ACTIONS OF NIMODIPINE ON THE SEROTONERGIC SYSTEMS OF RAT-BRAIN

1. The effects of the serotonin (5-HT) precursor, L-5-hydroxytryptopha n (L-5-HTP), or the selective 5-HT1A receptor agonist, 8-OHDPAT, on be havior or brain 5-HT metabolism or both were evaluated in rats IP pret reated with nimodipine at doses ranging from 0.31 to 40 mg/kg. 2. Nimo dipine, in a wide dose range (0.6-20.0 mg/kg) potentiated the head-twi tch response to L-5-HTP. 3. The effects of nimodipine on the 5-HT meta bolism of rats treated with L-5-HTP did not comply with the increase i n the behavioral response to this 5-HT precursor. 4. Nimodipine antago nized the effects on 5-HT metabolism induced by 8-hydroxy-2-(di-N-prop yl-amino)-tetralin through stimulation of 5-HT1A autoreceptors. 5. It was concluded that the effects of nimodipine on brain 5 HT metabolism appeared to be linked to activation of serotonergic neurotransmission likely due to inhibition of the back regulation mechanism mediated by presynaptic 5 HT1A receptors. (C) 1997 Elsevier Science Inc.