The capsaicin test in mice for evaluating tachykinin antagonists in the spinal cord.
A capsaicin test involving peripheral nociception, which produces behaviour similar to that elicited by formalin, is described in mice. Capsaicin was injected subcutaneously (s.c.) into the dorsal surface of a hindpaw and the time the animals spent licking the paw was recorded. Doses of capsaicin of 6.25-1600 ng induced nociception, during a period of 5 min, starting immediately after injection and disappearing completely at 10 min. Intrathecally (i.t.) administered [D-Arg1,D-Trp7,9,Leu11]substance P (spantide), a tachykinin antagonist and [D-Phe7,D-His9]substance P (6-11), a selective antagonist of substance P (SP), inhibited the capsaicin-induced behaviour, in a dose-dependent manner. This licking behaviour was also inhibited by intrathecal administration of SP antiserum but not by somatostatin (SOM) antiserum. Intrathecal pretreatment with capsaicin resulted in a marked reduction of the licking response, following subcutaneous injection of capsaicin into the paw. Capsaicin-induced licking was not affected by intrathecal administration of cyclo[7-aminoheptanoyl-Phe-D-Trp-Lys-(OBz)-Thr], a SOM antagonist and by intrathecal pretreatment with cysteamine, a SOM depletor. This nociceptive test may allow discrimination between SP- and SOM-mediated responses in the spinal cord of the mouse.
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002211:Capsaicin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007278:Injections, Spinal; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D010147:Pain Measurement; D013116:Spinal Cord / Q000187:drug effects*; D013373:Substance P / Q000031:analogs & derivatives / Q000494:pharmacology; D015320:Tachykinins / Q000037:antagonists & inhibitors*
D000700:Analgesics; D015320:Tachykinins; D013373:Substance P; C042867:spantide; D002211:Capsaicin