Responses of neurons of the nucleus raphe magnus to noxious stimuli.

Extra-cellular recordings were made from neurons located in nuclei raphé magnus (nRM) and reticularis paragigantocellularis (nRPGC) of intact rats. Noxious cutaneous and visceral stimuli elicited either excitatory or inhibitory effects, unaffected by innocuous stimuli while most of the noxious-inhibited neurons gave brief excitatory responses to innocuous brisk taps. It is suggested that the organization of these areas and their involvement in analgesic effects is much more complex than previously described.