The effects of serotonergic compounds on evoked responses in the dentate gyrus and CA1 region of the hippocampal formation of the rat.

The effects of serotonin (5-HT), the 5-HT1A receptor subtype agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and the 5-HT2 receptor subtype agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) on electrophysiological responses in the dentate gyrus and area CA1 were examined in the in vitro hippocampal slice preparation. Superfusion of either serotonin or 8-OH-DPAT in the bath was found to inhibit population responses in a dose-dependent manner in both regions, with a greater effect in the CA1. The effects of 8-OH-DPAT in both regions were attenuated significantly by the serotonergic antagonist methysergide, as were the effects of 5-HT on the population spike in the CA1. The application of DOI did not produce statistically significant effects in either region. These findings support an inhibitory role for the 5-HT1A receptor in both area CA1 and the dentate gyrus.