Light pentobarbital anesthesia diminishes the antinociceptive potency of morphine administered intracranially but not intrathecally in the rat.
The antinociceptive activity of morphine administered intracerebrally in the periaqueductal gray or intrathecally was compared in adult male rats in the awake and lightly pentobarbital-anesthetized states. The potency of morphine administered intrathecally was the same in both the awake and lightly anesthetized states. In contrast, the antinociceptive potency of morphine administered intracerebrally was attenuated significantly in the lightly anesthetized state. It is suggested that pentobarbital depresses the descending inhibitory pathway(s) activated by morphine administered in the periaqueductal gray.
D000758:Anesthesia; D000818:Animals; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D009619:Nociceptors / Q000187:drug effects*; D010424:Pentobarbital; D010487:Periaqueductal Gray / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D009020:Morphine; D010424:Pentobarbital