Metabotropic Glutamate Receptor 5 Within Nucleus Accumbens Shell Modulates Environment-Elicited Cocaine Conditioning Expression.

Metabotropic Glutamate Receptor 5 within Nucleus Accumbens Shell modulates environment-elicited cocaine conditioning expression.

Pharmacol Biochem Behav. 2013 Jul 9;
Martínez-Rivera A, Rodríguez-Borrero E, Matías-Alemán M, Montalvo-Acevedo A, Guerrero-Figuereo K, Febo-Rodriguez LJ, Morales-Rivera A, Maldonado-Vlaar CS

The metabotropic glutamate receptors 5 (mGluRs5) within the Nucleus Accumbens (NAc) have been implicated in the modulation of psychostimulant reward. We hypothesized that blockade of mGluR5 within the NAc shell would impair cocaine conditioning in rats. For this study, animals were implanted with cannulae within the NAc shell, and separate groups were exposed to a multimodal environment within activity chambers that signaled cocaine (cocaine-paired) or saline (controls, cocaine-unpaired) injections. Prior to placing the animals in the chambers, rats received systemic intraperitoneal injections of saline or cocaine for 10 consecutive sessions. In the test session (D12), animals were exposed to the multimodal environment without any cocaine or saline pre-treatment. Before placing the rats in the chambers, separate groups of animals were infused within the NAc shell with 2.5, 12 or 25nmol/0.5?l/side of 2-methyl-6- (phenylethynyl) pyridine (MPEP), an antagonist of mGluR5 or with vehicle. Blockade of the mGluR5 subtype at a 2.5nmol dose showed no significant difference in either the ambulatory distance (AD) or the vertical plane move time (VPT). In contrast, mGluR5 blockade at 12nmol and 25nmol decreased conditioned locomotion in the cocaine-paired groups. An association of the environmental cues with the effects of cocaine implies the involvement of memory process during the conditioning response. Our results suggest that mGluR5 within the NAc shell could be modulating the expression of memory related to the association of environmental cues with the effects of cocaine. We suggest that mGluR5 could be taking into account to further studies related with cocaine exposure and cocaine addiction treatments. HubMed – addiction

Comparison of the Risks of Opioid Abuse or Dependence Between Tapentadol and Oxycodone: Results From a Cohort Study.

J Pain. 2013 Jul 10;
Cepeda MS, Fife D, Ma Q, Ryan PB

Tapentadol may have a lower abuse risk than other opioids because it has a relatively low affinity for the mu-opioid receptor. The aim of this retrospective cohort study was to compare the risk of opioid abuse between tapentadol immediate release (IR) and oxycodone IR using 2 claims databases (Optum and MarketScan). Subjects with no recent opioid use exposed to tapentadol IR or oxycodone IR in 2010 were followed for 1 year. The outcome was the proportion of subjects who developed opioid abuse, defined as subjects with International Classification of Diseases, 9th revision, codes for opioid abuse, addiction, or dependence. The relative odds of abuse were estimated using a logistic regression model with propensity-score stratification. The estimates from the 2 databases were pooled using a random effects model. There were 13,814 subjects in Optum (11,378 exposed to oxycodone, 2,436 exposed to tapentadol) and 25,553 in MarketScan (21,728 exposed to oxycodone, 3,825 exposed to tapentadol). The risk of abuse was higher in the oxycodone group than in the tapentadol group in each database. The pooled adjusted estimate for the odds of abuse was 65% lower with tapentadol than with oxycodone (odds ratio = .35, 95% confidence interval = .21-.58). The risk of receiving an abuse diagnosis with tapentadol was lower than the risk with oxycodone. Continued monitoring is warranted because opioid desirability can change over time.This study compared the risk of receiving an opioid abuse diagnosis between tapentadol and oxycodone in 2 U.S. claims databases. The risk of receiving an abuse diagnosis was lower with tapentadol during the year of follow-up. Opioid prescribers and patients must be aware of the risk of abuse associated with all opioids. HubMed – addiction

Varenicline modulates spatial working memory deficits in smokers with schizophrenia.

Schizophr Res. 2013 Jul 11;
Wing VC, Wass CE, Bacher I, Rabin RA, George TP

HubMed – addiction