Some aspects of the effects of acute reserpine treatment on behaviour.

Hitherto behavioural investigations with reserpine have been confined to the use of very small doses, doses which weight for weight are considerably lower than those used in clinical work. Sidman (1956) used a Skinner lever pressing apparatus for investigating the effect of up to 0 1 mg./kg. reserpine on work under different reinforcement programmes. Smith, Wagman, Wagman and Riopelle (1956), investigating the effects of reserpine on conditioned avoidance behaviour in monkeys with brain lesions, used doses between 0415 and 0-37 mg./kg. However, pharmacologists have reported interesting effects with more substantial doses in a variety of species. In particular, attention can be drawn to the atypical sedation induced by the drug. Unlike other depressants of the central nervous system, e.g., barbiturates, reserpine produces no anaesthesia, as animals can always be roused by external stimulation. Further, a paradoxical behaviour and electro-encephalographic pattern appears. Rats, for example, appear chronically sedated to the observer but have an alerted E.E.G. At the same time the limbs of drugged rats can be positioned in catatonic-like postures, deep body temperature falls steeply, and the sympathetic division of the autonomic nervous system appears to be blockaded. Subsequent reports will deal with experiments designed to determine the connexion between the pharmacological and physiological properties of the drug and behaviour. The present paper is concerned with accounts of the drug concentrations and the time factors which are involved in a behavioural disturbance induced with reserpine. In order to accomplish this it was necessary to discover the course of the reserpine disturbance in the rat the onset, the duration, and the time of recovery-by employing some behavioural criterion. For this purpose two measures were employed, response latency, that is, the time taken by the rat from the moment of entry into the apparatus to when it began to run, and a locomotor time score obtained from a straight runway apparatus. It was held that latency could be taken as the time required for the rat to organize its response in a given situation. In view of the known high specificity of reserpine treatment on the central nervous system it was postulated that this measure would be adequately sensitive. Locomotor efficiency was tested by measuring the time taken by the rat to move over a fixed distance. A 100 decibel mixed frequency noise generator was used to induce running behaviour in the apparatus after a criterion latency time had been exceeded.