CSF GABA and neuropeptides in pathological gamblers and normal controls

Evidence for GABA-A receptor dysregulation in gambling disorder: correlation with impulsivity

As a behavioural addiction, gambling disorder (GD) provides an opportunity to characterize addictive processes without the potentially confounding effects of chronic excessive drug and alcohol exposure. Impulsivity is an established precursor to such addictive behaviours, and GD is associated with greater impulsivity. There is also evidence of GABAergic dysregulation in substance addiction and in impulsivity. This study therefore investigated GABA_A receptor availability in 15 individuals with GD and 19 healthy volunteers (HV) using [¹¹C]Ro15‐4513, a relatively selective α5 benzodiazepine receptor PET tracer and its relationship with impulsivity. We found significantly higher [¹¹C]Ro15‐4513 total distribution volume (V_T) in the right hippocampus in the GD group compared with HV. We found higher levels of the ‘Negative Urgency’ construct of impulsivity in GD, and these were positively associated with higher [¹¹C]Ro15‐4513 V_T in the amygdala in the GD group; no such significant correlations were evident in the HV group. These results contrast with reduced binding of GABAergic PET ligands described previously in alcohol and opiate addiction and add to growing evidence for distinctions in the neuropharmacology between substance and behavioural addictions. These results provide the first characterization of GABA_A receptors in GD with [¹¹C]Ro15‐4513 PET and show greater α5 receptor availability and positive correlations with trait impulsivity. This GABAergic dysregulation is potential target for treatment.

Similarities and Differences in Neurobiology

Substance addiction is a chronic, relapsing brain disease characterized by compulsive drug seeking and use despite harmful consequences. Non-substance addiction is defined recently that people may compulsively engage in an activity despite any negative consequences to their lives. Despite differences with respect to their addictive object, substance addiction and non-substance addiction may share similarities with respect to biological, epidemiological, clinical, genetic and other features. Here we review the similarities and differences in neurobiology between these two addictions with a focus on dopamine, serotonin, opioid, glutamate and norepinephrine systems. Studies suggest the involvement of all these systems in both substance addiction and non-substance addiction while differences may exist with respect to their contributions.

Neural and psychological underpinnings of gambling disorder: A review

Gambling disorder affects 0.4 to 1.6% of adults worldwide, and is highly comorbid with other mental health disorders. This article provides a concise primer on the neural and psychological underpinnings of gambling disorder based on a selective review of the literature. Gambling disorder is associated with dysfunction across multiple cognitive domains which can be considered in terms of impulsivity and compulsivity. Neuroimaging data suggest structural and functional abnormalities of networks involved in reward processing and top-down control. Gambling disorder shows 50-60% heritability and it is likely that various neurochemical systems are implicated in the pathophysiology (including dopaminergic, glutamatergic, serotonergic, noradrenergic, and opioidergic). Elevated rates of certain personality traits (e.g. negative urgency, disinhibition), and personality disorders, are found. More research is required to evaluate whether cognitive dysfunction and personality aspects influence the longitudinal course and treatment outcome for gambling disorder. It is hoped that improved understanding of the biological and psychological components of gambling disorder, and their interactions, may lead to improved treatment approaches and raise the profile of this neglected condition.

Anxiety in major depression and cerebrospinal fluid free gamma-aminobutyric acid

BACKGROUND

Low gamma-aminobutyric acid (GABA) is implicated in both anxiety and depression pathophysiology. They are often comorbid, but most clinical studies have not examined these relationships separately. We investigated the relationship of cerebrospinal fluid (CSF) free GABA to the anxiety and depression components of a major depressive episode (MDE) and to monoamine systems.

METHODS AND MATERIALS

Patients with a DSM-IV major depressive episode (N = 167: 130 major depressive disorder; 37 bipolar disorder) and healthy volunteers (N = 38) had CSF free GABA measured by gas chromatography mass spectroscopy. Monoamine metabolites were assayed by high performance liquid chromatography. Symptomatology was assessed by Hamilton depression rating scale.

RESULTS

Psychic anxiety severity increased with age and correlated with lower CSF free GABA, controlling for age. CSF free GABA declined with age but was not related to depression severity. Other monoamine metabolites correlated positively with CSF GABA but not with psychic anxiety or depression severity. CSF free GABA was lower in MDD compared with bipolar disorder and healthy volunteers. GABA levels did not differ based on a suicide attempt history in mood disorders. Recent exposure to benzodiazepines, but not alcohol or past alcoholism, was associated with a statistical trend for more severe anxiety and lower CSF GABA.

