A gene-by-sex interaction for nicotine reward: evidence from humanized mice and epidemiology.

It has been proposed that vulnerability to nicotine addiction is moderated by variation at the µ-opioid receptor locus (OPRM1), but results from human studies vary and prospective studies based on genotype are lacking. We have developed a humanized mouse model of the most common functional OPRM1 polymorphism rs1799971_A>G (A118G). Here we use this model system together with a cohort of German youth to examine the role of the OPRM1 A118G variation on nicotine reward. Nicotine reinforcement was examined in the humanized mouse model using i.v. self-administration. Male (n=17) and female (n=26) mice homozygous either for the major human A allele (AA) or the minor G allele (GG) underwent eight daily 2 h sessions of nicotine self-administration. Furthermore, male (n=104) and female (n=118) subjects homozygous for the A allele or carrying the G allele from the Mannheim Study of Children at Risk were evaluated for pleasurable and unpleasant experiences during their initial smoking experience. A significant sex-by-genotype effect was observed for nicotine self-administration. Male 118GG mice demonstrated higher nicotine intake than male 118AA mice, suggesting increased nicotine reinforcement. In contrast, there was no genotype effect in female mice. Human male G allele carriers reported increased pleasurable effects from their first smoking experience, as compared to male homozygous A, female G and female homozygous A allele carriers. The 118G allele appears to confer greater sensitivity to nicotine reinforcement in males, but not females.

Monoamine oxidase A polymorphism moderates stability of attention problems and susceptibility to life stress during adolescence.

Attention problems affect a substantial number of children and adolescents and are predictive of academic underachievement and lower global adaptive functioning. Considerable variability has been observed with regard to the individual development of attention problems over time. In particular, the period of adolescence is characterized by substantial maturation of executive functioning including attentional processing, with the influence of genetic and environmental factors on individual trajectories not yet well understood. In the present investigation, we evaluated whether the monoamine oxidase A functional promoter polymorphism, MAOA-LPR, plays a role in determining continuity of parent-rated attention problems during adolescence. At the same time, a potential effect of severe life events (SLEs) was taken into account. A multi-group path analysis was used in a sample of 234 adolescents (149 males, 85 females) who took part in an epidemiological cohort study at the ages of 11 and 15 years. Attention problems during early adolescence were found to be a strong predictor of attention problems in middle adolescence. However, in carriers of the MAOA-LPR low-activity variant (MAOA-L), stability was found to be significantly higher than in carriers of the high-activity variant (MAOA-H). Additionally, only in MAOA-L carriers did SLEs during adolescence significantly impact on attention problems at the age of 15 years, implying a possible gene × environment interaction. To conclude, we found evidence that attention problems during adolescence in carriers of the MAOA-L allele are particularly stable and malleable to life stressors. The present results underline the usefulness of applying a more dynamic GxE perspective.

Neuro-endocrine and neuropsychological outcome after aneurysmal subarachnoid hemorrhage (aSAH): a prospective cohort study.

OBJECTIVE: Neuropsychological sequelae are common after aneurysmal subarachnoid hemorrhage (aSAH) and may be associated with or caused by supposed hypothalamic-pituitary dysfunction. We evaluated the incidence of neuro-endocrine and neuropsychological deficits after aSAH and their interrelations in a standardized manner. METHODS: 26 patients (20 females) were prospectively screened for neuro-endocrine and neuropsychological deficits 3 and 6 months after aSAH. We measured GH, IGF-1, prolactin, LH, FSH, estradiol, TSH, fT4, total T3, testosterone, ACTH as well as cortisol before and after ACTH-stimulation. Neuropsychological analysis covered verbal comprehension, short term and working memory, visuospatial construction, figural memory, psychomotor speed, attention, and concentration. RESULTS: After 3 months central hypogonadism was observed in 2 patients accompanied by central hypothyroidism in 1 male subject. Central hypogonadism resolved spontaneously after 6 months in both. After 3 months, neuropsychological deficits were detected in 57% of the examined patients (44% attention deficits, 38% memory impairment, 12% psychomotor deficits). Neuropsychological deficits were still present in 53% after 6 months. CONCLUSION: We found a low prevalence of neuro-endocrine and a high prevalence of neuropsychological deficits in patients 3 and 6 months after aSAH. Thus, the absent co-incidence of central hormonal and psychological dysfunction leaves a causal association questionable.