Enhanced dopamine D2 receptor function in hypothalamus and corpus striatum: their role in liver, plasma and in vitro hepatocyte ALDH regulation in ethahol treated rats

Abstract

Dopamine D 2 receptors are involved in ethanol self-administration behavior and also suggested to mediate the onset and offset of ethanol drinking. In the present study, we investigated dopamine (DA) content and Dopamine D 2 (DA D 2 ) receptors in the hypothalamus and corpus striatum of ethanol treated rats and aldehyde dehydrogenase (ALDH) activity in the liver and plasma of ethanol treated rats and in vitro hepatocyte cultures. Hypothalamic and corpus striatal DA content decreased significantly (P \ 0.05, P \ 0.001 respectively) and homovanillic acid/ dopamine (HVA/DA) ratio increased significantly (P \ 0.001) in ethanol treated rats when compared to control. Scatchard analysis of [ 3 H] YM-09151-2 binding to DA D 2 receptors in hypothalamus showed a significant increase (P \ 0.001) in B max without any change in K d in ethanol treated rats compared to control. The K d of DA D 2 receptors significantly decreased (P \ 0.05) in the corpus striatum of ethanol treated rats when compared to control. DA D 2 receptor affinity in the hypothalamus and corpus striatum of control and ethanol treated rats fitted to a single site model with unity as Hill slope value. The in vitro studies on hepatocyte cultures showed that 10 -5 M and 10 -7 M DA can reverse the increased ALDH activity in 10% ethanol treated cells to near control level. Sulpiride, an antagonist of DA D 2 , reversed the effect of dopamine on 10% ethanol induced ALDH activity in hepatocytes. Our results showed a decreased dopamine concentration with enhanced DA D 2 receptors in the hypothalamus and corpus striatum of ethanol treated rats. Also, increased ALDH was observed in the plasma and liver of ethanol treated rats and in vitro hepatocyte cultures with 10% ethanol as a compensatory mechanism for increased aldehyde production due to increased dopamine metabolism. A decrease in dopamine concentration in major brain regions is coupled with an increase in ALDH activity in liver and plasma, which contributes to the tendency for alcoholism. Since the administration of 10 -5 M and 10 -7 M DA can reverse the increased ALDH activity in ethanol treated cells to near control level, this has therapeutic application to correct ethanol addicts from addiction due to allergic reaction observed in aldehyde accumulation.

Psilocybin-assisted treatment for alcohol dependence: A proof-of-concept study

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Comorbid alcohol dependence disorder may be related to aldehyde dehydrogenase 2 (ALDH2) and alcohol dehydrogenase 1B (ADH1B) in bipolarIIdisorder, but only toALDH2in bipolar I disorder, in Han Chinese

“…The frequencies of these alleles have also been reported to be higher in alcohol dependent persons than in the general population in other East Asians: Han Chinese in Taiwan , Koreans , and Japanese . The involvement of ALDH has been reported to differ from that of ADH in AD .…”