CONCLUSIONS

Lower CSF GABA may explain increasing severity of psychic anxiety in major depression with increasing age. This relationship is not seen with monoamine metabolites, suggesting treatments targeting the GABAergic system should be evaluated in treatment-resistant anxious major depression and in older patients.

Male gamblers have significantly greater salivary cortisol before and after betting on a horse race, than do female gamblers

Prevalence rates of gambling are influenced by gender. Among normative populations, hypothalamic-pituitary-adrenal (HPA) axis response to stress is affected by gender. However, pathological, compared to recreational, gamblers demonstrate perturbations in HPA activation in response to gambling stimuli. We examined whether there were gender differences in HPA response to gambling in a naturalistic setting among horse-race bettors and scratch-off lottery bettors. Salivary cortisol was collected from horse-race gamblers (n=32) and scratch-off lottery ticket players (n=39) before and after (0, 10, or 20 min) betting on a horse race at an off-track betting establishment. Salivary cortisol levels were significantly higher among men than among women, both prior to and following, betting on a horse race. Among women, but not men, there was a decline in salivary cortisol across time in scratch-off bettors, whereas women horse-race bettors maintained consistent low concentrations of salivary cortisol at every time point sampled. Together these data suggest that engaging in gambling may have different effects on stress responses of men, compared to women. Whether these gender differences in HPA activation contribute to gender-related differences in gambling behavior is the subject of ongoing investigation.

Pathological gambling: an update on neuropathophysiology and pharmacotherapy

Neurobiological research has shown the potential involvement of serotonergic, dopaminergic and opioid dysfunction in the pathophysiology of pathological gambling. In this review, we present current theories of the neuropathology of pathological gambling, paying particular attention to the role of the neural circuitry underlying motivation, reward, decision-making and impulsivity. This review also presents a literature review of current pharmacological treatment strategies for pathological gambling, such as selective serotonin reuptake inhibitors (SSRIs), opioid receptor antagonists, anti-addiction drugs and mood stabilizers, and also discusses the role of nonpharmacological interventions.A hypothetical model of the clinical subtypes of pathological gambling is presented, e.g. the impulsive subtype, the obsessive-compulsive subtype and the addictive subtype. This model attempts to integrate current knowledge in the field of pathological gambling regarding neuropathology, psychiatric co-morbidity, family history, genetics, course of illness, gender and response to pharmacological treatment. Finally, it is proposed that the existence of possible clinical subtypes of pathological gambling may provide a potential framework for matching the various subtypes with specific pharmacotherapies.

CSF cholecystokinin, γ-aminobutyric acid and neuropeptide Y in pathological gamblers and healthy controls

The sulphated cholecystokinin (CCK) octapeptide (CCK-8S), the CCK tetrapeptide (CCK-4), neuropeptide Y (NPY) and gamma-aminobutyric acid (GABA) were determined in cerebrospinal fluid (CSF) obtained from 11 pathological male gamblers and 11 healthy male controls. Compared with healthy controls, pathological male gamblers displayed higher concentrations of CCK-8S, CCK-4 and GABA (but not NPY). A gradient with decreasing concentrations from the first to the third 6-ml CSF fraction was found for CCK-8S, CCK-4 and NPY, but only in pathological gamblers. Disrupted gradients were found for GABA and for NPY in healthy controls. Given that CCK is a modulator of dopamine in the reward process, the increase in CCK-8S and CCK-4 is not unexpected. The high level of GABA in pathological gamblers is in conformity with a compensatory inhibitory action on noradrenergic neurons. The CSF gradient of CCK-8S and CCK-4 in pathological male gamblers (but not healthy controls) might indicate a difference in diurnal variation. The results obtained are in line with an altered CCK and GABA function in pathological gambling.

Pathological gambling: a comprehensive review of biobehavioral findings

In this review, findings of biobehavioral research into pathological gambling (PG) are discussed, focusing on neuropsychological, psychophysiological, neuroimaging, neurochemical and genetic studies. Neuropsychological studies indicate deficiencies in certain executive functions. Psychophysiological studies indicate that arousal in PG is of importance when reward is present. Neuroimaging studies point to abnormalities in brain functioning. Recent research into the neurochemistry of PG indicates that abnormalities exist in different neurotransmitter systems. Finally, genetic studies indicate the existence of abnormal dopamine receptor genes in PG. Methodological and theoretical factors that may explain discrepancies between studies include differences in screening and assessment, heterogeneity of gambling problems and different underlying cognitive or motivational mechanisms. Results from the PG studies fit in with recent theoretical models of addiction and PG, which stress the involvement of brain reward pathways, neurotransmitter abnormalities, the frontal cortex and the psychophysiological stress system. A framework for future studies is suggested, indicating the need for studies that integrate knowledge from different research areas, and that employ stricter diagnostic screening methods and inclusion of clinical control groups.

