Psychopathology in alcohol withdrawal: relationship to alpha2-adrenoceptor function

Rasgrf2 controls noradrenergic involvement in the acute and subchronic effects of alcohol in the brain

RATIONALE

Alcohol addiction is a major psychiatric disease, and yet, the underlying molecular adaptations in the brain remain unclear. Recent evidence suggests a functional role for the ras-specific guanine-nucleotide releasing factor 2 (Rasgrf2) in alcoholism. Rasgrf2(-/-) mice consume less alcohol and show entirely absent dopamine responses to an alcohol challenge compared to wild types (WT).

OBJECTIVE

In order to further investigate how Rasgrf2 modifies the acute and subchronic effects of alcohol in the brain, we investigated its effects on the noradrenergic and serotonergic systems.

METHODS

We measured noradrenaline and serotonin activity in the brain by in vivo microdialysis and RNA expression by chip analysis and RT-PCR after acute and sub-chronic alcohol exposure in Rasgrf2(-/-) and WT mice.

RESULTS

In vivo microdialysis showed a significantly reduced noradrenergic response and an absent serotonergic response in the nucleus accumbens (NAcc) and caudate putamen (CPu) after an alcohol challenge in Rasgrf2(-/-) mice. A co-expression analysis showed that there is a high correlation between Rasgrf2 and α2 adrenoceptor RNA expression in the ventral striatum in naïve animals. Accordingly, we further assessed the role of Rasgrf2 in the response of the noradrenergic system to subchronic alcohol exposure. A decrease in β1 adrenoceptor gene expression was seen in Rasgrf2(+/+), but not Rasgrf2(-/-) mice following alcohol exposure. Conversely, alcohol resulted in a decrease in both β2 and α2 adrenoceptor gene expression in knockout but not WT Rasgrf2 mice.

CONCLUSIONS

These findings suggest that adaptations in the noradrenergic system contribute to the Rasgrf2 enhanced risk of alcoholism.

Outcome predictors in substance use disorders

Given the heterogeneous nature of substance abuse, it is notable that several predictors of response are independent of the primary drug of abuse or the treatment setting [208]. Although the strength of the relationship of predictor to outcome varies, the following factors have been identified consistently: severity of dependence or withdrawal; psychiatric comorbidity; substance-related problems; motivation (abstinence commitment); length of treatment; negative affective states; cognitive factors; personality traits and disorders; coping skills; multiple substance abuse; contingency contracting or coercion; genetic factors; sleep architecture; urges and craving; self-efficacy; and economic and social factors. Although it is well known that severity of dependence (including polysubstance abuse), serious psychiatric comorbidity, and social problems are associated with poor treatment response, only recently has research examined the efficacy of intervention strategies that specifically address these problems. Adequate treatment of psychiatric comorbidity and improvement in social, economic, and family functioning lead to better treatment outcomes. The development of specific techniques to enhance self-efficacy, motivation, coping skills, and functioning in the community are concrete examples of how the identification of factors associated with positive outcomes has led to the development of new treatments. Despite significant accomplishments, the field is left with many unanswered questions. Although several biologic markers, such as neuroendocrine response and sleep architecture, show promise as outcome predictors, it is not known whether these are critical factors in the initiation of substance use or its progression to dependence. Determining whether biologic markers are epiphenomena reflecting the amount and duration of substance abuse or are fundamental to the pathophysiology of dependence is a matter of urgent concern. With some exceptions, identification of biologic predictors has not led to innovative therapies. One of these exceptions is the development of naltrexone for the treatment of alcoholism, which was based in a solid theoretical rationale and followed by hypothesis-driven experiments. Similar opportunities should emerge from current basic science and clinical research. The application of pharmacogenetic techniques to the field of addiction also holds great promise. As future studies are undertaken, researchers and clinicians must be mindful that differences in outcome predictors across drugs of abuse and treatments may emerge as subgroups of individuals with addictive disorders and new therapies are identified. There is already evidence that early onset alcoholism is associated with poor response under some circumstances, yet may be a predictor of response to targeted pharmacotherapy with ondansetron [64, 112]. As the ability to subtype disorders based on meaningful biologic differences grows, it is anticipated that several relevant outcome predictors that are specific for pharmacotherapy will emerge.

Alcohol and withdrawal: from animal research to clinical issues

The withdrawal syndrome in alcohol-dependent patients appears to be a major stressful event whose intensity increases with repetition of detoxifications according to a kindling process. Disturbances in the balance between excitatory and inhibitory neural processes are reflected in a perturbed physical state while disturbances in the balance between positive and negative reinforcements are reflected in a perturbed mood state. Our purpose is to link the different behavioral outcomes occurring during withdrawal with specific biological brain mechanisms from the animal to the human being. Better understanding of the various biological mechanisms underlying withdrawal from alcohol will be the key to design and to apply appropriate pharmaceutical management, together with appropriate therapy aimed at inducing protracted abstinence.

