The effect of ascorbic acid on I.V. self administration of morphine in rats

Background: Ascorbic acid which is an antioxidant vitamin, released from brain glutaminergic neurons and regulates the synaptic action of dopamine and glutamate. Dopaminergic and glutaminergic systems involve in tolerance and dependence on morphine and in morphine withdrawal syndrome. Objective: In this study the effect of Ascorbic acid on self administration of morphine in rats has been investigated. Methods: Male rats (250-300 gr) were anaesthetized and implanted with silastic catheters inserted into the right jugular vein. After 5 days the animals were fitted and the external end of the catheter was connected to a syringe-driven pump, then were placed in the self administration apparatus that had two lever (active, passive) for 2 hours every day. Active lever switched on the infusion pump for 10sec, injecting 1ml of saline or saline containing 5 mg/ml of morphine (training period was 10days). In one group of rats (n=6), ascorbic acid (500mg/kg.IP) were injected and its effects on auto-infusion of morphine were assessed. Findings: Injection of ascorbate (500 mg/kg. IP) prevents the development of tolerance and dependence on morphine in rats. Conclusion: Ascorbate can antagonized the reinforcing effect of morphine and can be used as an effective pharmacotherapy for morphine abuse specially when used with high dose.