The effect of adrenaline, tyramine and guanethidine on two-way avoidance conditioning and on pseudoconditioning

Adrenaline (0.5 mg/kg) or guanethidine (10 mg/kg) given i.p. depressed performance of pseudoconditioned shuttle responses by rats. In a previous paper it had been shown that tyramine (5 mg/kg) had an opposite effect (Izquierdo, 1974a). Pre-trial administration of any of the three drugs also depressed two-way avoidance conditioning. Following posttrial administration, only guanethidine had a deleterious effect on retention. Since none of these drugs is believed to reach the brain in significant amounts following systemic injection, the present results suggest that peripheral factors may influence both conditioned and pseudoconditioned shuttle behavior.