SALICYLATE-INDUCED PHANTOM AUDITORY EFFECTS ON REINFORCED BEHAVIOR INPREWEANLING AND POSTWEANLING RATS

In two behavioral experiments, normal hearing or salicylate-induced ph antom auditory perception were investigated in young pigmented rats. T wenty-four hours prior to training in Experiment 1, 45 preweanling pup s (14-21 days of age) were exposed to continuous background noise. The y were injected with sodium salicylate or saline either before or afte r training to suppress approach responses to a lactating dam during no ise offset periods. The sequence of injection initiation affected acqu isition and extinction rates, and the oldest subjects behaved similarl y to adults reported in studies of salicylate-induced auditory effects . Adapting the task in Experiment 2 for 18 postweanling pups 32 days o f age produced greater suppression and prolonged extinction when salic ylate was administered prior to both acquisition and extinction sessio ns, whereas subjects injected with saline before training and salicyla te before extinction showed rapid recovery from suppression. The exper iments support the notion that the auditory system undergoes functiona lly important change at around 15-16 days of age.