Role of cholinergic systems in pain modulation: I. Impact of scopolamine on environmentally induced hypoalgesia and pain reactivity.
Scopolamine was found to block both brief shock-induced (3 0.75-s, 1.0-mA shocks) and conditioned hypoalgesia on the tail-flick test in rats. The drug also produced a general increase in pain reactivity as measured by both the tail-flick test and shock-induced vocalization. It was shown that this hyperalgesia cannot account for the effect of the drug on brief-shock or conditioned hypoalgesia. Scopolamine did not block the nonopioid analgesia observed after long shock (3 25-s, 1.0-mA shocks). When the effect of the drug on baseline levels of pain reactivity was controlled, it potentiated long shock-induced hypoalgesia. Scopolamine also increased reactivity to tactile stimulation, which suggests the hyperalgesia reflects a general increase in arousal. None of these effects were observed with methylscopolamine, which suggests they are not peripherally mediated.
Grau
J W
JW
Department of Psychology, Texas A&M University, College Station 77843.
Illich
P A
PA
Chen
P S
PS
Meagher
M W
MW
D000818:Animals; D001143:Arousal / Q000187:drug effects*; D004597:Electroshock; D006185:Habituation, Psychophysiologic / Q000187:drug effects; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D019832:N-Methylscopolamine; D009619:Nociceptors / Q000187:drug effects*; D010276:Parasympatholytics; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D011950:Receptors, Cholinergic / Q000187:drug effects*; D012601:Scopolamine / Q000494:pharmacology*; D012602:Scopolamine Derivatives / Q000494:pharmacology; D012684:Sensory Thresholds / Q000187:drug effects; D012931:Social Environment; D014828:Vocalization, Animal / Q000187:drug effects
D010276:Parasympatholytics; D011950:Receptors, Cholinergic; D012602:Scopolamine Derivatives; D012601:Scopolamine; D019832:N-Methylscopolamine