Effects Of ACTH On Conditioned Suppression: A Time And Strength Of Conditioning Analysis

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Physiology And Behavior


The effects of ACTH injections on acquisition and retention of a conditioned-suppression response were measured as a function of the time of training and the duration of the conditioned stimulus. Rats were trained 5 a.m. ± 1 hr or 5 p.m. ± 1 hr; training consisted of a single trial in which either a 10 or 60 sec tone was followed by footshock. Retention increased following a shift in time of training from a.m. to p.m. and in tone duration from 60 to 10 sec. ACTH as Corticotrophin Gel was injected before training, before testing, or before both training and testing. The facilitatory effects of the injections were selective. Retention was improved given that the injections were made before training, as opposed to before testing, and that training was conducted in the a.m. In one case, the 60 sec tone condition, the facilitatory effects of the injections before training were cancelled if the animals were also injected before testing.

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