ALTERED SENSITIVITY TO FOOTSHOCK AND DECREASED BRAIN CONTENT OF SEROTONIN FOLLOWING BRAIN LESIONS IN RAT

273 Holtzman Sprague-Dawley rats with lesions in the ventrolateral tegmentum which ablated 50% of the medial lemniscus, the presumed primary projection system for pain, demonstrated a decreased sensitivity to electric shock as measured by an 84% elevation of the mean jump threshold. Lesions in the medial forebrain bundle, septal area, or dorsomedial tegmentum increased sensitivity to electric shock and decreased brain concentrations of serotonin. The septal area and dorsomedial tegmentum are strongly interconnected via the medial forebrain bundle by both ascending and descending fibers. It is concluded that lesions in this anatomical system increased sensitivity to electric shock by virtue of their effects on telencephalic serotonin. Serotonin normally functions to inhibit effects of a painful stimulus. (25 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.