DOPAMINERGIC AND SEROTONERGIC NEUROTRANSMISSION SYSTEMS ARE DIFFERENTIALLY INVOLVED IN AUDITORY-CORTEX LEARNING - A LONG-TERM MICRODIALYSISSTUDY OF METABOLITES

Auditory cortex has been shown to be a site of widespread neuronal lea rning processes even in the context of simple auditory conditioning be havior. In view of their presumed role in determining behavioral and m otivational relevance of incoming information we investigated whether the dopaminergic and serotonergic systems are involved in auditory cor tex learning. Using a chronic brain microdialysis technique over 4 day s, samples from auditory cortex were obtained before, during, and afte r daily footshock avoidance training simultaneously from trained gerbi ls and passive control animals or pseudotrained animals. Because of de tection limits of dopamine and serotonin in auditory cortex, the respo nse profiles of extracellular homovanillic acid as the metabolite of t he dopaminergic system and of 5-hydroxyindoleacetic acid as the metabo lite of the serotonergic system were determined from consecutive dialy sis samples each day. The response of the dopaminergic system appeared to reflect the initial formation of the behaviorally relevant associa tion exclusively during the first training day, whereas the serotonerg ic response appeared to correlate with the stress level of animals.