Pain suppression induced by electrical stimulation of the pontine parabrachial region. Experimental study in cats.

Cholinergic stimulation by microinjection of drugs into a region surrounding the lateral half of the brachium conjunctivum selectively produces a non-opiate form of pain suppression in the cat. Since this suppression does not appear to involve neural systems that mediate morphine analgesia, stimulation of this pontine parabrachial region (PBR) may potentially be useful for control of human pain resistant or tolerant to opiate treatment. Because of technical problems associated with the clinical use of microinjection techniques in the human brain, we investigated whether electrical stimulation of the PBR can produce pain suppression similar to pain suppression produced by cholinergic stimulation. The results indicate that electrical stimulation of an area generally corresponding to the PBR can also produce significant pain suppression. Although the PBR is a region previously implicated in a variety of behavioral and physiological functions, the stimulation parameters that produce maximal pain suppressive effects (namely, low frequency and relatively low intensity) were not associated with noticeable changes in such functions. The prolonged onset period and persistent analgesic effects outlasting the period of stimulation--features that have been reported in other studies of brain stimulation-produced pain suppression--were observed in the present study. The time course of pain suppression did not parallel other changes in behavioral and physiological functions. These data indicate that electrical stimulation of the PBR, under certain stimulation parameters, can activate previously demonstrated neural populations related to pain suppression without affecting neural elements contributing to other behavioral or physiological functions. The authors suggest that electrical stimulation of the PBR may be clinically applicable for treatment of human pain.