Eegraphic and behavioural effects of ondansetron, a 5HT3 antagonist, in rabbits

1. EEGraphic and behavioural effects of ondansetron, a 5HT3 antagonist, have been studied in the rabbit. Subsequently we tested the neurophysiological and behavioural interactions between ondansetron and L-5-HTP induced serotonergic syndrome. 2. The drug produced a dose-dependent (0.001, 0.01, 0.1 mg/kg i.v.) increase in the cortical power density spectrum, particularly in the range of the lowest frequencies bands. This effect is expression of cortical synchronization. 3. The lowest and mild dose, but not the highest, failed to produce behavioural sedation and to inhibit the arousal induced by vibroacustical stimulation. 4. L-5-HTP (10 mg/kg i.v.) administration generated a typical EEGraphic-behavioural pattern characterized by a decrease of cortical power spectrum density and stereotyped movements. The EEGraphic effects were significantly suppressed by administration of mild and higher doses of ondansetron, while the behavioural effects were inhibited by all doses tested. 5. It is concluded that ondansetron acts with considerably efficacy on central nervous system. The administration of low and mild doses shows a singular dissociation between EEGraphic and behavioural actions. The inhibition of the L-5-HTP behavioural syndrome by ondansetron suggests that this drug acts on behaviour only when there is an altered physiological pattern.