saline) was injected into the right(More)
Experiments were conducted in anesthetized rats to assess the contribution of the brain angiotensin-II system in the relaxin-induced secretion of vasopressin and oxytocin. Intravenous injection of porcine relaxin (5 micrograms) caused a significant (P < 0.05, by analysis of variance) increase in plasma concentrations of both hormones. Peak concentrations of(More)
Experiments were carried out to investigate the effects of porcine relaxin on the course of gestation and delivery in the rat. Plasma relaxin was maintained at approximately 600 nmol/l from day 19 to day 23 of gestation by i.v. infusion from chronically implanted minipumps. Relaxin significantly (P less than 0.001) prolonged the length of gestation in 17(More)
Experiments were conducted to investigate the role of the brain angiotensin system in mediating the pressor effects of porcine relaxin in anesthetized female rats. Continuous intracerebroventricular infusion of a specific angiotensin II receptor antagonist (Sar1-Ala8-angiotensin II) completely negated the pressor response to centrally administered relaxin,(More)
The role of the subfornical organ in the timing of birth in the rat was investigated. Animals with radiofrequency lesions of the subfornical organ made on day 12 of pregnancy gave birth significantly earlier (P < 0.05) than intact and control-lesioned rats. Animals with lesions made on day 19 of pregnancy gave birth within control times. In addition, the(More)
In several species the myometrium is quiescent shortly before parturition. At this time high titres of relaxin are present in the plasma and there is evidence that the hormone has a direct inhibitory action on the uterine muscle. Relaxin could also contribute to uterine quiescence by inhibiting oxytocin release. To determine whether relaxin has a central(More)