CSF gamma-aminobutyric acid in alcoholics and control subjects

Alteration of glutamate/GABA balance during acute alcohol withdrawal in emergency department: a prospective analysis

AIMS

Animal studies suggest that in alcohol withdrawal the balance of neurotransmitters gamma aminobutyric acid (GABA) and glutamate is altered. To test this in humans, we aimed to measure plasma levels of glutamate, GABA and glutamate/GABA ratio in alcoholic patients presenting with complicated AWS with the same values in non-alcohol abuser/dependent controls and to determine prognostic factors for severe withdrawal.

METHODS

88 patients admitted to the emergency room for acute alcohol intoxication (DSM-IV) were prospectively included. Measurements of GABA and glutamate were performed on admission (Time 1, T1) and after 12 ± 2 h (T2). The experimental group (EG) was composed of 23 patients who presented at T2 with a severe AWS. The control group (CG) consisted of healthy subjects paired with the EG (gender and age). Logistic regression was performed in order to compare associated clinical and biological variables that could predict severe withdrawal.

RESULTS

The concentration of GABA in the EG at T1 was significantly lower than that in the CG. The concentration of glutamate in the EG at T1 was significantly higher than that in the CG. The glutamate/GABA ratio in the EG at T1 was significantly higher than the ratio in the CG. With a multivariate logistic regression model, glutamate level at admission remained the only criterion identified as a predictor of AWS at 12 h.

CONCLUSION

Decreased synthesis of GABA and increased synthesis of glutamate might be related to withdrawal symptoms experienced on brutal cessation of chronic alcohol intake.

Regulation of anxiety during the postpartum period

Healthy mother-infant interactions are critical for the physical, cognitive, and psychological development of offspring. Such interactions rely on numerous factors, including a positive maternal emotional state. However, many postpartum women experience emotional dysregulation, often involving elevated anxiety. Neuroendocrine factors contributing to the onset of postpartum anxiety symptoms are mostly unknown, but irregularities in hypothalamic-pituitary-adrenal axis function, reduced prolactin and oxytocin signaling, or parturitional withdrawal of ovarian, placental and neural steroids could contribute to anxiety in susceptible women. Although the causes of initial onset are unclear, postpartum anxiety can be mitigated by recent contact with infants. Numerous neurochemical systems, including oxytocin, prolactin, GABA, and norepinephrine mediate this anxiolytic effect of infant contact. Insight into the etiology of postpartum anxiety disorders, and how contact with infants helps counter existing anxiety dysregulation, will surely facilitate the diagnosis and treatment of postpartum women at risk for, or experiencing, an anxiety disorder.

Cortical gamma-aminobutyric acid levels and the recovery from ethanol dependence: preliminary evidence of modification by cigarette smoking

BACKGROUND

Gamma-aminobutyric acid (GABA)ergic adaptations contribute to the neurobiology of ethanol dependence and withdrawal. Clinical data suggest that tobacco smoking attenuates alcohol withdrawal symptoms. This study's objective was to measure time-dependent cortical GABA levels with sobriety in ethanol-dependent patients with mild to moderate withdrawal severity, controlling for alcoholism-related neurotoxicity and smoking.

METHODS

Proton magnetic resonance spectroscopy (MRS) was used to measure occipital cortical N-acetylaspartate (NAA), glutamate plus glutamine, and GABA in 12 ethanol-dependent men at approximately 1 week and 1 month of medication-free sobriety on an inpatient unit. Eight healthy men were studied once. The tissue composition of the MRS volume was determined.

RESULTS

Adjusting for less white matter in patients, GABA differed insignificantly between ethanol-dependent patients (smokers plus nonsmokers) and healthy subjects. In early sobriety, nonsmoking patients had more GABA than did smoking patients, but by 1 month, GABA decreased in nonsmokers without changing in smokers. Smoking was associated with increased glutamate plus glutamine in patients and healthy subjects, adjusting for NAA levels.

CONCLUSIONS

These data do not show that deficits in cortical GABA contribute directly to acute ethanol withdrawal. If smoking prevents withdrawal-related changes in cortical GABA systems, it may contribute to comorbidity of alcoholism and tobacco smoking.

