Effects of benzodiazepine microinjection into the amygdala or periaqueductal gray on the expression of conditioned fear and hypoalgesia in rats.
Four experiments studied the effects of an intracranial microinjection of a benzodiazepine (midazolam) on the expression of conditioned fear (measured as passive avoidance) and conditioned hypoalgesia in rats. Unilateral microinjection of midazolam into the basolateral amygdala reduced both hypoalgesic and avoidance responses, whereas unilateral microinjection of midazolam into the ventrolateral region of the periaqueductal gray (vlPAG) reduced the hypoalgesic response but not the avoidance response. The results are discussed in terms of gamma-aminobutyric acid-ergic inhibition of antinociceptive mechanisms in the vlPAG and of the activation of these mechanisms by amygdala-based fear processes.
Harris
J A
JA
School of Psychology, University of New South Wales, Sydney, Australia.
Westbrook
R F
RF
D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001143:Arousal / Q000187:drug effects*; D001245:Association Learning / Q000187:drug effects; D001362:Avoidance Learning / Q000187:drug effects; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000187:drug effects*; D004292:Dominance, Cerebral / Q000187:drug effects; D005239:Fear / Q000187:drug effects*; D008297:Male; D011939:Mental Recall / Q000187:drug effects*; D008874:Midazolam / Q000494:pharmacology*; D009434:Neural Pathways / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects*; D010487:Periaqueductal Gray / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D011963:Receptors, GABA-A / Q000187:drug effects*; D012153:Retention, Psychology / Q000187:drug effects
D011963:Receptors, GABA-A; D008874:Midazolam