In contrast, dose-dependent increases in rCBV were most pronounced in limbic regions, such that responses seen at see more 0.1 mg/kg nicotine in accumbens, hippocampus, amygdala, and several other limbic areas were not seen following 0.3 mg/kg nicotine. Finally, whereas profound tolerance was observed in many cortical regions after the second of two paired nicotine injections at either 0.1 or 0.3 mg/kg, subcortical limbic structures showed only a weak trend for tolerance. Lack of rCBV changes in animals receiving nicotine methiodide,
a quaternary nicotine analog that does not cross the blood-brain barrier, supports a direct neuronal effect of nicotine rather than an action on the vasculature. These data provide pharmacodynamic insight into the regional heterogeneity of nicotine tachyphylaxis development, which may be relevant to behavioral and
neurobiological mechanisms associated with repeated tobacco consumption. Neuropsychopharmacology AS1842856 (2011) 36, 2498-2512; doi:10.1038/npp.2011.139; published online 27 July 2011″
“Alcoholism and alcohol use disorders are characterized by several months to decades of heavy and problematic drinking, interspersed with periods of abstinence and relapse to heavy drinking. This alcohol-drinking phenotype was modeled using macaque monkeys to explore neuronal adaptations in the striatum, a brain region controlling habitual behaviors. Prolonged drinking with repeated abstinence narrowed the variability in daily intake, increased the amount find more of ethanol consumed in bouts, and led to higher blood ethanol concentrations more than twice the legal intoxication limit. After :the final abstinence period of this extensive drinking protocol, we found a selective increase in dendritic spine density and enhanced glutamatergic transmission in the putamen, but not in the caudate nucleus. Intrinsic
excitability of medium-sized spiny neurons was also enhanced in the putamen of alcohol-drinking monkeys in comparison with non-drinkers, and GABAeric transmission was selectively suppressed in the putamen of heavy drinkers. These morphological and physiological changes indicate a shift in the balance of inhibitory/excitatory transmission that biases the circuit toward an enduring increase in synaptic activation of putamen output as a consequence of prolonged heavy drinking/relapse. The resultant potential for increased putamen activation may underlie an alcohol-drinking phenotype of regulated drinking and sustained intoxication. Neuropsychopharmacology (2011) 36, 2513-2528; doi:10.1038/npp.2011.140; published online 27 July 2011″
“Genetic variation in AKTI may be associated with sensitivity to the psychotomimetic effects of cannabis as well as with increased risk for psychotic disorder following cannabis use. Investigation of the effect of this interaction on relevant intermediate phenotypes for psychosis, such as cognition, may help to clarify the underlying mechanism.