Selective sensitization induced by lithium malaise and footshock in rats

Abstract

Following exposure to an aversive stimulus, Sprague—Dawley rats were allowed to choose between a novel and a familiar stimulus presented contingent upon licking a drinking spout. Rats pretreated with footshock showed reduced preference for a novel auditory or visual stimulus if shock was administered immediately before the test session but not if shock occurred 5 or 25 min earlier (Experiment 1). Subjects pretreated with lithium chloride (LiCl) before a choice test between a novel saccharin solution and familiar tap water showed a reduced preference for saccharin if the LiCl was administered 35 min before testing but not if the LiCl was administered 6 hr earlier (Experiment 2). However, pretreatment with LiCl did not reduce subjects' preference for a novel visual or auditory stimulus, and footshock did not affect the preference for a novel saccharin solution (Experiment 3). This demonstration of selective sensitization effects is contrary to characterizations of sensitization as a general, nonspecific mechanism. The results are discussed in terms of anatomically mediated differential processing of interoceptive and exteroceptive stimuli.