Thunbergia laurifolia linn. Extract protects ethanol addiction and increases dopamine synthesis

Abstract

Thunbergia laurifolia Linn. is a plant used in traditional medicine for the detoxification of several substances including ethanol. Previous studies showed that T. laurifolia increased neuronal activity and altered the dopaminergic system in various brain areas similar to the effect of amphetamine and cocaine, but did not produce addiction in a chronic study. In the present study, we investigated the protective effect of T. laurifolia on behavioural changes and alteration of the tyrosine hydroxylase expressions in the mesolimbic dopaminergic pathway in acute and chronic ethanol administration in adult male Wistar rats. The animals were divided into four groups i.e., control, ethanol, T. laurifolia (200 mg/kg, i.p.), and T. laurifolia (200 mg/kg, i.p.) with ethanol in both acute and chronic (30 days) administrations. The anxiety behaviour, exploratory behaviour, and addiction behaviour were tested and tyrosine hydroxylase expression alteration was determined. Chronic ethanol administration significantly (p < 0.01) induced addictive behaviour in the conditioned place preference (CPP) test and significantly (p < 0.01) decreased tyrosine hydroxylase expression in the nucleus accumbens. Chronic T. laurifolia administration alone did not cause any change in the behaviours and tyrosine hydroxylase expression. Interestingly, daily administration of T. laurifolia prior to ethanol administration prevented ethanol-induced addictive behaviour and significantly (p< 0.01) increased tyrosine hydroxylase expression in the nucleus accumbens. Therefore, it can be concluded from our results that daily pre-administration of T. laurifolia can protect against ethanol-induced addiction and a decrease in dopamine synthesis in the reward system of the mesolimbic dopaminergic pathway. © 2021 Sangpayap et al.