Effects of the vanilloid agonist olvanil and antagonist capsazepine on rat behaviors.

Vanilloid receptors (VR) are molecular integrators of painful chemical and physical stimuli. Olvanil is an agonist of the vanilloid receptor; capsazepine is a competitive VR antagonist. The authors were interested in investigated the effects of these compounds on anxiety-like behaviors in rats using the elevated plus maze. In addition, the authors examined the effects of olvanil on the Porsolt swim test. Doses of 0, 0.2, 1.0 and 5.0 mg/kg olvanil, respectively, yielded percent open arm entries at 5 min of 25+/-10.1, 19.3+/-7.1, 14.9+/-5.9 and 0+/-0. We demonstrated a drug effect by showing that the mean of the 0.2, 1 and 5 mg/kg doses was significantly lower than the 0 mg/kg dose at P<.05. In addition, the authors examined the effect of olvanil on the ability of rats to perform in the Porsolt swim test. Float time for rats was tested with 0.1 or 2 mg/kg olvanil and differences between the float times for the lower and higher doses were significant at P<.05. In addition, the effects of various doses of the vanilloid antagonist capsazepine was examined on elevated plus maze behavior. Doses of 0, 1, 5 and 10 mg/kg yielded percent time in the open arms at 5 min of 1.46+/-1.38, 15.05+/-10.42, 11.54+/-10.57, and 14.56+/-7.86. The mean of the 1, 5 and 10 mg/kg doses was significantly greater than the percent time in the open arms for the vehicle, consistent with a drug effect. The results suggest that the vanilloid agonists and antagonists may impact on behaviors involving anxiety and affect. However, it cannot be ruled that the findings could be due to nonspecific motor effect.