Unilateral lesion of the intrinsic cells in the medial forebrain bundle depresses self-stimulation but not stimulus-bound locomotor activity

Abstract

The intrinsic neurons of the medial forebrain bundle were unilaterally destroyed, in rats, through local injection of ibotenic acid (4 micrograms in 0.5 microliter). Ten days later, electrodes were bilaterally implanted, one in the lesioned lateral hypothalamus, the other into the contralateral hypothalamus. Firstly, self-stimulation was studied with stimulation of each electrode separately. Later on, the effect of non-contingent electrical stimulation on evoked locomotor activity in the open-field was analysed for each electrode. While self-stimulation of the lesion area was greatly depressed in comparison with the unlesioned lateral hypothalamus, the increase in locomotor activity produced by stimulation, at the intensity applied, was the same whether the stimulated hypothalamus was lesioned or not.