Gamma-hydroxybutyric acid: neurobiology and toxicology of a recreational drug

Beta-Hydroxybutyric Acid as a Template for the X-ray Powder Diffraction Analysis of Gamma-Hydroxybutyric Acid

In this paper, we report the possibility of using the X-ray powder diffraction (XRPD) technique to detect gamma-hydroxybutyric acid (GHB) in the form of its sodium salt in different beverages, but because it is not possible to freely buy GHB, beta-hydroxybutyric acid (BHB) and its sodium salt (NaBHB) were used as a model to fine-tune an X-ray diffraction method for the qualitative analysis of the sodium salt of GHB. The method requires only a small quantity of beverage and an easy sample preparation that consists only of the addition of NaOH to the drink and a subsequent drying step. The dry residue obtained can be easily analyzed with XRPD using a single-crystal X-ray diffractometer, which exploits its high sensitivity and allows for very fast pattern collection. Several beverages with different NaBHB:NaOH molar ratios were tested, and the results showed that NaBHB was detected in all drinks analyzed when the NaBHB:NaOH molar ratio was 1:50, using a characteristic peak at very low 2θ values, which also permitted the detection of its presence in complex beverage matrices. Moreover, depending on the amount of NaOH added, shifting and/or splitting of the characteristic NaBHB salt peak was observed, and the origin of this behavior was investigated.

Medication-induced central sleep apnea: a unifying concept

Medication-induced central sleep apnea (CSA) is one of the eight categories of causes of CSA but in the absence of awareness and careful history may be misclassified as primary CSA. While opioids are a well-known cause of respiratory depression and CSA, non-opioid medications including sodium oxybate, baclofen, valproic acid, gabapentin, and ticagrelor are less well-recognized. Opioids-induced respiratory depression and CSA are mediated primarily by µ-opioid receptors, which are abundant in the pontomedullary centers involved in breathing. The non-opioid medications, sodium oxybate, baclofen, valproic acid, and gabapentin, act upon brainstem gamma-aminobutyric acid (GABA) receptors, which co-colonize with µ-opioid receptors and mediate CSA. The pattern of ataxic breathing associated with these medications is like that induced by opioids on polysomnogram. Finally, ticagrelor also causes periodic breathing and CSA by increasing central chemosensitivity and ventilatory response to carbon dioxide. Given the potential consequences of CSA and the association between some of these medications with mortality, it is critical to recognize these adverse drug reactions, particularly because discontinuation of the offending agents has been shown to eliminate CSA.

Effect of Repeated Administration of ɣ-Valerolactone (GVL) and GHB in the Mouse: Neuroadaptive Changes of the GHB and GABAergic System

BACKGROUND

Gamma-hydroxybutyric acid (GHB) at low dosages has anxiolytic effects and promotes REM sleep and low-wave deep sleep. In the U.S., the legal form of GHB is prescribed to adults suffering from narcolepsy-associated cataplexy; the sodium salt of GHB is reserved for alcohol-addiction treatment. GHB is also a molecule of abuse and recreational use, it is a controlled substance in several countries, so gamma-valerolactone (GVL) has frequently been used as a legal substitute for it. GHB's abuse profile is most likely attributable to its anxiolytic, hypnotic, and euphoric properties, as well as its widespread availability and inexpensive/low cost on the illicit market.

METHODS

Our study is focused on evaluating the potential effects on the mouse brain after repeated/prolonged administration of GHB and GVL at a pharmacologically active dose (100 mg/kg) through behavioral study and immunohistochemical analysis using the markers tetraspanin 17 (TSPAN17), aldehyde dehydrogenase 5 (ALDH5A1), Gamma-aminobutyric acid type A receptor (GABA-A), and Gamma-aminobutyric acid type B receptor (GABA-B).

RESULTS

Our findings revealed that prolonged administration of GHB and GVL at a pharmacologically active dose (100 mg/kg) can have effects on a component of the mouse brain, the intensity of which can be assessed using immunohistochemistry. The findings revealed that long-term GHB administration causes a significant plastic alteration of the GHB signaling system, with downregulation of the putative binding site (TSPAN17) and overexpression of ALDH5A1, especially in hippocampal neurons. Our findings further revealed that GABA-A and GABA-B receptors are downregulated in these brain locations, resulting in a greater decrease in GABA-B expression.

CONCLUSIONS

The goal of this study, from the point of view of forensic pathology, is to provide a new methodological strategy for better understanding the properties of this controversial substance, which could help us better grasp the unknown mechanism underlying its abuse profile.

The CaMKII-dependent phosphorylation of GABAB receptors in the nucleus accumbens was involved in cocaine-induced behavioral sensitization in rats

BACKGROUND

Previous studies have established that the regulation of prolonged, distal neuronal inhibition by the GABA_B heteroreceptor (GABA_B R) is determined by its stability, and hence residence time, on the plasma membrane.

AIMS

Here, we show that GABA_B R in the nucleus accumbens (NAc) of rats affects the development of cocaine-induced behavioral sensitization by mediating its perinucleus internalization and membrane expression.

MATERIALS & METHODS

By immunofluorescent labeling, flow cytometry analysis, Co-immunoprecipitation and open field test, we measured the role of Ca²⁺ /calmodulin-dependent protein kinase II (CaMKII) to the control of GABA_B R membrane anchoring and cocaine induced-behavioral sensitization.

