An Initial Study of the Relationship Between Platelet Adenylyl Cyclase Activity and Alcohol Use Disorder Criteria

Predictors of high ethanol consumption in RIIbeta knock-out mice: assessment of anxiety and ethanol-induced sedation

BACKGROUND

Genetic and pharmacological evidence suggests that the cyclic adenosine monophosphate-dependent protein kinase A pathway modulates neurobiological responses to ethanol. Mutant mice lacking the RIIbeta subunit of protein kinase A (RIIbeta(-/-)) are resistant to ethanol-induced sedation and drink significantly more ethanol than littermate wild-type mice (RIIbeta(+/+)). We determined whether high ethanol intake by the RIIbeta(-/-) mice on alternate genetic backgrounds is reliably predicted by high basal levels of anxiety or resistance to the sedative effects of ethanol.

METHODS

Two-bottle choice procedures and a battery of behavioral tests (elevated plus maze, open-field activity, and zero maze) were used to assess voluntary ethanol consumption and basal levels of anxiety in RIIbeta(-/-) and RIIbeta(+/+) mice on either a C57BL/6J or a 129/SvEv x C57BL/6J genetic background. Additionally, ethanol-induced sedation and blood ethanol levels were determined in RIIbeta(-/-) and RIIbeta(+/+) mice after intraperitoneal injection of ethanol (3.8 g/kg).

RESULTS

RIIbeta(-/-) mice on both genetic backgrounds consumed more ethanol and had a greater preference for ethanol relative to RIIbeta(+/+) mice. However, RIIbeta(-/-) mice showed reduced basal levels of anxiety when maintained on the C57BL/6J background but showed increased anxiety when maintained on the 129/SvEv x C57BL/6J background. Consistent with prior research, RIIbeta(-/-) mice were resistant to the sedative effects of ethanol, regardless of the genetic background. Finally, RIIbeta(-/-) and RIIbeta(+/+) mice showed similar blood ethanol levels.

CONCLUSIONS

These results indicate that high ethanol consumption is associated with resistance to the sedative effects of ethanol but that basal levels of anxiety, as well as ethanol metabolism, do not reliably predict high ethanol drinking by RIIbeta(-/-) mice.

Regulation and role of adenylyl cyclase isoforms

At least nine closely related isoforms of adenylyl cyclases (ACs), the enzymes responsible for the synthesis of cyclic AMP (cAMP) from ATP, have been cloned and characterized in mammals. Depending on the properties and the relative levels of the isoforms expressed in a tissue or a cell type at a specific time, extracellular signals received through the G-protein-coupled receptors can be differentially integrated. The present review deals with various aspects of such regulations, emphasizing the role of calcium/calmodulin in activating AC1 and AC8 in the central nervous system, the potential inhibitory effect of calcium on AC5 and AC6, and the changes in the expression pattern of the isoforms during development. A particular emphasis is given to the role of cAMP during drug and ethanol dependency and to some experimental limitations (pitfalls in the interpretation of cellular transfection, scarcity of the invalidation models, existence of complex macromolecular structures, etc).

Tissue specificity and physiological relevance of various isoforms of adenylyl cyclase

The present review focuses on the potential physiological regulations involving different isoforms of adenylyl cyclase (AC), the enzymatic activity responsible for the synthesis of cAMP from ATP. Depending on the properties and the relative level of the isoforms expressed in a tissue or a cell type at a specific time, extracellular signals received by the G protein-coupled receptors can be differently integrated. We report here on various aspects of such regulations, emphasizing the role of Ca(2+)/calmodulin in activating AC1 and AC8 in the central nervous system, the potential inhibitory effect of Ca(2+) on AC5 and AC6, and the changes in the expression pattern of the isoforms during development. A particular emphasis is given to the role of cAMP during drug dependence. Present experimental limitations are also underlined (pitfalls in the interpretation of cellular transfection, scarcity of the invalidation models, and so on).

Platelets and psychiatry: lessons learned from old and new studies

Platelets play an important role not only in hemostasis but also in the pathophysiology of coronary artery disease. The complex interactions among the vascular endothelium, platelets, and blood components are one of the most exciting research areas today. This review addresses some fundamentals of platelet physiology and examines why platelets are interesting probes for neurophysiology. Results of current studies suggest that platelets are affected by diverse stressors, including psychological ones, and that platelets offer an interesting vantage point for understanding the neurophysiology of various psychiatric disorders. We also describe how platelets have been used for various types of research, including studies of stress associated with cardiovascular disease and studies of platelets in psychopharmacological research. Finally, we examine some of the psychiatric literature related to platelets; these studies range from case studies from the 1920s to contemporary experimental studies.

Biological phenotypes associated with individuals at high risk for developing alcohol-related disorders. Part 2

This paper reviews comparisons of populations at higher and lower risk for alcoholism on biological phenotypes. The results of studies must be considered in the context of the research methods used including the need for large, carefully defined samples and longitudinal designs. Comparisons of children of alcoholics and controls have revealed potentially important differences on level of response to alcohol, cognitive attributes and differences in alcohol-metabolizing and other enzyme systems responsible for various aspects of the body's reaction to alcohol. Many opportunities for future research in this area exist, including large-scale, longitudinal studies that simultaneously evaluate multiple domains of influence, and searches for candidate genes or other biological material that will simplify procedures and increase the accuracy of measurement.