Potentiation of stress-induced analgesia (SIA) by thiorphan and its block by naloxone.
Exposure of rats to inescapable footshock produces an analgesic effect. To determine if endogenously released enkephalins play a role in this phenomenom, rats were treated with the enkephalinase inhibitor thiorphan (T), exposed to inescapable stress, and tested in the tail-flick test for antinociception. T (10-100 mg/kg sc) caused a dose-related potentiation of both the peak effect and the duration of the SIA. This effect was blocked by doses of naloxone (1 mg/kg sc) that did not affect baseline response latencies.
D000603:Amino Acids, Sulfur / Q000494:pharmacology*; D000818:Animals; D004745:Enkephalins / Q000502:physiology; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010146:Pain; D011480:Protease Inhibitors / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological; D015244:Thiorphan; D008625:Tiopronin / Q000031:analogs & derivatives / Q000494:pharmacology*
D000603:Amino Acids, Sulfur; D004745:Enkephalins; D011480:Protease Inhibitors; D009270:Naloxone; D015244:Thiorphan; D008625:Tiopronin