RESULTS

Repeated cocaine treatment in rats (15 mg/kg) significantly decreases membrane levels of GABA_B1 R and GABA_B2 R in the NAc after day 3, 5 and 7. The membrane fluorescence and protein levels of GABA_B R was also decreased in NAc GAD₆₇ ⁺ neurons post cocaine (1 μM) treatment after 5 min. Moreover, the majority of internalized GABA_B1 Rs exhibited perinuclear localization, a decrease in GABA_B1 R-pHluroin signals was observed in cocaine-treated NAc neurons. By contrast, membrane expression of phosphorylated CaMKII (pCaMKII) post cocaine treatment was significantly increased after day 1, 3, 5 and 7. Baclofen blocked the cocaine induced behavioral sensitization via inhibition of cocaine enhanced-pCaMKII-GABA_B1 R interaction.

CONCLUSION

These findings reveal a new mechanism by which pCaMKII-GABA_B R signaling can promote psychostimulant-induced behavioral sensitization.

Repurposing of substances with lactone moiety for the treatment of γ-Hydroxybutyric acid and γ-Butyrolactone intoxication through modulating paraoxonase and PPARγ

GHB and GBL are highly accessible recreational drugs of abuse with a high risk of adverse effects and mortality while no specific antidotes exist. These components can also be found in the clinical setting, beverages, and cosmetic products, leading to unwanted exposures and further intoxications. As the structural analogue of GABA, GHB is suggested as the primary mediator of GHB/GBL effects. We further suggest that GBL might be as critical as GHB in this process, acting through PPARγ as its receptor. Moreover, PPARγ and PON (i.e., the GHB-GBL converting enzyme) can be targeted for GHB/GBL addiction and intoxication, leading to modulation of the GHB-GBL balance and blockage of their effects. We suggest that repurposing substances with lactone moiety such as bacterial lactones, sesquiterpene lactones, and statins might lead to potential therapeutic options as they occupy the active sites of PPARγ and PON and interfere with the GHB-GBL balance. In conclusion, this hypothesis improves the GHB/GBL mechanism of action, suggests potential therapeutic options, and highlights the necessity of classifying GBL as a controlled substance.

Metabolic Alterations Associated with γ-Hydroxybutyric Acid and the Potential of Metabolites as Biomarkers of Its Exposure

γ-Hydroxybutyric acid (GHB) is an endogenous short chain fatty acid that acts as a neurotransmitter and neuromodulator in the mammalian brain. It has often been illegally abused or misused due to its strong anesthetic effect, particularly in drug-facilitated crimes worldwide. However, proving its ingestion is not straightforward because of the difficulty in distinguishing between endogenous and exogenous GHB, as well as its rapid metabolism. Metabolomics and metabolism studies have recently been used to identify potential biomarkers of GHB exposure. This mini-review provides an overview of GHB-associated metabolic alterations and explores the potential of metabolites for application as biomarkers of GHB exposure. For this, we discuss the biosynthesis and metabolism of GHB, analytical issues of GHB in biological samples, alterations in metabolic pathways, and changes in the levels of GHB conjugates in biological samples from animal and human studies. Metabolic alterations in organic acids, amino acids, and polyamines in urine enable discrimination between GHB-ingested animals or humans and controls. The potential of GHB conjugates has been investigated in a variety of clinical settings. Despite the recent growth in the application of metabolomics and metabolism studies associated with GHB exposure, it remains challenging to distinguish between endogenous and exogenous GHB. This review highlights the significance of further metabolomics and metabolism studies for the discovery of practical peripheral biomarkers of GHB exposure.

A New Psychoactive Substance, Gamma Hydroxybutyrate (GHB): A Case Report

Gamma Hydroxybutyrate (GHB) is a central nervous system depressant effecting GABA-B receptors. GHB is taken along with other psychoactive substances like alcohol, cocaine, ecstasy, and amphetamines especially during parties. Due to the fact that it has been linked to sexual assault, GHB has drawn attention in recent years. This substance is often taken by youngsters and results in euphoric states of mind, signs of relief, easiness in communication, increases in sexual appetite, and experiences of different states of mind. Dizziness, hypotension, bradycardia, nauseation, and vomiting are typical toxication symptoms of GHB. Also, epileptic seizures, respirotary depression, and deaths have been reported as a result of taking GHB. It is widely known that the use of GHB in our country has increased gradually. This case report is important as it summarizes the anamnesis, penetration, and clinical symptoms of GHB. In order to prevent the use of GHB, it would be appropriate to develop psycho-education methodologies, establish legislative regulations, and include GHB tests in substance screening analyses.

[Knockout Drugs: Diagnostics in the Emergency Unit and Clinical Practice]

Knockout Drugs: Diagnostics in the Emergency Unit and Clinical Practice Abstract. Every now and then, physicians are challenged with date rape drugs. If there is a suspicion of substance administration, the question of involving forensic medicine is commonly raised. In obscure situations or questionable offences, however, patients may wish for an initial diagnosis in the emergency department or the private practice. The physicians are often greatly challenged by the variety of substances, the limited analytical methods and difficulties with the interpretion of results. The major goal of this article is to present diagnostic options including their limitations. An overview of frequently involved substances is provided. Particular focus will be placed on practical aspects, including questions regarding pre-analytics and health insurance coverage.

