BLOOD ACTH: EFFECTS OF ETHER, PENTOBARBITAL, EPINEPHRINE AND PAIN1

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Abstract
The exogenous test for ACTH release, analysis of blood ACTH in a recipient hypophysectomized rat, provides information on the rapid changes in blood ACTH which may follow application of a stimulus. The endogenous test, analysis of ACTH release by adrenal ascorbic acid depletion in the stimulated animal, fails to uncover these dynamic changes. A painful stimulus markedly elevates blood ACTH within a few minutes of application. Elevated blood levels persist during 30 minutes of intermittent painful stimulation. Ether first excites, then inhibits ACTH release. Penotobarbital exhibits only a depressant action. The excitatory action of ether is blocked by decerebration and by destruction of the median eminence area of the hypothalamus. The excitatory action of epinephrine is manifest in the decerebrate but not in the median eminence lesion rat. Since ether and pentobarbital depress the brain stem reticular system, it is reasonable to speculate that the action of these two agents in inhibiting ACTH release involves this multisynaptic conduction system. The reduction by pentobarbital of blood ACTH below the resting level characteristic of undisturbed adrenalectomized rats suggests that stimuli encountered in everyday existence such as light, sound and touch, exert a tonic action on the pituitary to maintain a low rate of release of ACTH.