A study of the role of noradrenaline in behavioral changes produced in the rat by psychotomimetic drugs.

1. LSD-25, psilocybin and JB-329 reduced the noradrenaline content of the rat hypothalamus.2. All three drugs affected the acquisition of a conditioned avoidance response, LSD-25 and psilocybin retarding and JB-329 enhancing the acquisition. With the exception of JB-329, doses affecting the acquisition of a conditioned avoidance response were lower than those required to decide hypothalamic noradrenaline concentrations. The time of peak drug effect on the acquisition of a conditioned avoidance response occurred approximately 1.5 hr after injection as opposed to 3 hr in the case of noradrenaline content.3. The amount of LSD-25, psilocybin and JB-329 necessary to elicit gross behavioural excitation was similar to the dose producing noradrenaline depletion. Here also the peak behavioural effect was detected earlier.4. Pretreatment with reserpine and alpha-MT had no effect on the intensity of gross behavioural excitation induced by LSD-25 and psilocybin but shortened the duration of the response. The excitation induced by JB-329 was abolished by reserpine pretreatment and was markedly reduced both in intensity and duration by the prior injection of alpha-MT.