Adrenergic Component of Nicotine Antinociception in Rats

It has been widely established that nicotine , the active pharmacological agent in tobacco has antinociceptive effects , but the mechanism of this activity is yet to be fully investigated . The present study examined the effects of two adrenergic receptor antagonists , propranolol and prazosin .on nicotine antinociception using the hot plate (HP) paradigm in adult male Wister rats ( 180-220gm ) . Three groups of rats received respectively , first , saline ( 10ml/kg) intraperitoneally ( ip) plus intravenous ( iv) nicotine (1ml/kg ) , second , propranolol ( 10-30mg/kg, ip ) plus nicotine and the last group had prazosin (0.2- 1.0mg/kg , ip ) followed by the same dose of nicotine .Nociception was measured at 15 mins intervals for one hour . While the administration of normal saline had no effect on the supraspinally mediated hot plate latencies , both propranolol and prazosin reduced the hot plate responses ( significant at 15 , 30 ,45 and 60 mins , post injection) .These findings suggest the involvement of the adrenergic system in nicotine induced antinociception.