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Resistin, founding member of the resistin-like molecule (RELM) hormone family, is secreted selectively from adipocytes and induces liver-specific antagonism of insulin action, thus providing a potential molecular link between obesity and diabetes. Crystal structures of resistin and RELMbeta reveal an unusual multimeric structure. Each protomer comprises a carboxy-terminal disulfide-rich beta-sandwich "head" domain and an amino-terminal alpha-helical "tail" segment. The alpha-helical segments associate to form three-stranded coiled coils, and surface-exposed interchain disulfide linkages mediate the formation of tail-to-tail hexamers. Analysis of serum samples shows that resistin circulates in two distinct assembly states, likely corresponding to hexamers and trimers. Infusion of a resistin mutant, lacking the intertrimer disulfide bonds, in pancreatic-insulin clamp studies reveals substantially more potent effects on hepatic insulin sensitivity than those observed with wild-type resistin. This result suggests that processing of the intertrimer disulfide bonds may reflect an obligatory step toward activation.

Activity of the mesolimbic dopaminergic system was investigated in rats withdrawn from chronic ethanol administration by single-cell extracellular recordings from dopaminergic neurons of the ventrotegmental area, coupled with antidromic identification from the nucleus accumbens, and by microdialysis-technique experiments in the nucleus accumbens. Spontaneous firing rates, spikes per burst, and absolute burst firing but not the number of spontaneously active neurons were found drastically reduced; whereas absolute and relative refractory periods increased in rats withdrawn from chronic ethanol treatment as compared with chronic saline-treated controls. Consistently, dopamine outflow in the nucleus accumbens and its acid metabolites were reduced after abruptly stopping chronic ethanol administration. All these changes, as well as ethanol-withdrawal behavioral signs, were reversed by ethanol administration. This reversal suggests that the abrupt cessation of chronic ethanol adminitration plays a causal role in the reduction of mesolimbic dopaminergic activity seen in the ethanol-withdrawal syndrome. Results indicate that during the ethanol-withdrawal syndrome the mesolimbic dopaminergic system is tonically reduced in activity, as indexed by electrophysiological and biochemical criteria. Considering the role of the mesolimbic dopaminergic system in the reinforcing properties of ethanol, the depressed activity of this system during the ethanol-withdrawal syndrome may be relevant to the dysphoric state associated with ethanol withdrawal in humans.Alcoholism is a major economic, social, and health problem (1). Indeed, alcohol is the most abused substance after nicotine in the Western world, and alcohol abuse and dependence ranked first of all psychiatric disorders in lifetime prevalence rates (2). As for many other abused drugs, this compulsive behavior seems to be elicited and maintained by the powerful reinforcing properties of the drug. Dopamine (DA) is one of the major candidates suggested to mediate reinforcement in animals (3): accordingly, rats will self-stimulate when electrodes are placed near DA neurons in the ventrotegmental area (VTA) (4, 5), and many addicting drugs, including ethanol, increase DA release in the nucleus accumbens (6) and increase DA firing in the VTA (7).The ethanol-withdrawal syndrome begins after cessation of prolonged ethanol administration. A symptom common to withdrawal syndromes, regardless of the substance abused, is the dysphoria associated with absence of the drug. In spite of the evidence linking an increase in dopaminergic transmission to the hedonic properties of ethanol (8), no study has tested in vivo whether the ethanol-withdrawal syndrome is associated with a decline in mesolimbic dopaminergic activity. However, a reduction of DA turnover has been reported The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.(9),...