To elucidate mechanism of action of nicotine in depression

Aims & Objectives: The present study was planned: • To study role of nicotine in depression by using serotonergic mechanism- Lithium induced head twitches. • To compare mechanism of action of nicotine given subcutaneously and by inhalation. Materials and Methods: Serotonergic mechanism of nicotine was studied in Lithium induced head twitches model in rats. 3 groups of 10 rats each were taken. Following drug treatments were administered: Control (vehicle) in a dose of 1 ml/kg administered subcutaneously, nicotine given subcutaneously (s.c.) (0.4 mg/kg) and inhalational route (0.2 mg/kg). Results: In this model, nicotine has shown serotonin induced behavioural changes producing ‘head twitches’ in rats using lithium. 1) In vehicle treated group, rats showed less number of head twitches. 2) In nicotine (s. c.) treated group, rats showed ‘lithium induced head twitches ’which started from 10 mins-90 mins. Result was highly significant compared with vehicle treated rats. 3) Inhalational administration of nicotine showed significant induction of head twitches at 10 mins -90 mins compared with vehicle treated rats. 4) When comparison of number of head twitches induced by nicotine (s. c.) with that of nicotine (inhalational) has shown that nicotine (s. c.) produced induction of head twitches for long lasting till 90 mins. While with that of nicotine (inhalational) produced short lasting action till 70 mins. Conclusion: 1) Serotonin mediated lithium induced head twitches was seen with both nicotine (s.c) and nicotine (inhalational) compared with that of vehicle treated group. 2) Nicotine administered by inhalational route showed short lasting action than nicotine administered subcutaneously.