AUDITORY-EVOKED POTENTIALS AS INDICATOR OF BRAIN SEROTONERGIC ACTIVITY - FIRST EVIDENCE IN BEHAVING CATS

Due to the increasing importance of the central serotonergic neurotran smission for pathogenetic concepts and as a target of pharmacotherapeu tic interventions in psychiatry, reliable indicators of this system ar e needed Several findings from basic and clinical research suggest tha t the stimulus intensity dependence of auditory evoked potentials (AEP ) may be such an indicator of behaviorally relevant aspects of seroton ergic activity (Hegerl and Juckel 1993, Biol Psychiatry 33:173-187.). In order to study this relationship more directly, epidural recordings over the primary and secondary auditory cortex were conducted in chro nically implanted cats under intravenous (i.v.) administration of drug s influencing the serotonergic and other modulatory systems (8-OH-DPAT , m-CPP, ketanserin, DOI, apomorphine, atropine, clonidine). The inten sity dependence of the cat AEP component with the highest functional s imilarity to this of the N1/P2-component in humans was significantly c hanged by influencing 5-HT1a, and 5-HT2 receptors, but not 5-HT1c rece ptors. This serotonergic modulation of the intensity dependence was on ly found for the primary auditory cortex which corresponds to the know n different innervation of the primary and secondary auditory cortex b y serotonergic fibers. Our study supports the idea that the intensity dependence of AEP could be a valuable indicator of brain serotonergic activity; however, this indicator seems to be of relative specificity because at least cholinergic effects on the intensity dependence were also observed. (C) 1997 Society of Biological Psychiatry.