Prospective Investigation of the Performance of 2 Gamma-Hydroxybutyric Acid Tests: DrugCheck GHB Single Test and Viva-E GHB Immunoassay

BACKGROUND

Gamma-hydroxybutyric acid (GHB) is a recreational drug with central nervous system depressing effects that is often abused. A urine GHB point-of-care test can be of great diagnostic value. The objective of this prospective study was to determine the performance of the new DrugCheck GHB Single Test and the Viva-E GHB immunoassay for urine samples in emergency department patients.

METHODS

Patients presented to the emergency department of the OLVG hospital in Amsterdam with a Glasgow Coma Scale score <15 and potential drug of abuse intoxication were included in the study. Between June 2016 and October 2017, 375 patients were included. Using the DrugCheck GHB Single Test (Express Diagnostics Int'l, Blue Earth, MN) and the Viva-E GHB immunoassay (Siemens Healthineers, The Hague, the Netherlands), patients' urine samples were tested for GHB (cutoff for a positive result, 10 or 50 mcg/mL GHB). To ensure quality, the results obtained were compared with those generated using a validated gas chromatography method. The tests were considered reliable if specificity and sensitivity were both >90%. Possible cross-reactivity with ethanol was investigated by analyzing ethanol concentrations in patients' samples.

RESULTS

Seventy percentage of the included patients was men, and the median age was 34 years old. The DrugCheck GHB Single Test's specificity and sensitivity were 90.0% and 72.9%, respectively, and using 50 mcg/mL as a cutoff value, its specificity and sensitivity improved to 96.7% and 75.0%, respectively. Serum and urine ethanol levels in the false-positive group were significantly higher compared with those in the true-negative group. The specificity and sensitivity of the Viva-E GHB immunoassay (cutoff value of 50 mcg/mL and excluding samples with ethanol levels ≥2.0 g/L) were 99.4% and 93.5%, respectively.

CONCLUSIONS

The DrugCheck GHB Single Test's specificity was sufficient, whereas its sensitivity was poor, making it unsuitable for use at point-of-care. Contrarily, using 50 mcg/mL as the cutoff value and excluding samples with ethanol levels ≥2.0 g/L, the Viva-E GHB immunoassay showed acceptable results to detect clinically relevant GHB intoxications.

Alcohol Interaction with Cocaine, Methamphetamine, Opioids, Nicotine, Cannabis, and γ-Hydroxybutyric Acid

Millions of people around the world drink alcoholic beverages to cope with the stress of modern lifestyle. Although moderate alcohol drinking may have some relaxing and euphoric effects, uncontrolled drinking exacerbates the problems associated with alcohol abuse that are exploding in quantity and intensity in the United States and around the world. Recently, mixing of alcohol with other drugs of abuse (such as opioids, cocaine, methamphetamine, nicotine, cannabis, and γ-hydroxybutyric acid) and medications has become an emerging trend, exacerbating the public health concerns. Mixing of alcohol with other drugs may additively or synergistically augment the seriousness of the adverse effects such as the withdrawal symptoms, cardiovascular disorders, liver damage, reproductive abnormalities, and behavioral abnormalities. Despite the seriousness of the situation, possible mechanisms underlying the interactions is not yet understood. This has been one of the key hindrances in developing effective treatments. Therefore, the aim of this article is to review the consequences of alcohol's interaction with other drugs and decipher the underlying mechanisms.

Interpreting γ-hydroxybutyrate concentrations for clinical and forensic purposes

INTRODUCTION

γ-Hydroxybutyric acid is an endogenous substance, a therapeutic agent, and a recreational drug of abuse. This psychoactive substance acts as a depressant of the central nervous system and is commonly encountered in clinical and forensic practice, including impaired drivers, poisoned patients, and drug-related intoxication deaths.

OBJECTIVE

The aim of this review is to assist clinical and forensic practitioners with the interpretation of γ-hydroxybutyric acid concentrations in blood, urine, and alternative biological specimens from living and deceased persons.

METHODS

The information sources used to prepare this review were PubMed, Scopus, and Web-of-Science. These databases were searched using keywords γ-hydroxybutyrate (GHB), blood, urine, alternative specimens, non-conventional biological matrices, saliva, oral fluid, sweat, hair, vitreous humor (VH), brain, cerebrospinal fluid (CSF), dried blood spots (DBS), breast milk, and various combinations thereof. The resulting 4228 references were screened to exclude duplicates, which left 1980 articles for further consideration. These publications were carefully evaluated by taking into account the main aims of the review and 143 scientific papers were considered relevant. Analytical methods: The analytical methods used to determine γ-hydroxybutyric acid in blood and other biological specimens make use of gas- or liquid-chromatography coupled to mass spectrometry. These hyphenated techniques are accurate, precise, and specific for their intended purposes and the lower limit of quantitation in blood and other specimens is 0.5 mg/L or less. Human pharmacokinetics: GHB is rapidly absorbed from the gut and distributes into the total body water compartment. Only a small fraction of the dose (1-2%) is excreted unchanged in the urine. The plasma elimination half-life of γ-hydroxybutyric acid is short, being only about 0.5-0.9 h, which requires timely sampling of blood and other biological specimens for clinical and forensic analysis. Endogenous concentrations of GHB in blood: GHB is both an endogenous metabolite and a drug of abuse, which complicates interpretation of the laboratory results of analysis. Moreover, the concentrations of GHB in blood and other specimens tend to increase after sampling, especially in autopsy cases. This requires the use of practical "cut-off" concentrations to avoid reporting false positive results. These cut-offs are different for different biological specimen types. Concentrations of GHB in clinical and forensic practice: As a recreational drug GHB is predominantly used by young males (94%) with a mean age of 27.1 years. The mean (median) and range of concentrations in blood from apprehended drivers was 90 mg/L (82 mg/L) and 8-600 mg/L, respectively. The concentration distributions in blood taken from living and deceased persons overlapped, although the mean (median) and range of concentrations were higher in intoxication deaths; 640 mg/L (280 mg/L) and 30-9200 mg/L, respectively. Analysis of GHB in alternative specimens: All biological fluids and tissue containing water are suitable for the analysis of GHB. Examples of alternative specimens discussed in this review are CSF, saliva, hair strands, breast milk, DBS, VH, and brain tissue.

