8-OH-DPAT impairs spatial but not visual learning in a water maze by stimulating 5-HT1A receptors in the hippocampus

The effect of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), a 5-HT_1A receptor agonist, on spatial and non-spatial learning in a water maze was studied using two tasks of equal difficulty, with the same motor, motivational and reinforcement demands. Rats were examined for choice accuracy in a two-platform spatial discrimination task. Rats treated subcutaneously with 100 μg/kg 8-OH-DPAT were impaired in choice accuracy with no effect on latency. Treated rats made more errors of omission than controls only on days 1 and 2 of training. Infusion of 1 μg/μl spiroxatrine (SPX) or 5 μg/μl of (+) WAY100135, two potent 5-HT_1A receptor antagonists, in the CA1 region of the dorsal hippocampus antagonized the impairment in choice accuracy caused by 8-OH-DPAT. The effect on errors of omission on days 1 and 2 of training were not significantly modified by spiroxatrine or (+) WAY100135. Rats treated with 8-OH-DPAT were not impaired in their ability to learn a visual discrimination in a water maze. The results suggest that stimulation of 5-HT_1A receptors in the CA1 region of the dorsal hippocampus impairs spatial but not visual discrimination in rats.