PHYSIOLOGICAL DISPOSITION OF 5-METHOXYTRYPTAMINE AND ROPE CLIMBING PERFORMANCE OF RATS

5-Methoxytryptamine (5-MT) is taken up rapidly by rat tissues after IP injection (50 mg/kg) and the following peak levels (μg/g or ml of sample) were observed after 5 min: plasma, 5.3; liver, 126; skeletal muscle, 2.4; brain 0.43. Over 90% of the compound disappeared from the plasma and the tissues studied within 60 min. The compound impaired rope climbing performance of trained rats. Pretreatment of the animals with iproniazid enhanced the effect of 5-MT whereas its main (and probably only) metabolite, 5-methoxyindoleacetic acid, did not interfere with rope climbing at a dose of 75 mg/kg. 5-MT also produced marked cutaneous vasodilatation, analgesia and hindleg paralysis. All pharmacological effects lasted approximately 75 min. It is suggested that 5-MT is the pharmacological active agent and that behavioral changes observed after IP injection of the compound are mainly caused by the peripheral and little, if any, by a central action of this compound. © 1969 Springer-Verlag.