MODIFICATION OF THE EFFECTS OF TRANQUILIZERS IN ANIMALS TREATED WITH -METHYL-l-TYROSINE

¹ Department of Pharmacology, S.M.S. Medical College, Jaipur, India

Experiments were performed to study the effects of reserpine, chlorpromazine and meprobamate in animals with lowered tissue norepinephrine levels. In rats treated with three doses of -methyl-l-tyrosine (AMT, 80 mg/kg) over a period of 24 hr, the brain norepinephrine level was lowered by 65%. In AMT-treated animals the pharmacologic actions of reserpine and chlorpromazine, namely, hypothermia and potentiation of barbiturate hypnosis in mice as well as blockade of conditioned avoidance response of trained rats, were markedly enhanced. Meprobamate was ineffective in causing any significant effect either in control or in AMT-treated animals. The significance of these findings is discussed. Although the role of dopamine depletion cannot be ruled out since dopamine estimations were not made, it seems that the lowering of brain norepinephrine caused by reserpine, though by itself insufficient to produce sedation, contributes to reserpine's tranquilizing effect by lowering the tone of the ergotropic system of the hypothalamus.