INHIBITORY MODULATION OF LONG-TERM POTENTIATION VIA THE 5-HT(1A) RECEPTOR IN SLICES OF THE RAT HIPPOCAMPAL DENTATE GYRUS

Modulation of long-term potentiation (LTP) and isoproterenol-induced long-lasting potentiation (ILLP) via the 5-HT1A receptor was examined in slice preparations of the rat hippocampal dentate gyrus. 8-OH-DPAT, a selective agonist of the 5-HT1A receptor, decreased population spike (PS) amplitude in these preparations, in a dose-dependent manner. Application of NAN-190, an antagonist of the 5-HT1A receptor, blocked the 8-OH-DPAT-induced decrease in PS amplitude. LTP was not affected by application of 8-OH-DPAT during tetanic stimulation (TS), while in contrast, application of NAN-190 during TS significantly augmented LTP. The NAN-190-induced enhancement of LTP was reversed by 8-OH-DPAT. In addition, a dose-dependent inhibition of isoproterenol-induced long-lasting potentiation was produced by simultaneous application of 8-OH-DPAT and isoproterenol. These results suggests that 5-HT modulates LTP in the hippocampal dentate gyrus via the 5-HT1A receptor, in an inhibitory fashion.