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ROLE OF THE NEUROHYPOPHYSIS IN THE RELEASE OF ADRENOCORTICOTROPHIC HORMONE IN THE RAT

1965; Physiological Society of Japan; Volume: 15; Issue: 3 Linguagem: Inglês

10.2170/jjphysiol.15.278

1881-1396

Akira Arimura, Toyoharu YAMAGUCHI, Keiichi YOSHIMURA, Tsuyoshi IMAZEKI, Shinji Itoh,

Growth Hormone and Insulin-like Growth Factors

The role of the neurohypophysis in ACTH release mechanism was investigated in the rat by measuring changes in blood ACTH levels under various kinds of stress. A remarkable increase in blood ACTH following repeated pain stimuli of 1 second duration on the paws or injection of synthetic lysine vasopressin, 400mU./100g. i. p. or i. v., was seen in the normal intact or the sham-operated rats, while it was absent or considerably reduced 1 week after the removal of the pituitary neural lobe. Prolonged pain or laparotomy induced a marked rise in blood ACTH both in the control and the neurohypophysectomized rats, but the elevation of blood ACTH was significantly less in extent in the absence of the neural lobe. Intraperitoneal injection of histamine induced a moderate rise in blood ACTH to the same extent both in the control and the neurohypophysectomized rats. The extract of the pituitary neural lobe of the rat, in a dose of 400 milli pressor units of lysine vasopressin, induced a considerable rise in blood ACTH regardless presence or absence of the neural lobe, but was not effective in the hypophysectomized rats. Since the ablation of the neural lobe resulted in a near-complete abolishment of vasopressin's corticotropic effect, the increase in blood ACTH following injection of the neurohypophysial extract may be due to CRF stored in the neural lobe. Blood supply to the adenohypophysis was not impaired, but rather increased 1 week after the removal of the neural lobe.