Functional properties of neurons in cat trigeminal subnucleus caudalis (medullary dorsal horn). II. Modulation of responses to noxious and nonnoxious stimuli by periaqueductal gray, nucleus raphe magnus, cerebral cortex, and afferent influences, and effect of nalaxone - Sessle,B.J.; Hu,J.W.; Dubner,R.; Lucier,G.E. (J Neurophysiol, 1981)