Effect of Intraventricular Administration of Adrenergic Drugs on the Adrenal Venous 17-Hydroxycorticosteroid Response to Surgical Stress in the Dog

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Abstract
The effect of the administration of several adrenergic agents into the third ventricle of the brain on the adrenal venous 17-hydroxycorticosteroid output in response to laparotomy and intestinal manipulation was studied in dogs. The catecholamines, L-norepinephrine, dopamine, and L-iso-proterenol, inhibited the 17OHCS response to stress when administered intraventricularly in total doses of 5 mg. D-Norepinephrine inhibited the 17OHCS response to a much lesser degree and the catecholamine metabolite, vanillylmandelic acid, failed to alter the 17OHCS response. Intraventricular administration of systemically-inerfective dosages of either the catecholamine precursor, L-dopa, or the monoamine oxidase inhibitor, α-ethyltryptamine, inhibited the 17OHCS response to laparotomy. Tyramine, a drug that releases catecholamines from nerve endings, inhibited the 17OHCS response when administered intraventricularly, but not when given systemically in the same or a 5-fold higher dosage. The minimum effective dose of tyramine required to inhibit the 17OHCS response was decreased by prior treatment of dogs with the monoamine oxidase inhibitor, pargyline. L-Isoproterenol, tyramine, and α-ethyltryptamine inhibited the 17OHCS response to surgical stress while decreasing both systolic and diastolic blood pressure. These data support our previously presented hypothesis that a central adrenergic neural system inhibits ACTH secretion in dogs.

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