CONCLUSIONS

Body fluids for the analysis of GHB must be obtained as quickly as possible after a poisoned patient is admitted to hospital or after a person is arrested for a drug-related crime to enhance chances of detecting the drug. The sampling of urine lengthens the window of detection by 3-4 h compared with blood samples, but with longer delays between last intake of GHB and obtaining specimens, hair strands, and/or nails might be the only option. In postmortem toxicology, the concentrations of drugs tend to be more stable in bladder urine, VH, and CSF compared with blood, because these sampling sites are protected from the spread of bacteria from the gut. Accordingly, the relationship between blood and urine concentrations of GHB furnishes useful information when drug intoxication deaths are investigated.

Drug-drug interactions in the treatment for alcohol use disorders: A comprehensive review

Drug interactions are one of the most common causes of side effects in polypharmacy. Alcoholics are a category of patients at high risk of pharmacological interactions, due to the presence of comorbidities, the concomitant intake of several medications and the pharmacokinetic and pharmacodynamic interferences of ethanol. However, the data available on this issue are limited. These reasons often frighten clinicians when prescribing appropriate pharmacological therapies for alcohol use disorder (AUD), where less than 15% of patients receive an appropriate treatment in the most severe forms. The data available in literature regarding the relevant drug-drug interactions of the medications currently approved in United States and in some European countries for the treatment of AUD (benzodiazepines, acamprosate, baclofen, disulfiram, nalmefene, naltrexone and sodium oxybate) are reviewed here. The class of benzodiazepines and disulfiram are involved in numerous pharmacological interactions, while they are not conspicuous for acamprosate. The other drugs are relatively safe for pharmacological interactions, excluding the opioid withdrawal syndrome caused by the combination of nalmefene or naltrexone with an opiate medication. The information obtained is designed to help clinicians in understanding and managing the pharmacological interactions in AUDs, especially in patients under multi-drug treatment, in order to reduce the risk of a negative interaction and to improve the treatment outcomes.

Intoxication with GHB/GBL: characteristics and trends from ambulance-attended overdoses

BACKGROUND

Overdoses from so-called "club drugs" (GHB/GBL) have become a more frequent cause of overdoses attended by ambulance services. Given its availability, affordability, and lack of awareness of risks, there is a common misconception among users that the drug is relatively safe.

METHODS

This study reviewed ambulance records in Bergen, Norway between 2009 and 2015 for cases of acute poisonings, particularly from suspected GHB/GBL intoxication.

RESULTS

In total, 1112 cases of GHB and GBL poisoning were identified. GHB was suspected for 995 (89%) of the patients. Men made up the majority of the cases (n = 752, 67.6%) with a median age of 27 years old. Temporal trends for GHB/GBL overdoses displayed a late-night, weekend pattern. The most frequent initial symptoms reported were unconsciousness, or reduced consciousness. Most of the patients required further treatment and transport. During the period from 2009 to 2015, there was a nearly 50% decrease in GHB/GBL overdoses from 2013 to 2014.

DISCUSSION

The characteristics of GHB/GBL overdose victims shed light on this patient group. The decrease in incidence over the years may be partly due to a legal ban on GBL in Norway, declared in 2010. It may also be due to an increase in the use of MDMA/ecstasy.

CONCLUSION

The review of ambulance records on the prehospital treatment of overdoses can be beneficial in monitoring, preparing, and prevention efforts aimed to benefit this vulnerable group.

Pharmacological Treatment in γ-Hydroxybutyrate (GHB) and γ-Butyrolactone (GBL) Dependence: Detoxification and Relapse Prevention

The misuse of γ-hydroxybutyrate (GHB) for recreational purposes has resulted in an increase in GHB-related problems such as intoxications, dependence and withdrawal in several countries in Europe, Australia and the US over the last decade. However, prevalence rates of misuse of GHB and its precursor, γ-butyrolactone (GBL), are still relatively low. In this qualitative review paper, after a short introduction on the pharmacology of GHB/GBL, followed by a summary of the epidemiology of GHB abuse, an overview of GHB dependence syndrome and GHB/GBL withdrawal syndrome is provided. Finally, the existing literature on management of GHB detoxification, both planned and unplanned, as well as the available management of GHB withdrawal syndrome, is summarized. Although no systematic studies on detoxification and management of withdrawal have been performed to date, general recommendations are given on pharmacological treatment and preferred treatment setting.

