Modulation of the vestibulo-ocular reflex by serotonin in the rat.
The effects of intraventricular injection of serotonin (5-HT) and its agonists and antagonists on the amplitude of the vestibulo-ocular reflex were studied in chronic implanted rats. 5-HT (10(-5) M) triggers an increase of the amplitude of the reflex which lasts 30 min. Similar results are obtained when N,N-dimethyl-5-methoxytryptamine (10(-3) M) is introduced into the ventricular cannula. The increasing effects observed both with 5-HT and N,N-dimethyl-5-methoxy-tryptamine are abolished by methiothepin, a potent antagonist of 5-HT receptors. Injection of indirect agonists like pargyline, a monoamine oxidase inhibitor, or fluoxetine, a potent inhibitor of 5-HT reuptake, is followed by an increase of the amplitude of the vestibulo-ocular reflex. These results indicate that 5-HT can modulate the activity of the vestibulo-ocular pathway and muscular tone of extraocular muscles. Location and involvement of various modulating 5-HT sites are discussed.
D000818:Animals; D004558:Electric Stimulation; D007276:Injections, Intraventricular; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D008732:Methoxydimethyltryptamines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012027:Reflex, Vestibulo-Ocular / Q000187:drug effects*; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*
D008732:Methoxydimethyltryptamines; D012701:Serotonin; D008719:Methiothepin