The effect of an intraperitoneal injection of capsaicin on the thermopreferendum in the frog (Rana esculenta).
In 7 frogs (Rana esculenta) weighing 70 to 180 g, thermopreferendum (Thp), measured by recording cutaneous temperature (Ts) in the animal placed in the warm end of an aqueous temperature gradient (0 degree C-40 degrees C), equalled 25 +/- 2 degrees C. After an intraperitoneal (IP) injection of 20 mg/kg of capsaicin, Thp was significantly decreased and equalled 3 +/- 1 degree C. The frogs then remained in the cold end of the gradient for 60 minutes. When the time of observation was extended to 3 hours, one frog died from hypothermia. Seven to 24 days after the capsaicin injection, Thp was still decreased in 4 surviving frogs (Thp = 15 +/- 2 degrees C). Capsaicin or isotonic saline solution injected in frogs maintained at 25 degrees C ambient temperature had no effect on Ts or on cloacal temperature. According to results previously obtained in homeothermic species, small doses of capsaicin activated heat-loss responses in the frog.
D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D011893:Rana esculenta; D012881:Skin Temperature / Q000187:drug effects
D002211:Capsaicin