The Neurobiological Mechanisms of Gamma-Hydroxybutyrate Dependence and Withdrawal and Their Clinical Relevance: A Review

OBJECTIVE

x03B3;-Hydroxybutyrate (GHB) has gained popularity as a drug of abuse. In the Netherlands the number of patients in treatment for GHB dependence has increased sharply. Clinical presentation of GHB withdrawal can be life threatening. We aim, through this overview, to explore the neurobiological pathways causing GHB dependency and withdrawal, and their implications for treatment choices.

METHODS

In this work we review the literature discussing the findings from animal models to clinical studies focused on the neurobiological pathways of endogenous but mainly exogenous GHB.

RESULTS

Chronic abuse of GHB exerts multifarious neurotransmitter and neuromodulator effects on x03B3;-aminobutyric acid (GABA), glutamate, dopamine, serotonin, norepinephrine and cholinergic systems. Moreover, important effects on neurosteroidogenesis and oxytocin release are wielded. GHB acts mainly via a bidirectional effect on GABAB receptors (GABABR; subunits GABAB1 and GABAB2), depending on the subunit of the GIRK (G-protein-dependent ion inwardly rectifying potassium) channel involved, and an indirect effect of the cortical and limbic inputs outside the nucleus accumbens. GHB also activates a specific GHB receptor and β1-subunits of α4-GABAAR. Reversing this complex interaction of neurobiological mechanisms by the abrupt cessation of GHB use results in a withdrawal syndrome with a diversity of symptoms of different intensity, depending on the pattern of GHB abuse.

CONCLUSION

The GHB withdrawal symptoms cannot be related to a single mechanism or neurological pathway, which implies that different medication combinations are needed for treatment. A single drug class, such as benzodiazepines, gabapentin or antipsychotics, is unlikely to be sufficient to avoid life-threatening complications. Detoxification by means of titration and tapering of pharmaceutical GHB can be considered as a promising treatment that could make polypharmacy redundant.

A pharmacokinetic evaluation and metabolite identification of the GHB receptor antagonist NCS-382 in mouse informs novel therapeutic strategies for the treatment of GHB intoxication

Gamma‐aminobutyric acid (GABA) is an endogenous inhibitory neurotransmitter and precursor of gamma‐hydroxybutyric acid (GHB). NCS‐382 (6,7,8,9‐tetrahydro‐5‐hydroxy‐5H‐benzo‐cyclohept‐6‐ylideneacetic acid), a known GHB receptor antagonist, has shown significant efficacy in a murine model of succinic semialdehyde dehydrogenase deficiency (SSADHD), a heritable neurological disorder featuring chronic elevation of GHB that blocks the final step of GABA degradation. NCS‐382 exposures and elimination pathways remain unknown; therefore, the goal of the present work was to obtain in vivo pharmacokinetic data in a murine model and to identify the NCS‐382 metabolites formed by mouse and human. NCS‐382 single‐dose mouse pharmacokinetics were established following an intraperitoneal injection (100, 300, and 500 mg/kg body weight) and metabolite identification was conducted using HPLC‐MS/MS. Kinetic enzyme assays employed mouse and human liver microsomes. Upon gaining an understanding of the NCS‐382 clearance mechanisms, a chemical inhibitor was used to increase NCS‐382 brain exposure in a pharmacokinetic/pharmacodynamic study. Two major metabolic pathways of NCS‐382 were identified as dehydrogenation and glucuronidation. The K_m for the dehydrogenation pathway was determined in mouse (K_m = 29.5 ± 10.0 μmol/L) and human (K_m = 12.7 ± 4.8 μmol/L) liver microsomes. Comparable parameters for glucuronidation were >100 μmol/L in both species. Inhibition of NCS‐382 glucuronidation, in vivo, by diclofenac resulted in increased NCS‐382 brain concentrations and protective effects in gamma‐butyrolactone‐treated mice. These initial evaluations of NCS‐382 pharmacokinetics and metabolism inform the development of NCS‐382 as a potential therapy for conditions of GHB elevation (including acute intoxication & SSADHD).

Presentations to an urban emergency department in Switzerland due to acute γ-hydroxybutyrate toxicity

Background

γ-Hydroxybutyrate (GHB) is a drug of abuse with dose-dependent sedative effects. Systematic data on the acute toxicity of GHB from emergency department (ED) presentations over a long period of time are currently missing from the literature. The present study described the clinical features of GHB toxicity.

Methods

Retrospective case series of GHB intoxications seen in an urban ED.

