Baumeister A A, Anticich T G, Hawkins M F, Liter J C, Thibodeaux H F, Guillory E C
Department of Psychology, Louisiana State University, Baton Rouge 70803.
Brain Res. 1988 Apr 26;447(1):116-21. doi: 10.1016/0006-8993(88)90971-7.
The present study sought to determine whether opiate receptors in the substantia nigra may mediate antinociception produced by systemic morphine. Bilateral intranigral microinjection of naloxone-HCl (0.3-10 micrograms) suppressed the antinociceptive effects of systemically administered morphine sulfate (5 mg/kg, s.c.) on the tail-flick and hot-plate tests in a dose-related manner. Injection of naloxone (3 micrograms) into the ventral tegmental area did not alter antinociception produced by systemic morphine (5 mg/kg, s.c.). These findings support the argument that the substantia nigra is an essential, and previously unrecognized, component of the endogenous pain suppression system.
