POSTSYNAPTIC 5-HT1A RECEPTORS MEDIATE 5-HYDROXYTRYPTAMINE RELEASE IN THE AMYGDALA THROUGH A FEEDBACK TO THE CAUDAL LINEAR RAPHE

Using brain microdialysis, it was demonstrated that the release of 5-h ydroxytryptamine (5-HT) in the central nucleus of the amygdala is unde r inhibitory control of somatodendritic and postsynaptic 5-HT1A recept ors. Systemic administration of flesinoxan, a selective 5-HT1A recepto r agonist, significantly reduced the extracellular levels of 5-HT in t he central nucleus of the amygdala. This effect could be completely an tagonized by the 5-HT1A receptor antagonist oxyphenyl)-1-piperazinyl)- N-(2-pyridyl)cyclohexane carboxamine trihydrochloride (WAY 100635). Lo cal administration of these compounds by reversed microdialysis into t he raphe nuclei revealed that extracellular 5-HT levels in the central nucleus of the amygdala can be regulated through 5-HT1A receptors in the caudal linear raphe nucleus, but not in the dorsal and median raph e nuclei. Interestingly, administration of flesinoxan into the central nucleus of the amygdala also decreased dialysate 5-HT levels both loc ally and in the caudal linear raphe nucleus. The former effect could b e blocked by pretreatment with WAY 100635 when applied into the centra l nucleus of the amygdala, but not when applied into the caudal linear raphe nucleus. These data provide circumstantial evidence for the exi stence of a 5-HT1A receptor mediated feedback loop from the central nu cleus of the amygdala to the caudal linear raphe nucleus. (C) 1997 Els evier Science B.V.