Alterations in ethanol-induced accumbal transmission after acute and long-term zinc depletion

Alcoholism is subject to extensive research, but the role of changes in metabolism caused by alcohol consumption has been poorly investigated. Zinc (Zn(2+) ) deficiency is a common metabolic aberration among alcoholics and Zn(2+) influences the function of ligand-gated ion channels, known pharmacological targets of ethanol (EtOH). Here, we investigate whether manipulation of extracellular levels of Zn(2+) modulates EtOH-induced increases of dopamine (DA) output, as measured by in vivo microdialysis in the rat, and whether voluntary EtOH consumption is altered by Zn(2+) deficiency. Our findings show that the Zn(2+) -chelating agent tricine slowly raises DA levels when perfused in the nucleus accumbens (nAc), whereas the more potent Zn(2+) chelator TPEN reduces DA levels. We also show that pre-treatment with either tricine or TPEN blocks the EtOH-induced DA elevation. Chronic Zn(2+) deficiency induced by a Zn(2+) -free diet did not affect EtOH consumption, but excitatory transmission, assessed by striatal field-potential recordings in the nAc shell, was significantly modulated both by Zn(2+) -free diet and by EtOH consumption, as compared with the EtOH naïve controls. The present study indicates that Zn(2+) influences EtOH's interaction with the brain reward system, possibly by interfering with glycine receptor and GABAA receptor function. This also implies that Zn(2+) deficiency among alcoholics may be important to correct in order to normalize important aspects of brain function.