Pharmacological manipulation of immune alterations induced by an aversive conditioned stimulus: evidence for a beta-adrenergic receptor-mediated Pavlovian conditioning process.

The effect of propranolol, a beta-adrenergic receptor antagonist, on the suppression of splenic mitogenic responsiveness induced by an aversive conditioned stimulus (CS) was evaluated in rats. Experiment 1 demonstrated that propranolol administration before presentation of the CS completely blocked the suppressive effect. In contrast, Experiment 2 showed that administration of propranolol during the training of the aversive CS had no effect on the suppressive effect of the CS in a subsequent test. These findings indicate that the release of catecholamines is responsible for the conditioned immune alteration of splenic lymphocytes. Taken further, these findings suggest that the learning of the conditioned immunomodulatory response to an aversive CS is a Pavlovian conditioning process that is not dependent on the performance of the conditioned response during training.