• Platelet Adenylyl Cyclase Activity;
  • Alcohol Dependence;
  • Marijuana Abuse;
  • Depression

Background There has been considerable interest in identifying biochemical markers indicative of a genetic predisposition to alcohol dependence (“trait markers”), as well as biochemical markers of recent alcohol drinking (“state markers”). Platelet adenylyl cyclase activity has been suggested as a trait and/or as a state marker related to alcohol dependence. We have now measured platelet adenylyl cyclase activity in more than 1400 well-characterized subjects, which allows us to investigate the influence of a broad range of factors on this activity.

Methods Subjects were recruited as part of the WHO/ISBRA Study on State and Trait Markers of Alcohol Use and Dependence and were interviewed by using the WHO/ISBRA Interview Schedule. Adenylyl cyclase activity (basal, cesium fluoride [CsF]-, forskolin- and Gpp(NH)p-stimulated activities) was measured in platelet samples that were obtained at the time of interview. Data were analyzed by multivariate regression analyses.

Results The multivariate analyses revealed that recent abstinence from alcohol was associated with diminutions in platelet adenylyl cyclase activities. A positive family history of alcohol dependence was associated with higher levels of adenylyl cyclase activities, and there was a significant interaction between the effect of alcohol consumption in the past month and family history of alcohol dependence; that is, the influence of alcohol consumption depended on whether the individual had a positive family history. A history of marijuana abuse also was associated with higher levels of platelet adenylyl cyclase activities, and a history of major depression was associated with lower levels of forskolin- and CsF-stimulated activities. Sex, race, and site of recruitment also affected some adenylyl cyclase activities, but there was no significant association of alcohol dependence or abuse with any of the platelet adenylyl cyclase activities.

Discussion The large population and extensive characterization of subjects in this study provided an advantage over previous studies in which only the association of a few individual factors with adenylyl cyclase activity was investigated. The results demonstrate that although platelet adenylyl cyclase activity could be useful as a trait marker of alcohol dependence, its reliability in this regard is diminished by the influence of recent alcohol drinking and other variables. The associations between platelet adenylyl cyclase activities and marijuana abuse, as well as a history of depression, suggest that it may be worthwhile to study the genetic association of adenylyl cyclases (e.g., polymorphisms in the genes that code for particular adenylyl cyclase isoforms) with a predisposition to depression as well as to alcohol or marijuana abuse/dependence.