Effects of ibotenic acid lesion in the basal forebrain on electrical self-stimulation in the middle part of the lateral hypothalamus.

The aim of the present study was to analyse the involvement of neurons located in some basal forebrain areas in electrical self-stimulation elicited from the middle part of the lateral hypothalamus. The anterior hypothalamic region was unilaterally lesioned by local injection of ibotenic acid. Ten to 20 days later 4 electrodes were implanted bilaterally, two at the lesion level and two in the middle lateral hypothalamus. A small but significant self-stimulation deficit was observed in the lesioned area, while self-stimulation on the contralateral side was normal. At the middle lateral hypothalamic level, no deficit was observed when stimulation was applied either ipsilaterally or contralaterally to the anterior lesioned side. In most cases the lesion destroyed the dorsolateral part of the lateral preoptic area, the ventral pallidum-substantia innominata complex and the lateral part of the bed nucleus of the stria terminalis. Given the fact that these regions are known to project massively to the middle lateral hypothalamic area, our data suggest that descending influences originating in the damaged regions are not involved in self-stimulation elicited from the middle hypothalamus.