Involvement of Purinergic P2X4 Receptors in Alcohol Intake of High-Alcohol-Drinking (HAD) Rats

Abstract

Background: The P2X4 receptor is thought to be involved in regulating alcohol-consuming behaviors and ethanol (EtOH) has been reported to inhibit P2X4 receptors. Ivermectin is an anti-parasitic agent that acts as a positive allosteric modulator of the P2X4 receptor. The current study examined the effects of systemically- and centrally-administered ivermectin on alcohol drinking of replicate lines of high-alcohol-drinking (HAD-1/HAD-2) rats, and the effects of lentiviral-delivered short-hairpin RNAs (shRNAs) targeting P2rx4 on EtOH intake of female HAD2 rats. Method: For the 1st experiment, adult male HAD-1 & HAD-2 rats were given 24-hr free-choice access to 15% EtOH vs. water. Dose-response effects of ivermectin (1.5 to 7.5 mg/kg i.p.) on EtOH intake were determined; the effects of ivermectin were then examined for 2% w/v sucrose intake over 5 consecutive days. In the 2nd experiment, female HAD-2 rats were trained to consume 15% EtOH under 2-hr limited access conditions, and dose-response effects of intracerebroventricular (ICV) administration of ivermectin (0.5 to 2.0 μg) were determined over 5 consecutive days. The 3rd experiment determined the effects of microinfusion of a lentivirus expressing P2rx4 shRNAs into the posterior ventral tegmental area (VTA) on 24-hr EtOH free-choice drinking of female HAD-2 rats. Results: The highest i.p. dose of ivermectin reduced alcohol drinking (30-45%) in both rat lines, but did not alter sucrose intake. HAD-2 rats appeared to be more sensitive than HAD1 rats to the effects of ivermectin. ICV administration of ivermectin reduced 2-hr limited access intake (∼35%) of female