Basal and isoproterenol-stimulated cyclic-adenosine monophosphate levels in mouse hippocampus and lymphocytes during alcohol tolerance and withdrawal

AIMS

Basal and isoproterenol-stimulated levels of cyclic-adenosine monophosphate (cAMP) were investigated in the brain (hippocampus) and in the lymphocytes of mice rendered tolerant to, and physically dependent on, ethanol.

METHODS

cAMP was measured with radioimmunoassay. Tolerance to, and physical dependence on, ethanol were induced by a 14-day ingestion of ethanol in drinking water. Upon replacing ethanol with water, ethanol withdrawal was precipitated and measured by the intensity of withdrawal-induced hyperexcitability and seizures.

RESULTS

Basal (non-stimulated) levels of cAMP - both in the hippocampus and in the lymphocytes - were significantly reduced in the alcohol-drinking tolerant and physically dependent animals, but significantly increased 24 h after the onset of withdrawal. Isoproterenol resulted in a dose-dependent stimulation of cAMP in all groups investigated (control, tolerant/physically dependent, withdrawal), however, the magnitude of isoproterenol-induced net increase was significantly lower in the tolerant, and higher in the ethanol-withdrawn, animals.

CONCLUSIONS

The major finding of the present experiments is that there was a significant positive correlation between basal cAMP levels in brain and lymphocytes versus the intensity of withdrawal hyperexcitability in ethanol-addicted mice.

Extremely long recovery time for the sedative effect of clonidine in male type 1 alcohol-dependent subjects in full sustained remission

The possible relation between alpha-2-adrenoceptor function-as assessed by changes in systolic and diastolic blood pressure and heart rate, as well as level of sedation, after administration of clonidine (2.0 microg/kg, i.v.)-and length of time of alcohol dependence or duration of remission was investigated in 17 male subjects with alcohol dependence in full sustained remission. Six healthy males were used as control subjects. The clonidine-induced scores for level of sedation were found to correlate with duration of time in remission (r = 0.60; P <.02). Median split of duration of remission revealed that subjects with short-term (2 +/- 1 years) duration of remission had significantly lower scores for clonidine-induced level of sedation than the scores for both subjects with long-term (12 +/- 5 years) duration of remission (P <.004) and control subjects (P <.02). There was also a significant correlation between duration of remission and values for clonidine-induced reduction of systolic blood pressure (r = 0.51; P <.05). Results indicate an extremely long recovery period in some aspects of alpha-2-adrenoceptor function, especially for clonidine-induced increase in level of sedation, with a normalization time of 4 to 5 years.

Plasma catecholamines in ethanol tolerance and withdrawal in mice

Plasma levels of catecholamines (noradrenaline and adrenaline) as well as the ratio of the two catecholamines were measured in experimental mice during various stages of acute and chronic ethanol treatment. Acute intraperitoneal (i.p.) ethanol administration and acute per os (p.o.) ethanol ingestion resulted in a similar elevation of the plasma levels of both catecholamines. During the development of ethanol tolerance/dependence (ingestion of drinking water containing ethanol for 14 days), plasma catecholamine concentrations returned to the control levels. During subsequent ethanol withdrawal, a highly significant increase was observed in plasma noradrenaline. The withdrawal-associated elevation of plasma adrenaline was also significant; however, the rise in plasma noradrenaline during withdrawal appeared to be higher than that found for adrenaline. Thus, the ratio of plasma noradrenaline to adrenaline was higher during withdrawal, and this ratio also exhibited an association with the severity of ethanol withdrawal symptoms. Since plasma noradrenaline derives to a great extent from the sympathetic nervous system--and the alcohol withdrawal syndrome is characterized by symptoms of overactivity of this system--a positive correlation may exist between noradrenaline and the severity of withdrawal symptomatology.

Cardiovascular responses to clonidine in alcohol withdrawal: are they related to psychopathology and mental well-being?

The possible relationships between alpha-2-adrenoceptor function, as assessed by blood pressure, heart rate, and sedative responses to clonidine (CLON; 1.5 microg/kg, i.v.), and psychopathology and mental well-being were investigated in 19 patients with alcohol-dependence in the early withdrawal period (days 1 and 7). An age-matched control group was used (n=17). CLON-induced maximum reduction of systolic blood pressure was less day 1 in the alcohol-dependent patients compared to controls. CLON was found to induce less sedation at day 7 compared to day 1 and to controls. No relationships were seen between the parameters for alpha-2-adrenoceptor function and psychopathology and mental well-being. These findings suggest that CLON-induced changes in blood pressures and heart rate reflect the cardiovascular situation in alcohol withdrawal and not aspects of behavior.