Locomotor activity and ingestive behavior after damage to ascending serotonergic systems

The effects of electrolytic midbrain raphe lesions on ingestive behavior and locomotor activity of rats were compared to those produced by intracerebral injections of 5,7 dihydroxytryptamine (5,7 DHT) at various points along the ascending serotonergic pathways. Only electrolytic lesions of the median and/or dorsal raphe nuclei produced significant changes in food intake, water intake, body weight gain, and wheel running activity. Intracerebral injections of 5,7 DHT, a selective serotonergic neurotoxin, had no effect on any of these variables. However, 5,7 DHT induced lesions produced decreases in forebrain synaptosomal uptake of serotonin which were equivalent to, or greater than, those resulting from electrolytic lesions of the midbrain raphe nuclei. Failure of 5,7 DHT injections to replicate the behavioral changes resulting from electrolytic lesions of the midbrain raphe nuclei suggests that loss of ascending serotonergic projections was not responsible for the behavioral effects that followed the electrolytic lesions.