Capsazocaine: A capsaicin-sensitive functional antagonist displays an argument on sensory capsaicin receptor

Abstract

1. 1. Intravenous infusion of capsazocaine (CAPBZ), a molecular fusion product of irritant synthetic capsaicin and local analgesic benzocaine, at 100 μg/kg/min for 15 min inhibited capsaicin (10 μg/kg, IV)-induced spinal release of substance P-like immunoreactivity and vagus reflex responses in blood pressure and heart rate changes in rats. 2. 2. Intrathecal perfusion of CAPBZ (1.0 nM) also reversed retrograde epigastric intraarterial capsaicin (10 μg/kg)-induced hypotensive spinal reflex. 3. 3. In isolated guinea pig tissues, CAPBZ (1.0–100.0 μM) inhibited capsaicin (1.0 nM)-sensitive sensory and functional activities, including cardiatonic, bronchial, tracheal and ileal contractilities. CAPBZ is suggested to be a capsaicin antagonist.