Instillation of 50 μL capsaicin solution (10 μg/mL) into the left eye of the rat evokes 12.9±1.3 wiping movements within 3 min. Pretreating the rats with 0.4 or 1 mg/kg i.p. JYL 1421 does not influence significantly the wiping behavior, but 2-5 mg/kg dose-dependently reduces the number of wiping movements. The ID50 value is 4.6 mg/kg. The mean arterial pressure of untreated rats is 109.9±4.2 Hgmm (n=6). One and 2 μg/kg capsaicin i.v. injection evokes a transient drop of blood pressure by 47.4±4.7 and 59.6±4.2 Hgmm (n=6), respectively. Both applied doses of JYL 1421 (0.4 and 1.6 mg/kg) fail to evoke hypotension. JYL 1421 dose-dependently inhibits the capsaicin-induced fall in blood pressure as shown by the need for higher capsaicin doses to elicit the reflex hypotension after JYL 1421 administration than before treatment. Capsazepine fails to induce a significant inhibition of the capsaicin-evoked hypotension up to a dose of 2 mg/kg[1].
