Electrolytic raphe magnus lesions block analgesia induced by a stress-morphine interaction but not analgesia induced by morphine alone.
Morphine analgesia in the tail withdrawal test was examined in rats which had had lesions of the nucleus raphe magnus (NRM) or sham operations. Half of the rats were tested while restrained, whereas the other half were not restrained. In the sham-operated rats, restraint potentiated the analgesic response to morphine. Lesions of the NRM had no effect on unrestrained rats but reduced the morphine analgesia exhibited by restrained rats so that it was indistinguishable from that of unrestrained rats. The NRM seems to be involved in analgesia induced by an interaction of morphine and restraint but not in analgesia induced by morphine alone.
D000818:Animals; D001931:Brain Mapping; D006801:Humans; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010146:Pain / Q000150:complications / Q000503:physiopathology*; D011903:Raphe Nuclei / Q000503:physiopathology*; D051381:Rats; D012149:Restraint, Physical; D012701:Serotonin / Q000502:physiology; D013315:Stress, Psychological / Q000150:complications / Q000503:physiopathology*
D012701:Serotonin; D009020:Morphine