Naloxone and shuttlebox self-stimulation in the rat

Rats self timed electrical brain stimulation on and off periods in a shuttlebox. Electrodes for self-stimulation were located either in the lateral hypothalamic area (LHA) or the periaqueductal gray (PAG). Doses of the narcotic antagonist, naloxone, were administered intraperitoneally immediately prior to self-stimulation testing. Doses of 1.0, 5.0, 10.0 or 50.0 mg/kg failed to alter shuttlebox self-stimulation behavior. These results are inconsistent with one lever-press self-stimulation study employing PAG electrodes [3], but agree with other studies using LHA electrodes [9, 15, 21, 24). Possible reasons for the discrepancy are suggested.