Results

From January 2002 to September 2015, 78 GHB-related intoxication cases were recorded (71 % male patients). The mean ± SD age was 29 ± 8 years. The co-use of alcohol and/or other illicit drugs was reported in 65 % of the cases. Neurological symptoms other than central nervous system depression included agitation (40 %) and clonus (21 %). The most frequent reasons for admission were coma (64 %) and agitation (23 %). The median time to regain consciousness was 90 min (range, 3–400 min). Sudden recovery was reported in 25 cases (32 %). Coma was not significantly associated with polyintoxication. Coma occurred in 77 % of the alcohol co-users and in 62 % ofthe non-alcohol users (p=0.052). The mean recovery time in comatose patients was 142 min in patients with co-use of alcohol compared with 89 min in patients without alcohol co-use (p=0.07). Alcohol co-use was not significantly associated with nausea/vomiting (p=0.07). The co-use of stimulants was not significantly associated with non-responsive coma (Glasgow Coma Scale = 3) or mean recovery time. Analytical confirmation of GHB was available in 37 cases (47 %), with additional quantitative analysis in 20 cases. The median GHB concentration was 240 mg/L (range, 8.3–373 mg/L). Intoxication was severe in 72 % of the cases. No fatalities occurred, and 72 % of the patients were discharged directly home from the ED.

Discussion

There were trend associations between alcohol co-use and frequency and length of coma and nausea/vomiting which did not reach the significance level (all p=0.05-0.07) but may nevertheless be clinically relevant. As the exact time of use is not always known, and co-use of other substances can affect the severity of poisoning, no definitive conclusions can be drawn regarding the association between GHB concentration and severity.

Conclusion

Impaired consciousness and agitation were typical findings of GHB intoxication. The co-use of alcohol and/or other illicit substances is common but was not significantly associated with the severity of the intoxications in our study.

GHB pharmacology and toxicology: acute intoxication, concentrations in blood and urine in forensic cases and treatment of the withdrawal syndrome

The illicit recreational drug of abuse, γ-hydroxybutyrate (GHB) is a potent central nervous system depressant and is often encountered during forensic investigations of living and deceased persons. The sodium salt of GHB is registered as a therapeutic agent (Xyrem®), approved in some countries for the treatment of narcolepsy-associated cataplexy and (Alcover®) is an adjuvant medication for detoxification and withdrawal in alcoholics. Trace amounts of GHB are produced endogenously (0.5-1.0 mg/L) in various tissues, including the brain, where it functions as both a precursor and a metabolite of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA). Available information indicates that GHB serves as a neurotransmitter or neuromodulator in the GABAergic system, especially via binding to the GABA-B receptor subtype. Although GHB is listed as a controlled substance in many countries abuse still continues, owing to the availability of precursor drugs, γ-butyrolactone (GBL) and 1,4-butanediol (BD), which are not regulated. After ingestion both GBL and BD are rapidly converted into GHB (t½ ~1 min). The Cmax occurs after 20-40 min and GHB is then eliminated from plasma with a half-life of 30-50 min. Only about 1-5% of the dose of GHB is recoverable in urine and the window of detection is relatively short (3-10 h). This calls for expeditious sampling when evidence of drug use and/or abuse is required in forensic casework. The recreational dose of GHB is not easy to estimate and a concentration in plasma of ~100 mg/L produces euphoria and disinhibition, whereas 500 mg/L might cause death from cardiorespiratory depression. Effective antidotes to reverse the sedative and intoxicating effects of GHB do not exist. The poisoned patients require supportive care, vital signs should be monitored and the airways kept clear in case of emesis. After prolonged regular use of GHB tolerance and dependence develop and abrupt cessation of drug use leads to unpleasant withdrawal symptoms. There is no evidence-based protocol available to deal with GHB withdrawal, apart from administering benzodiazepines.

Withdrawal from gamma-hydroxybutyrate, 1,4-butanediol and gamma-butyrolactone: a case report and systematic review

1,4-Butanediol (1,4-BD) is an industrial solvent that is metabolized to gamma-hydroxybutyrate (GHB), a gamma-aminobutyric acid agonist and central nervous system depressant. GHB and its analogues are popular drugs of abuse. Withdrawal from these agents is characterized by autonomic instability and altered mental status. We report a case of withdrawal from 1,4-BD lasting 6 days and complicated by new onset of seizures and rhabdomyolysis. In addition, we conducted a systematic review of the English literature pertaining to withdrawal from GHB, 1,4-BD and gamma-butyrolactone (GBL). Data collected from source articles included last use prior to symptom onset, clinical features on presentation, duration of symptoms and outcome. Twenty-seven studies with 57 episodes of withdrawal were included. Thirty-six cases (63%) involved GHB, 3 cases (5%) involved 1,4-BD and 18 (32%) involved GBL. The most common patient symptoms were tremor (67%), hallucinations (63%), tachycardia (63%) and insomnia (58%). Seizures and rhabdomyolysis each occurred in 7% of cases, but only 1 death occurred. Emergency physicians must consider withdrawal from these agents when patients present with clinical features suggestive of a sedative-hypnotic withdrawal syndrome.

A Novel Monocarboxylate Transporter Inhibitor as a Potential Treatment Strategy for γ-Hydroxybutyric Acid Overdose

PURPOSE

Monocarboxylate transporter (MCT) inhibition represents a potential treatment strategy for γ-hydroxybutyric acid (GHB) overdose by blocking its renal reabsorption in the kidney. This study further evaluated the effects of a novel, highly potent MCT inhibitor, AR-C155858, on GHB toxicokinetics/toxicodynamics (TK/TD).

METHODS

Rats were administered GHB (200, 600 or 1500 mg/kg i.v. or 1500 mg/kg po) with and without AR-C155858. Breathing frequency was continuously monitored using whole-body plethysmography. Plasma and urine samples were collected up to 8 h. The effect of AR-C155858 on GHB brain/plasma partitioning was also assessed.

