Effects on Acth Release of Intrapituitary Injections of Posterior Pituitary Hormones and Several Amines in the Hypothalamus

Control of Adrenocorticotrophin Secretion by Catecholamines in the Pregnant and Foetal Sheep

“…The infusion of acidified saline (9-5 ml/h, pH 3-5) into a ewe 131 days pregnant caused no significant changes in the heart rate, blood pressure, blood gas tension, pH values or plasma hormone concentrations in either the ewe or its foetus during or after the 2 h infusion. discussion The present results demonstrate that rises of plasma catecholamine concentrations within the physiological range increase the plasma ACTH concentration and this confirms some (Vogt, 1944;Sayers & Sayers, 1947;Long & Fry, 1945;McDermott et al 1950;Hiroshige et al 1968;Vernikos-Danellis, 1968;Kendall et al 1972). In the foetus rises in plasma ACTH concentration were observed with plasma adrenaline concentrations similar to those seen during hypoxaemia (Jones & Robinson, 1975).…”

“…Recently these observations have been confirmed in the rat where a rise in plasma ACTH concentration occurs in response to adrenaline injection (Kendall, Egans, Stott, Kramer & Jacobs, 1972). It has been suggested that this is in part the result of the direct action of catecholamines on the anterior pituitary (McDermott, Fry, Brobeck & Long, 1950;Hiroshige, Kunita, Ogura & Itoh, 1968) possibly through the action of a /^receptor (Vernikos-Danellis, 1968). Despite these observa¬ tions the physiological significance of plasma catecholamines in the control of ACTH secretion is difficult to assess because of the large amounts of catecholamines normally administered.…”

Diurnal Variation of Corticotropin-Releasing Activity in the Rat Hypothalamus

“…Even if this be the case, the possible maximal dose to be injected by our intrapituitary microinjection method would at best amount to approximately 4mU, as calculated back from the data of McCann and Haberland (1959) and Konig and Meyer (1967). As already reported (Hedge et al, 1966;Hiroshige et al, 1968a), this amount of vasopressin as well as oxytocin, when placed directly into the adenohypophysis, was proved quite ineffective in eliciting ACTH release. As to the biogenic amines present in the hypothalamus, daily rhythms were observed in the norepinephrine content of the rat hypothalamus (Manshardt and Wurtman, 1968) and also in the noradrenaline and histamine content in the caudate nucleus and mid-brain of the rat (Friedman and Walker, 1968).…”

“…But, the rise of serotonin content over its nadir was only 18% (Scheving et al, 1968) or at best 65 % (Friedman and Walker, 1968). Furthermore, we have already shown (Hiroshige et al, 1968a) that not only norepinephrine but also serotonin is virtually devoid of CRF-like activity when tested by our intrapituitary microinjection method. Friedman and Walker (1968) reported also that histamine content and its pattern of daily change were not influenced at all by chronic adrenalectomy.…”

Acth Release by Purified Hypothalamic CRF Preparation as Assayed by Intrapituitary Microinjection

“…Consequently, main problem in in vivo systems for assaying CRF activity in crude extracts appears to lie in the difficulties in separating the potency of CRF from that of vasopressin. Since we have already shown (Hiroshige et al, 1968b) that either of the posterior pituitary hormones, when placed directly into the adenohypophysis, is virtually devoid of CRF activity, an advantage of the direct microinjection method is apparent. As to the sensitivity of this method, comparison Endocrinol.…”