Habituation of the head-poke response: effects of an amphetamine-barbiturate mixture, PLG and fenfluramine.

A test situation was developed in which the effects of drugs on habituation of exploratory behavior (head-poke responses) could be assessed independently of their effects on general activity (locomotion and rearing). Habituation, spontaneous recovery from habituation and stimulus specificity of habituation were studied. An amphetamine-barbiturate mixture attenuated habituation of the head-poke response without influencing general activity. Pro-Leu-Gly-NH2 (PLG), an oxytocin fragment, increased locomotor activity and did not alter the course of habituation of the head-poke response. Since exploratory behavior and general activity can be pharmacologically dissociated in the test situation used, it is concluded that the test situation is suitable for studying the effects of drugs on habituation of exploratory behavior. The amphetamine-barbiturate mixture did not influence the stimulus specificity of habituation of the head-poke response. Fenfluramine however increased the effects of stimulus change on the head-poke response while not influencing habituation of this response. These results show that habituation and stimulus specificity of habituation of exploratory behavior can be pharmacologically dissociated.