Electrical self-stimulation of dentate gyrus granule cells.

Male albino rats implanted with a chronic stimulating electrode electrophysiologically guided into the granule cell layer of the dorsal dentate gyrus were tested in a self-stimulation paradigm. It was found that subjects self-administer electrical stimulation to the granule cells at low, steady rates. Consistent with the presence of opioid-like immunoreactivity in the granule cell mossy fiber pathway, intraperitoneal injection of the opiate antagonist naloxone diminishes granule cell self-stimulation in a dose-related fashion. The results suggest that a granule cell opioid synapse participates in expression of reward at this site.