The additive effect of neurotransmitter genes in pathological gambling

As access to gambling increases there is a corresponding increase in the frequency of addiction to gambling, known as pathological gambling. Studies have shown that a number of different neurotransmitters are affected in pathological gamblers and that genetic factors play a role. Polymorphisms at 31 different genes involved in dopamine, serotonin, norepinephrine, GABA and neurotransmitters were genotyped in 139 pathological gamblers and 139 age, race, and sex-matched controls. Multivariate regression analysis was used with the presence or absence of pathological gambling as the dependent variable, and the 31 coded genes as the independent variables. Fifteen genes were included in the regression equation. The most significant were the DRD2, DRD4, DAT1, TPH, ADRA2C, NMDA1, and PS1 genes. The r(2) or fraction of the variance was less than 0.02 for most genes. Dopamine, serotonin, and norepinephrine genes contributed approximately equally to the risk for pathological gambling. These results indicate that genes influencing a range of brain functions play an additive role as risk factors for pathological gambling. Multi-gene profiles in specific individuals may be of assistance in choosing the appropriate treatment.

Casino gambling increases heart rate and salivary cortisol in regular gamblers

BACKGROUND

Although the effects of gambling on cardiovascular parameters have been documented, no data exists describing the effect of gambling on stress hormone secretion. Our study investigated the effect of gambling on heart rate and salivary cortisol in a casino environment.

METHODS

Ten male gamblers participated in both an experimental and control session. In the experimental session, gamblers played a game of blackjack using their own money. Gamblers played cards in the same setting during the control condition; however, the game was played for accumulation of points rather than money. Heart rate and endocrine parameters were recorded at baseline, 30 min, and 60 min following commencement of each session, and again at completion of the game.

RESULTS

Heart rate increased significantly from baseline to 30 min in the experimental session and remained elevated for the remainder of the recording period. Salivary cortisol was raised at 30 min and further elevated at 60 min during gambling, then returned to control levels following completion of the game.

CONCLUSIONS

These data indicate that gambling in a "real life" situation produces increases in salivary cortisol levels that accompany increased cardiovascular activity. Such effects may contribute to the development of gambling addiction.

The nature and treatment of excessive gambling

Satisfactory models of the nature and treatment of excessive gambling must incorporate behavioural, cognitive, emotional and physiological findings. The acquisition of gambling behaviour is apparently influenced by social exposure and financial reinforcement. Continuation is promoted by partial reinforcement schedules and biased cognitions. Excessive gambling also involves changes in the individual's internal state, including physiological arousal, euphoria, distraction and perceived control. These effects might depend on the prior characteristics of the individual. Treatment should remove conditioned triggers, establish alternative means of financial and internal regulation, and reduce the individual's need for the financial and subjective rewards provided by gambling. Treatment goals and resources are discussed.

CSF neuropeptide Y in alcoholics and normal controls

Neuropeptide Y is found in brain tissue. In dogs it has been shown to enhance activation of the hypothalamic-pituitary-adrenal axis by corticotropin-releasing hormone. It is localized in certain catecholamine neurons and to some extent colocalized with somatostatin. Disturbances of the central noradrenergic system may underlie some forms of alcoholism. Therefore, we compared male alcoholics and normal controls on cerebrospinal fluid (CSF) levels of neuropeptide Y. There was no significant difference between the two groups for neuropeptide Y. There was also no significant difference for CSF levels of growth hormone releasing hormone. However, there were significant positive correlations between CSF levels of neuropeptide Y and CSF levels of corticotropin-releasing hormone, somatostatin, and growth hormone releasing hormone.

Cerebrospinal fluid levels of somatostatin, corticotropin-releasing hormone and corticotropin in alcoholism

Reduced brain and cerebrospinal fluid (CSF) levels of somatostatin, corticotropin-releasing hormone (CRH) and corticotropin (ACTH) have been reported among neuropsychiatric patients with cognitive dysfunction. Alcoholism is a disorder in which associated neuropsychiatric disorders occur. Therefore, we compared CSF levels of somatostatin, CRH and ACTH in alcoholics (n = 100) and normal controls (n = 30). There were no significant differences between the groups in concentrations of the 3 peptides. Moreover, there were no significant correlations between concentrations of the peptides in CSF and computed tomographic measures of the size of brain ventricles. There were, however, significant correlations between CSF concentrations of CRH and ACTH and between CSF concentrations of CRH and somatostatin in both the alcoholic and control groups.