In monkeys trained to detect and discriminate noxious heat stimuli, morphine microinjected into the medullary dorsal horn attenuated the perceived intensity of noxious heat in a dose- and stimulus-dependent fashion. These data demonstrate a pharmacologically specific effect of opiates on the sensory intensity component of pain at the earliest central relay pathway transmitting noxious information. © 1986.
Oliveras, J. L., Maixner, W., Dubner, R., Bushnell, M. C., Duncan, G., Thomas, D. A., & Bates, R. (1986). Dorsal horn opiate administration attenuates the perceived intensity of noxious heat stimulation in behaving monkey. Brain Research, 371(2), 368–371. https://doi.org/10.1016/0006-8993(86)90377-X