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Phosphatidylinositide 3-kinases (PI3Ks) are intracellular signal transducer enzymes that recruit protein kinase B (aka Akt) to the cell membrane, the subsequent activation of which regulates many cellular functions. PI3K/Akt activity is up-regulated within mesocorticolimbic structures in animal models of alcoholism, but less is known regarding PI3K/Akt activity in animal models of cocaine addiction. Given that prefrontal cortex (PFC) is grossly dysregulated in addiction, we studied how cocaine affects protein indices of PFC PI3K/Akt activity in rat and mouse models and examined the relevance of PI3K activity for cocaine-related learning. Immunoblotting of mouse medial PFC at 3 weeks withdrawal from a cocaine-sensitization regimen (seven injections of 30 mg/kg, intraperitoneal [IP]) revealed increased kinase activity, as did immunoblotting of tissue from the ventral PFC of rats with a history of long-access intravenous cocaine self-administration (0.25 mg/0.1 mL infusion; 10 days of 6 h/d cocaine access). Interestingly, increased Akt phosphorylation was observed in rat ventromedial PFC at both 3- and 30-day withdrawal only in animals re-exposed to cocaine-associated cues. A conditioned place-preference paradigm in mice and a cue-elicited drug-seeking test in rats were conducted to determine the functional relevance for elevated PI3K activity for addiction-related behavior. In both cases, an intra-PFC infusion of the PI3K inhibitor wortmannin (50μM) reduced drug-seeking behavior. Taken together, this cross-species, interdisciplinary, study provides convincing evidence that cocaine history produces an enduring increase in PI3K/Akt-dependent signaling within the more ventral aspect of the PFC that is relevant to behavioral reactivity to drug-associated cues/contexts. As such, PI3K inhibitors may well serve as an effective strategy for reducing drug cue reactivity and craving in cocaine addiction.

BackgroundProtein kinase C epsilon (PKCε) is emerging as a potential target for the development of pharmacotherapies to treat alcohol use disorders, yet little is known regarding how a history of a highly prevalent form of drinking, binge alcohol intake, influences enzyme priming or the functional relevance of kinase activity for excessive alcohol intake.MethodsImmunoblotting was employed on tissue from subregions of the nucleus accumbens (NAc) and the amygdala to examine both idiopathic and binge drinking-induced changes in constitutive PKCε priming. The functional relevance of PKCε translocation for binge drinking and determination of potential upstream signaling pathways involved were investigated using neuropharmacologic approaches within the context of two distinct binge drinking procedures, drinking in the dark and scheduled high alcohol consumption.ResultsBinge alcohol drinking elevated p(Ser729)-PKCε levels in both the NAc and the central nucleus of the amygdala (CeA). Moreover, immunoblotting studies of selectively bred and transgenic mouse lines revealed a positive correlation between the propensity to binge drink alcohol and constitutive p(Ser729)-PKCε levels in the NAc and CeA. Finally, neuropharmacologic inhibition of PKCε translocation within both regions reduced binge alcohol consumption in a manner requiring intact group 1 metabotropic glutamate receptors, Homer2, phospholipase C, and/or phosphotidylinositide-3 kinase function.ConclusionsTaken together, these data indicate that PKCε signaling in both the NAc and CeA is a major contributor to binge alcohol drinking and to the genetic propensity to consume excessive amounts of alcohol.

Despite the fact that binge alcohol drinking (intake resulting in blood alcohol concentrations (BACs) 80 mg% within a 2-h period) is the most prevalent form of alcohol-use disorders (AUD), a large knowledge gap exists regarding how this form of AUD influences neural circuits mediating alcohol reinforcement. The present study employed integrative approaches to examine the functional relevance of binge drinking-induced changes in glutamate receptors, their associated scaffolding proteins and certain signaling molecules within the central nucleus of the amygdala (CeA). A 30-day history of binge alcohol drinking (for example, 4-5 g kg(-1) per 2 h(-1)) elevated CeA levels of mGluR1, GluN2B, Homer2a/b and phospholipase C (PLC) β3, without significantly altering protein expression within the adjacent basolateral amygdala. An intra-CeA infusion of mGluR1, mGluR5 and PLC inhibitors all dose-dependently reduced binge intake, without influencing sucrose drinking. The effects of co-infusing mGluR1 and PLC inhibitors were additive, whereas those of coinhibiting mGluR5 and PLC were not, indicating that the efficacy of mGluR1 blockade to lower binge intake involves a pathway independent of PLC activation. The efficacy of mGluR1, mGluR5 and PLC inhibitors to reduce binge intake depended upon intact Homer2 expression as revealed through neuropharmacological studies of Homer2 null mutant mice. Collectively, these data indicate binge alcohol-induced increases in Group1 mGluR signaling within the CeA as a neuroadaptation maintaining excessive alcohol intake, which may contribute to the propensity to binge drink.

Background Alcohol increases the expression of Group 1 metabotropic glutamate receptors ( mGlu Rs) and their associated scaffolding protein Homer2 and stimulates phosphatidylinositol 3-kinase ( PI3 K) within the nucleus accumbens ( NAC). Moreover, functional studies suggest that NAC Group 1 mGlu R/ Homer2/ PI3 K signaling may be a potential target for pharmacotherapeutic intervention in alcoholism. Methods Immunoblotting was conducted to examine the effects of alcohol consumption under drinking-in-the-dark ( DID) procedures on Group 1 m Glu R-associated proteins in C57 BL/6 J ( B6) mice. Follow-up behavioral studies examined the importance of Group 1 m Glu R/ Homer2/ PI3 K signaling within the NAC shell for limited-access alcohol drinking. Finally, immunoblotting examined whether the NAC expression of Group 1 m Glu R-associated proteins is a genetic correlate of high alcohol drinking using a selectively bred high DID ( HDID-1) mouse line. Results Limited-access alcohol drinking under DID procedures up-regulated NAC shell Homer2 levels, concomitant with increases in m Glu R5 and NR2B. Intra- NAC shell blockade of m Glu R5, Homer2, or PI3K signaling, as well as transgenic disruption of the Homer binding site on m Glu R5, decreased alcohol consumption in B6 mice. Moreover, transgenic disruption of the Homer binding site on m Glu R5 and Homer2 deletion both prevented the attenuating effect of m Glu R5 and PI3K blockade upon intake. Finally, the basal NAC shell protein expression of m Glu R1 and Homer2 was increased in offspring of HDID-1 animals. Conclusions Taken together, these data further implicate Group 1 m Glu R signaling through Homer2 within the NAC in excessive alcohol consumption. [ABSTRACT FROM AUTHOR]