E. Stark

Effect of Gamma-Aminobutyric Acid (GABA) and GABA Antagonist Drugs on ACTH Release

Corticotrophin (ACTH) release has been studied in rats given intraventricular gamma-aminobutyric acid (GABA) infusions or injections of picrotoxin and bicuculline. As an index of ACTH release the cort

Effect of intraventricular glutamate on ACTH release.

Sodium glutamate infused into the 3rd ventricle is a potent stimulus of ACTH release, as shown by the rise in plasma corticosterone levels. Glutamate failed to consistently increase the plasma corticosterone level in rats with deafferentation of the medial basal hypothalamus (MBH). We suggest that intraventricular glutamate interferes with central nervous function outside the MBH and stimulates ACTH release via afferent neural pathways.

Effect of beta-endorphin on the steroid production of isolated zona glomerulosa and zona fasciculata cells.

Abstract Small doses of β-endorphin (10−11−10−5M) decrease corticosterone production of zona fasciculata cells but fail to influence steroid production of zona glomerulosa cells. 10−4M β-endorphin increases corticosterone production of both zones. The stimulating effect of ACTH on zona fasciculata corticosterone- and zona glomerulosa aldosterone production was decreased by β-endorphin (10−9−10−7M). Conclusion: β-endorphin might modulate both basal and ACTH stimulated corticosterone secretion.

The localisation of acid phosphatase activity changes in lysosomes in the adrenal zona fasciculata of intact and hypophysectomized rats following ACTH administration.

SummaryIn the cells of the zona fasciculata of intact adult rats lysosomes can be found in medium amounts, measuring 0.2–0.4 μ in diameter. After treatment with ACTH, the lysosomes in the zona fasciculata of the intact animals increase in number and size, and lysosome-lipid conglomerates are formed. In hypophysectomized animals, the lysosomes in the zona fasciculata decrease in number and size in proportion to the time elapsed. Treatment with ACTH given 2 to 4 weeks after hypophysectomy, resulted in the increase in number and size of the lysosomes. Under such circumstances lysosomes appear in conspicuously large numbers around lipid droplets, which frequently coalesce with them. The possible role of lysosomes is discussed.

Effect of alpha-MSH on the corticosteroid production of isolated zona glomerulosa and zona fasciculata cells

Abstract α-MSH (10 −9 − 6×10 −7 M) potentiates the effect of ACTH (10 −11 − 5×10 −9 M) on adrenocortical steroidogenesis decreassng ED 50 of ACTH from 220 to 183 pg/ml on zona fasciculata corticosterone-, and from 739 to 437 pg/ml on zona glomerulosa aldosterone production. α-MSH alone increases aldosterone production of zona glomerulosa cells in doses (10 −9 − 6×10 −7 M) that do not stimulate zona fasciculata corticosterone production. The response of zona glomerulosa aldosterone production to α-MSH can be characterized by a bi-phase dose-response curve.

Growth and fine structure of monolayers derived from adult rat adenohypophyseal cell suspensions

SummaryPrimary monolayer cell cultures of trypsin-dispersed adult rat adenohypophyses are capable of synthetizing deoxyribonucleic acid and are able to divide at least for 3 weeks. Most cells contain secretory granules in the absence of hypothalamic extracts. It seems possible that granules are formed which mature and are released in vitro.

The Effects of Cholinomimetic Drugs and Atropine on ACTH Release

Acetylcholine (1 and 50 mug), carbamylcholine (1 and 10 mug), and oxotremorine (10 mug) were infused into the 3rd ventricle of rats with deafferented medial basal hypothalamus (MBH); infusions failed to stimulate ACTH release as shown by the plasma corticosterone level. Implants of an atropine-fluorescein mixture (200-250 mug) inhibited the stress-induced rise of plasma corticosterone only when dye from the implant stained large portions of the median eminence and the basal hypothalamus. Atropine implants near the electrodes inhibited the rise in plasma corticosterone usually produced by electrical stimulation in the anterior hypothalamus. Atropine crystals or a 2% atropine sulphate solution placed on the median eminence blocked conduction of action potential in the hypothalamo neurohypophyseal and tubero-infundibular pathways. The evidence will be discussed for and against the participation of a cholinergic synapse (in the MBH) that activates ACTH release after stressful neural stimuli.

Evidence that the mediobasal hypothalamus is involved in serotonergic stimulation of renin secretion.

The effect of the serotonin-releasing drug parachloroamphetamine (PCA) on plasma renin activity was studied in rats 4 days after surgical lesions of the mediobasal hypothalamus, anterolateral deafferentation of the mediobasal hypothalamus, posterolateral deafferentation, or hypophysectomy. PCA increased plasma renin activity in sham-operated rats, but it failed to increase plasma renin activity in rats with mediobasal hypothalamic lesions or posterolateral deafferentation. The response to PCA was unaffected by anterolateral deafferentation and enhanced by hypophysectomy. There were no significant differences in plasma renin activity in lesioned, deafferented, and hypophysectomized rats injected with saline. The data indicate that the mediobasal hypothalamus is part of the pathway by which central serotonergic neurons affect renin secretion, and that the effect is not mediated via hormones of the pituitary gland.

Quantitative Histological Changes in the Rat Hypothalamus Following Bilateral Adrenalectomy

At 24 h after bilateral adrenalectomy, an increase in nuclear volume can be observed in the anterior centromedial cell group of the ventromedial nucleus; this increase is still present on the 7th day

Catecholamine concentration of various brain nuclei of the rat as affected by ACTH and corticosterone.

The acute effect of ACTH and corticosterone on catecholamine concentration of individual brain nuclei has been examined. ACTH significantly increased the noradrenaline (NA) content in the locus coeruleus, and decreased it in the ventromedial and arcuate nuclei. No change was observed after ACTH in the dopamine (DA) concentrations of the mentioned areas and in the catecholamine level of the mamillary body, hippocampus, medial habenular nucleus and of the pituitary. Corticosterone increased the NA content of the supraoptic nucleus and the NA and DA levels in the median eminence, while it did not affect the amine concentrations in the locus coeruleus.