A COMPARISON OF DIFFERENT SENSORY STIMULI IN PRODUCING CONDITIONED APOMORPHINE EFFECTS

In previous studies, it was shown that apomorphine-induced stereotyped behaviour could be conditioned when apomorphine was repeatedly paired with sensory stimuli (CS). Since in these experiments, the sum of var ious sensory stimuli were applied, it seemed of interest to use each s ensory stimulus separately in order to evaluate the relevance of each of the stimuli for the development of the conditioned responses (CRs). Therefore, apomorphine (0.5 mg/kg s.c.) was repeatedly (six times) pa ired either with an auditory, an olfactory, a tactile or a compound (a uditory + olfactory + tactile) stimulus. On the seventh (drug-free tes t) day, the rats were injected with solvent in the presence of the CS previously applied. It was shown that the olfactory stimulus alone whe n used as CS produced similar CRs (in particular, stereotyped sniffing and licking) as the compound stimulus, whereas the other stimuli appl ied did not noticeably contribute to the development of the CRs. Furth ermore, similarly to the compound stimulus, the olfactory stimulus, bu t not the auditory or tactile one, enhanced the apomorphine-induced st ereotypies in the presence of the CS. This result suggests that the ap plication of olfactory stimuli might be of particular relevance for th e development of conditioned dopaminergic responses.