Modulation of nicotine-induced analgesia by calcium agonist and antagonist in adult rats.

The involvement of calcium in nicotine-induced analgesia in male rats was explored using the tail-flick test. A single dose of nicotine (1 mg/kg SC) produced a maximal effect on tail-flick latency (15 s) within 8-10 min, which lasted for 4 min. Pretreatment with the calcium chelator, EDTA (250 microM/kg SC four injections at 15 min intervals), before the single dose of nicotine accelerated the onset and prolonged the duration of the nicotine-induced analgesia. The maximal effect on tail-flick latency occurred within 2 min and lasted for 10-20 min. Conversely, pretreatment with calcium chloride (1.5 mM/kg IP) attenuated nicotine-induced analgesia. It is suggested that nicotine may exert its antinociceptive effects via modulation of calcium fluxes across the neural membrane.