LESIONS IN THE MEDIAL FOREBRAIN BUNDLE: DELAYED EFFECTS ON SENSITIVITY TO ELECTRIC SHOCK.

Rats with bilateral lesions in the medial forebrain bundle demonstrate both an increased sensitivity to electric shock, as reflected by a lowered jump threshold, and a decrease in the concentration of serotonin in the brain. Both effects of the lesion are characterized by a delayed time of onset and gradual development, which approximates the time required for progressive nerve degeneration in the central nervous system. It is suggested that this behavioral effect of bilateral lesions in the medial forebrain bundle may be due to a central denervation supersensitivity.