Hormone Secretion In Rats Research Articles

Insulin and growth hormone secretion in rats with ventromedial hypothalamic lesions maintained on restricted food intake.

Adult female rats were trained for one week to consume a subnormal amount of food (12 gm.) in two one-hour feeding sessions per day: 4 gm. between 8 and 9 a.m. and 8 gm. between 6 and 7 p.m. At the end of the training period the animals were subjected to either bilateral electrolytic destruction of the ventromedial hypothalamus (VMH) or to a sham operation. The restricted feeding regime was continued for forty-eight hours postoperatively, when comparative studies were made. Plasma insulin response to intravenous Glibenclamide was greater in the rats with VMH lesions than in the pair-fed, sham-operated controls. The former rats also exhibited decreased initial plasma glucose levels, degranulation of the beta cells and reduced pancreatic insulin content. In addition to marked islet enlargement, similar though more severe signs of islet hyper-function were observed in rats with VMH lesions fed ad libitum, which became hyperphagic immediately after the operation. VMH lesions did not significantly affect the plasma and pituitary levels of growth hormone (GH). The restricted feeding regime, however, caused an increase in plasma GH, responsiveness to hypoglycemic stimulation and a tendency to decreased pituitary GH content both in injured and sham-operated rats. These findings indicate that VMH lesions per se enhance the responsiveness of the pancreatic islets to insulin secretory stimulation independent of changes in food intake, meal size and meal frequency. The resulting hyperinsulinism might play an essential role in the occurrence of hypothalamic hyperphagia and obesity following VMH injury. In hyperphagic rats with VMH damage, the islet stimulation is magnified, possibly due to the combination of a direct hypothalamic effect plus the secondary effect of increased food intake. Defective secretion of GH does not appear to be primarily involved in the induction of the hypothalamic syndrome.

Chapter 26. The Cannabinoids: Therapeutic Potentials

A review of the therapeutic potentials of the cannabinoids is presented. With respect to the antifertility aspects of cannabinoids, 2 mg delta 9-THC suppressed luteinizing hormone secretion in rats and 2 and 3 mg/kg resulted in a deterioation of male sexual performance. A new chapter in marijuana research was opened in 1964 with the identification of delta 9-tetrahydrocannabinol as the active ingredient. Antiedema, analgesic, antipyretic, antiinflammatory, antifertility, antiepileptic, anticonvulsant, antihypertensive, cardiotonic, pulmonary, and antidepressant effects along with potentiation of barbiturates and analgesics are reviewed leading one to the conclusion that marijuana is "a drug for all reasons". During the past decade many investigators have pursued the possibility of modification of the delta 9 structure to delineate activities. 1 compound, Abbott 40656, SP106, a water-soluble benzopyran derivative is presently under Phase 1 clinical evaluation as a sedative-hypnotic.

Effect of repeated administration of excess iodide on thyroid hormone secretion in rats, with special reference to the escape from the iodide effect.

Two hundred μg to 2 mg KI were injected every 12 or 24 hr ip for up to 7 days in rats, and thyroidal radioiodine release and the increase of intracellular colloid droplet formation induced by TSH were measured to assess the effect of repeated injections of excess iodide. A single injection of excess iodide blocked thyroidal radioiodine release, but this effect continued for about 34 hr in spite of repeated injections of excess iodide. An increase of colloid droplet formation induced by TSH was blocked by excess iodide, but 2 to 3 injections of excess iodide were required to produce maximal inhibition. This iodide effect on colloid droplet formation disappeared almost completely by the Sth day of iodide administration. However, a huge dose of KI again depressed the increase of TSH-induced colloid droplet formation in the thyroid which had escaped from the inhibitory effect of excess iodide. It is suggested that excess iodide blocks the release of thyroid hormone in rats, but only for a short time. (Endocri...

Regulation of Growth Hormone Secretion in Rat

Regulation of Growth Hormone Secretion in Rat

Role of catecholamines in the control of melanocyte-stimulating hormone secretion in rats.

Suppression of the adrenergic system by injection of reserpine (0.2 mg/kg for 2 days) into male rats resulted in a decrease of the pituitary MSH content. The same effect was observed 30, 60, or 120 mi

Thyrotrophic hormone secretion in rats after partial or total interruption of nueral afferents to the medial basal hypothalamus.

Neural connections to the medial basal hypothalamus (MBH) were partially or totally transected with a small knife. Ovulation, ovarian compensatory hypertrophy (OCH) and hypophysial response to castration were studied i n the same animals. After complete deafferenta-tion of the MBH, ovulation did not occur. Transection of the posterior and posterolateral connections to the MBH did not interfere with ovulation. If, in addition, lateral and superior affer-ents were also interrupted, 8 animals out of 12 still ovulated. Ovulation did not occur in 18 rats when only the anterior connections to the MBH were interrupted by an extended frontal cut just posterior to the optic chiasm, reaching 1.5 mm lateral from midline and extending from the base of the brain to the paraventricular nuclei above. A small frontal cut at the same level but extending only 0.6 mm lateral from midline was ineffective in blocking ovulation. When placed 1.5 mm behind the level of the optic chiasm this small frontal cut interfered with ovul...

Adrenocorticotrophic Hormone Secretion in Rats after Partial or Total Deafferentation of the Medial Basal Hypothalamus

Adrenocorticotrophic Hormone Secretion in Rats after Partial or Total Deafferentation of the Medial Basal Hypothalamus