Pituitary-adrenal influences on the acquisition of excitatory and inhibitory conditioned responses in rats

Abstract

In Experiment 1, groups of hypophysectomized, adrenal demedullated, adrenalectomized, and sham-operated rats received either no preexposure treatment or preexposure to unsignaled electric shock. All groups then received CER conditioning in which a 3-min white noise stimulus was repeatedly paired with an electric shock UCS. Among the groups in the nopreexposure condition, only adrenalectomized rats showed retarded acquisition of the CER. All the groups preexposed to electric shock acquired the CER at the same rate, but when compared to their no-preexposure counterparts showed attenuation of CER conditioning. These findings indicated that the hormones of the pituitary-adrenal system are not important for the UCS preexposure phenomenon obtained with CER conditioning. Experiment 2 examined the rate of acquisition of an inhibitory conditioned response in hypophysectomized, adrenal demedullated, adrenalectomized, and sham-operated rats. Hypophysectomy, and to a lesser degree adrenalectomy, impaired the acquisition of an inhibitory condition response relative to sham-operated controls and adrenal demedullated rats. These findings were discussed in terms of pituitary-adrenal influences on avoidance learning in rats. © 1979, Psychonomic Society, Inc.. All rights reserved.