Regional Effects of Hypothalamic Lesions on Brain Serotonin

THE BIOGENIC amine, serotonin, is distributed widely throughout the central nervous system but occurs in highest concentration in a core of tissue extending from limbic areas of the telencephalon and caudate nucleus through the hypothalamus and central brainstem.1-3The functional role of serotonin in brain is unknown and, until recently, no association of this amine with a specific anatomic system had been established except for the gross tissue localizations noted above. Evidence for such an association was provided by the finding that bilateral destruction of the medial forebrain bundle or ablation of areas known to contribute fibers to that tract in the lateral hypothalamus causes a significant decrease in total brain serotonin in the rat.4Unilateral lesions produce a similar effect on brain serotonin but one which is confined to the longitudinal brain half in which the tract was transected.5This finding is in accord with