Effects of damage to median raphe nucleus on ingestive behavior and wheel running activity.

The effects of damage to the median raphe nucleus on the ingestive behavior and wheel running activity of rats were studied. This nucleus was damaged by the placement of either electrolytic or chemical (5,7-dihydroxytryptamine) lesions. After the placement of either type of lesion, wheel running activity was significantly decreased for the duration of the 8 week post-operative period. Although there were transient decreases in both food and water intakes after damage to the median raphe nucleus, these decreases did not appear to result from impairments in neuro-regulatory mechanisms. Rather, the decrease in food intake seemed to be related to the decrease in locomotor activity, and the decrease in water intake appeared to be linked to the decrease in food intake. In some rats with electrolytic lesions in the median raphe nucleus, the decrease in water intake was followed by a transient period of hyperdipsia.