Localization of the Antinociceptive Action of Morphine in Primate Brain.
Technical rept. Dec 73-Dec 74,
EDGEWOOD ARSENAL ABERDEEN PROVING GROUND MD
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Microinjections of morphine sulfate 20 to 40 micrograms were made into various subcortical regions of the rhesus monkey brain. The effects of these injections were evaluated on the nociceptive threshold, as defined by the shock titration technique. The results of this preliminary investigation indicate that the region of maximal antinociceptive sensitivity to morphine in the primate is the periventricular-periaqueductal gray matter. It is tentatively suggested that morphine lowers the affective tone or the aversive component of pain by its action on the midbrain central gray and periventricular areas - both important projection and integration areas of the extralemniscal somatosensory system. Author