RESULTS

AR-C155858 treatment significantly increased GHB renal and total clearance after intravenous GHB administration at all the GHB doses used in this study. GHB-induced respiratory depression was significantly improved by AR-C155858 as demonstrated by an improvement in the respiratory rate. AR-C155858 treatment also resulted in a significant reduction in brain/plasma partitioning of GHB (0.1 ± 0.03) when compared to GHB alone (0.25 ± 0.02). GHB CLR and CLoral (CL/F) following oral administration were also significantly increased following AR-C155858 treatment (from 1.82 ± 0.63 to 5.74 ± 0.86 and 6.52 ± 0.88 to 10.2 ± 0.75 ml/min/kg, respectively).

CONCLUSION

The novel and highly potent MCT inhibitor represents a potential treatment option for GHB overdose.

Risk assessment of GBL as a substitute for the illicit drug GHB in the Netherlands. A comparison of the risks of GBL versus GHB

In the Netherlands, γ-hydroxybutyric acid (GHB) was recently banned, but γ-butyrolactone (GBL) was not. As such, GBL remained a legal alternative to GHB. This review compares the risks of GBL and GHB. Pure GBL is per unit of volume about threefold stronger and therefore threefold more potent than currently used GHB-preparations in the Netherlands. Like GHB, GBL use hardly leads to organ toxicity, although, as with GHB, frequent GBL use may lead to repeated comas that may result in residual impairments in cognitive function and memory. Little is known about the prevalence of GBL use in Europe, but the recent increase in improper trading in GBL confirms that users of GHB gradually switch to the use of GBL. This shift may result in an increase in the number GBL dependent users, because the dependence potential of GBL is as great as that of GHB. Severe withdrawal symptoms and a high relapse rate are seen following cessation of heavy GBL use. GBL-dependent users seem to be severe (dependent, problematic) GHB users who started using GBL, the legal GHB substitute. Subjects who are solely dependent to GBL are rarely reported. About 5-10% of the treatment seeking GHB dependent subjects also use GBL and this subpopulation forms a vulnerable group with multiple problems. Fatal accidents with GBL are rarely reported, but non-fatal GHB (or GBL) overdoses frequently occur for which supportive treatment is needed. It is recommended to monitor the recreational use of GBL, the rate of GBL dependence treatment, and the improper trading of GBL.

GHB acid: A rage or reprive

Gamma-hydroxybutyric acid (GHB) is a naturally occurring analog of gamma-aminobutyric acid (GABA) that has been used in research and clinical medicine for many years. GHB was used clinically as an anesthetic in the 1960s but was withdrawn due to side effects that included seizures and coma. GHB has been implicated in a number of crime types; most notably in drug-facilitated sexual assault. GHB is abused by three main groups of users: Body builders who use the substance believing that it stimulated the release of growth hormone; sexual predators who covertly administer the drug for its sedative and amnesic effects and club-goers (rave parties) who take the drug for its euphoric effects. The short-lived hypnotic effects, relative safety and widespread availability of the drug have made it particularly well suited to this role. The drug has an addictive potential if used for long term. The primary effects of GHB use are those of a CNS depressant and therefore range from relaxation, to euphoria, confusion, amnesia, hallucinations, and coma. Despite the increased regulation, GHB remains widely available through the Internet where one can easily purchase the necessary reagents as well as recipes for home production. There are reports of patients being unresponsive to painful stimuli and cases of oral self-mutilations linked to the abuse of GHB, though quiet rare. Such cases should remind odontologists that intra-oral lesions may be the result of self-mutilation either due to mental illness or altered states caused by the use of prescription or non-prescription drugs.

GHB acid: A rage or reprive

Gamma-hydroxybutyric acid (GHB) is a naturally occurring analog of gamma-aminobutyric acid (GABA) that has been used in research and clinical medicine for many years. GHB was used clinically as an anesthetic in the 1960s but was withdrawn due to side effects that included seizures and coma. GHB has been implicated in a number of crime types; most notably in drug-facilitated sexual assault. GHB is abused by three main groups of users: Body builders who use the substance believing that it stimulated the release of growth hormone; sexual predators who covertly administer the drug for its sedative and amnesic effects and club-goers (rave parties) who take the drug for its euphoric effects. The short-lived hypnotic effects, relative safety and widespread availability of the drug have made it particularly well suited to this role. The drug has an addictive potential if used for long term. The primary effects of GHB use are those of a CNS depressant and therefore range from relaxation, to euphoria, confusion, amnesia, hallucinations, and coma. Despite the increased regulation, GHB remains widely available through the Internet where one can easily purchase the necessary reagents as well as recipes for home production. There are reports of patients being unresponsive to painful stimuli and cases of oral self-mutilations linked to the abuse of GHB, though quiet rare. Such cases should remind odontologists that intra-oral lesions may be the result of self-mutilation either due to mental illness or altered states caused by the use of prescription or non-prescription drugs.

Sociodemographic and substance use characteristics of γ hydroxybutyrate (GHB) dependent inpatients and associations with dependence severity

BACKGROUND

The number of admissions to addiction treatment centers in the Netherlands for gamma hydroxybutyrate (GHB) dependence is rapidly growing. Until now, treatment seeking GHB users have hardly been studied. This study characterizes inpatients in treatment for GHB dependence in terms of sociodemographics, motives for substance use and reasons for seeking treatment. In addition, variables associated with dependence severity are identified.