Basic aspects of GABA-transmission in alcoholism, with particular reference to GABA-transaminase

Neuronal dysfunction is the neurobiological basis for alcoholic behaviour, and ethanol craving seems related to hypofunction of the GABA-ergic activity. Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system (CNS). In several studies, GABA has been shown to be an important target of ethanol in the CNS, partly, as a consequence of damage to membrane-bound enzymes and receptors. GABA is involved in mediating pre- and post-synaptic inhibition of neuronal activity. It is speculated that the initial excitatory effects of ethanol may be due to inhibition of GABA-ergic activity whereas the sedative effects of the higher doses may be mediated by the activation of this inhibitory system. In the CNS, GABA is synthesised from glutamic acid by the enzyme glutamate decarboxylase (GAD) and catabolized into succinic semialdehyde by the enzyme GABA-transaminase (GABA-T), which are pyridoxal phosphate (PLP) dependent enzymes. Platelet GABA-T was characterized as being similar to central GABA-T. Inhibition of GABA-T with certain potent and selective compounds markedly increases the levels of brain GABA. Experimentally, acute ethanol treatment does not alter GABA-T activity whereas chronic treatment produces an increase in the activity, though, with some reservations since a bimodal effect has been found in chronically ethanol-treated rats. Thus, as it will be discussed below, it may be suggested that GABA-T inhibitors (e.g. vigabatrin) could have a potential role in the treatment of alcoholism and in some of the problems of ethanol withdrawal and of other drugs of abuse. Related studies on metabolism and concentrations of GABA are also promising and show a greater increase in our understanding of the aetiology and treatment of ethanol dependence and withdrawal. In general, this article also reviews both the animal and clinical observations in the field of alcoholism with regard to the GABA system.

Levels of gamma-aminobutyric acid in cerebrospinal fluid and plasma during alcohol withdrawal

Aminobutyric acid (GABA) is implicated in the biochemical pathophysiology of alcohol intoxication, dependence and withdrawal. We therefore measured GABA in both cerebrospinal fluid (CSF) and plasma from 14 male alcohol-dependent patients during acute alcohol withdrawal (day 1) and again after 21 days of inpatient treatment (day 21). Plasma GABA levels on admission correlated with indices of liver function. When corrected for differences in liver function, plasma levels of GABA levels on day 1 were significantly higher than on day 21. CSF GABA concentrations were also significantly higher during withdrawal compared with concentrations after 3 weeks of abstinence. The change in plasma GABA levels correlated significantly with the change in CSF GABA levels, although there was no correlation between plasma and CSF levels at either time. These findings demonstrate that changes in CSF GABA may be reflected in plasma GABA, and they highlight the potential importance of the GABA system in alcohol dependence and withdrawal.

Low platelet gamma-aminobutyrate aminotransferase and monoamine oxidase activities in chronic alcoholic patients

The activities of gamma-aminobutyrate aminotransferase (GABA-T) and monoamine oxidase (MAO) were estimated in blood platelets from 25 male chronic alcoholics and from 27 healthy male volunteers without histories of alcohol abuse. Based on clinical criteria, the alcoholics were classified into type 1 or type 2 alcoholism. The activity of GABA-T was found to be lower both in type 1 and type 2 alcoholics than in healthy volunteers. With regard to MAO, the platelet activity was found to be significantly lower only in type 2 alcoholics in concordance with previous reports. No significant correlation was found between the activities of GABA-T and MAO in the blood platelets of healthy volunteers. The inhibitory effect of 400 mM ethanol on the platelet MAO activity increased with decreasing concentrations of the substrate phenylethylamine. The degree of inhibition of ethanol on the platelet MAO activity, however, did not differ significantly between alcoholics and controls.

Cerebrospinal fluid variables among alcoholics lack seasonal variation

Seasonal influences on indices of serotonergic function, including cerebrospinal fluid (CSF) concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA), have been reported in psychiatric patients and healthy volunteers. We examined seasonal differences in CSF concentrations of 5-HIAA among 135 alcoholics admitted to a research ward who had a lumbar puncture. No significant seasonal differences were found for either CSF concentrations of 5-HIAA or CSF concentrations of other monoamine metabolites or peptides. The possible explanations for these negative findings are discussed.

CSF GABA in depressed patients and normal controls

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) has been implicated in the pathophysiology of depression. Therefore, we examined cerebrospinal fluid (CSF) levels of GABA in depressed patients (N = 25) and normal controls (N = 20). There was no significant difference between the groups. However, among the depressed patients the subgroup of unipolar melancholic patients (N = 13) had significantly lower CSF levels of GABA than the rest of the depressed patients (N = 12). There was no significant difference for CSF levels of GABA between depressed patients who were (N = 14) or were not (N = 11) cortisol non-suppressors. It was of interest that among the controls there was a significant negative correlation between CSF levels of GABA and CSF levels of norepinephrine.