The effect of ascorbic acid on apomorphine-induced licking behavior in rat

Background and Purpose: Ascorbic acid an antioxidant vitamin is found throughout the mammalian central nervous system (CNS). There is evidence that it may modulate neuronal activity, release of neurotransmitters and dopamine receptors activities. There are behavioral evidences supporting the antidopaminergic effect of ascorbic acid. This effect of ascorbic acid may in part modulates the stereotyped behaviors-induced by dopaminergic system. The purpose of the present study was to determine the interaction between ascorbic acid and the stereotyped licking behavior in rat. Materials and Methods: In the present study, effects of ascorbic acid and different dopamine receptor antagonists on apomorphine-induced licking behavior were examined. For the induction of licking, the dose of 0.5 mg/kg, s.c. of apomorphine was used and the number of licking was recorded over a 75 min period. Results: Ascorbic acid (200-350 mg/kg, s.c.) dose-dependently reduced the licking behavior. Subcutaneous injection of ascorbic acid (250 mg/kg, ED61) potentates the inhibitory effect of dopamine D1 receptor antagonist, SCH 23390 (0.5 and 1 mg/kg, i.p.) but did not alter the inhibitory effect of dopamine D2 receptor antagonist, sulpiride (25 and 50 mg/kg, s.c.). Conclusion: These results suggest that the inhibitory effect of ascorbic acid on apomorphine-induced licking behavior is mediated by dopamine D2 receptor mechanisms.