Paradoxical effects after microinjection of morphine in the periaqueductal gray matter in the rat

192 (to iraagine pleasant events or io lm~.gine the finger as insensitiv,,~) showed a reduction in pain as compared to uninstructed control subjects. Subjects -:ed to expect a reduction in pain, but not provided with cognitive strategies, also ~howed reduced pain ,:luring the post-test as compared to control subjects, but the reduc~tion ~vassmaller than for subjects using cognitive strategies. An experimenter modeling procedure, used with one-half of the subjects under each experimental treatrrent, was effective in reducing verbal reports of pain only for subject.,: with high pr-,'test levels who were asked to imagine pleasant events.

PSYCHOLOGY

Paradoxical effects after microinjection of morphine in th~ l)eriaqueductal gray matter in the rat '(. F. Jacquet and A. Lajtha, Science, 185 (1974) 1055-1057 Paradoxical. concurrent hyper- and hyporeactivity of a profound nature to specific stimuli occm red when 16,ug of morphine was microinjected bilaterally into the periaqueductal gray matter of the rat brain. Bo,:h effects at this site were dose-dependent. The hyperreactivity (to previously neutral auditory and visual stimuli) was obtained only with intracerebrally injected morphine and never with intraperi,oneally injected morphine or with other opiates admir istered either way. Rapid tolerance to toxic doses of morphine developed at this site, as well as cross tolerance of the hyporeactivity to painful stimuli between routes (intracerebral to intraperitoneal) of morphine administration. Both the hyper- and hyporeactivity were fully reversible by intracerebral injection of naioxone in the periaqueductal gray. Thus, the periaqueductal gray appears to be a major pathway for morphine action.

A neodissociation interpretation of pain r(.,duction in hypnosis E. R. Hilgard, Psychol. Rev., 80 (1973) 396-411 When cold pressor pain is reduced through hypnotically suggested analgesia, the concomitant changes in heart rate and blood pressure remain essentially what they were when the pain of the ice water was normally perceived. Investigation of this somewhat paradoxica! finding by way of hypnotically induced automatic writing (or its equivalent in aulomatic keypressing or automatic talking) reveals that at some cognitive level the subject has experienced the cold and can report its intensity, even though the saffering may be reduced. The theoretical problems posed by the experiment are presented according to a possible neodissociation interpretation, compared