Agmatine reverses ethanol consumption in rats: Evidences for an interaction with imidazoline receptors

Alcohol is one of the most widely abused recreational drugs, largely linked with serious health and social concerns. However, the treatment options for alcohol-use disorders have limited efficacy and exhibit a range of adverse drug reactions. Large numbers of preclinical studies have projected a biogenic amine, agmatine as a promising potential treatment option for drug addiction, including alcoholism. In the present study, administration of agmatine (20-40 mg/kg, i.p.) resulted in significant inhibition of ethanol self-administration in the right p-VTA in operant conditioning paradigm. Further, acute intracranial administration of agmatine (20 and 40 μg/rat) significantly reduced the ethanol consumption in the two bottle choice paradigm. Agmatine is degraded to putrescine and guanido-butanoic acid by the enzyme agmatinase and diamine oxidase respectively and inhibition of these enzymes results in augmentation of endogenous agmatine. In the present study, diamine oxidase inhibitor, aminoguanidine and agmatinase inhibitor, arcaine were used to block the agmatine metabolic pathways to increase brain agmatine levels. Drugs that augment endogenous agmatine levels like L-arginine (80 μg/rat, i.c.v.) or arcaine (50 μg/rat, i.c.v.) and aminoguanidine (25 μg/rat, i.c.v.) also reduced the ethanol consumption following their central administration. The pharmacological effect of agmatine on ethanol consumption was potentiated by imidazoline receptor agonists, I₁ agonist moxonidine (25 μg/rat, i.c.v.), and imidazoline I₂ agonist, 2-BFI (10 μg/rat, i.c.v.) and was blocked by imidazoline I₁ antagonist, efaroxan (10 μg/rat, i.c.v.), and I₂ antagonist, idazoxan (4 μg/rat, i.c.v.) at their ineffective doses per se. Thus, our result suggests the involvement of imidazoline I₁ and I₂ receptors in agmatine induced inhibition of ethanol consumption in rats.