METHODS

Patients were recruited by their therapists at 4 different addiction treatment centers dispersed throughout the Netherlands. They were asked to fill out the questionnaire, including sociodemographic and clinical characteristics, GHB and other drug use, and a modified version of the Drug Use Disorders Identification Test (DUDIT) to screen for GHB dependence. The associations of relevant variables with dependence severity were determined using multiple regression analysis.

RESULTS

A total of 75 inpatients (response rate 90.4%) participated in the study. Most patients were young (mean 26.8 ± 9.1) males (73%) with low education (78%) and not employed (48%). Most of them (75%) had started using GHB the year before treatment admission, 42 (56%) frequently combined GHB with sedatives and 26 (35%) frequently combined GHB with stimulants. Dependence severity was strongly associated with sleep problems and the combined use of GHB and stimulants.

CONCLUSION

This study shows that sociodemographic characteristics of GHB inpatients are similar to those of problematic users of other club drugs. Sleep problems and combined use of GHB and stimulants were strongly associated with GHB dependence. Together, these factors might help to better identify people at risk for GHB dependence.

Therapeutic efficacy of magnesium valproate in succinic semialdehyde dehydrogenase deficiency

Succinic semialdehyde dehydrogenase deficiency (SSADHD), a disorder of γ-aminobutyric acid (GABA) metabolism, manifests typically as a nonprogressive neurodevelopmental disorder with cognitive deficiency, neuropsychiatric morbidity and epilepsy. Therapy targets symptomatic seizures and neurobehavioral disturbances. We report an adolescent female with SSADHD whose unresponsiveness to a broad spectrum of antiepileptics was circumvented with magnesium valproate (MgVPA). Epilepsy remains well controlled in our patient, with concomitant improvements in behavioral symptoms and an absence of adverse symptoms. MgVPA intervention may have utility in SSADHD.

Teenage toxins: recreational poisoning in the adolescent

Adolescents are experimenting with recreational drugs on a regular basis, particularly at social gatherings such as parties, raves and mass events. A combination of reduced fluid intake, physical activity and drug-induced hyperthermia leads to complications such as heat stroke, delirium and potentially death. The clinician needs to be aware of the variety of pharmacologically active substances available in the recreational marketplace in order to diagnose and manage these patients. Recreational misadventure, because of incorrect dosage or mixing multiple substances, is a common reason for teenagers presenting to hospital with toxidromes. Death from club drug overdose is more likely to be associated with suicidal intent, related risky behaviour and trauma, as well as the inherent toxicity of the drug itself. Although many teenagers are concerned about 'drink spiking' with club drugs, the most common agent causing drink spiking incidents is ethanol.

Substitution therapy for alcoholism: time for a reappraisal?

A number of compounds already in use as medications for various indications substitute for ethanol at clinically relevant brain pathways, in particular, at gamma-aminobutyric acid (GABA) receptors. Nevertheless, although substitute medications have been recognized for heroin and tobacco dependence, patients with alcohol dependence are rarely offered an analogous approach. Benzodiazepines may have paradoxical effects, and abuse and dependence are known. Baclofen (GABA(B) agonist) has not been associated with dependence or misuse and has been effective in several trials in preventing relapse, although research is required to establish the optimal dosing regimen. GABA-ergic anticonvulsants, helpful in treating withdrawal, have yet to emerge as effective in relapse prevention. Clomethiazole and sodium oxybate, the latter having been shown to be effective in relapse prevention, have incurred a reputation for dependence and abuse. However, data have emerged showing that the risk of abuse of sodium oxybate is lower than many clinicians had foreseen. For a condition where existing therapies are only effective in a proportion of patients, and which has high morbidity and mortality, the time now seems right for reappraising the use of substitute prescribing for alcohol dependence.

Analysis of electrical brain waves in neurotoxicology: γ-hydroxybutyrate

Advances in computer technology have allowed quantification of the electroencephalogram (EEG) and expansion of quantitative EEG (qEEG) analysis in neurophysiology, as well as clinical neurology, with great success. Among the variety of techniques in this field, frequency (spectral) analysis using Fast Fourier Transforms (FFT) provides a sensitive tool for time-course studies of different compounds acting on particular neurotransmitter systems. Studies presented here include Electrocorticogram (ECoG) analysis following exposure to a glutamic acid analogue - domoic acid (DOM), psychoactive indole alkaloid - ibogaine, as well as cocaine and gamma-hydroxybutyrate (GHB). The ECoG was recorded in conscious rats via a tether and swivel system. The EEG signal frequency analysis revealed an association between slow-wave EEG activity delta and theta and the type of behavioral seizures following DOM administration. Analyses of power spectra obtained in rats exposed to cocaine alone or after pretreatment with ibogaine indicated the contribution of the serotonergic system in ibogaine mediated response to cocaine (increased power in alpha(1) band). Ibogaine also lowered the threshold for cocaine-induced electrographic seizures (increased power in the low-frequency bands, delta and theta). Daily intraperitoneal administration of cocaine for two weeks was associated with a reduction in slow-wave ECoG activity 24 hrs following the last injection when compared with controls. Similar decreased cortical activity in low-frequency bands observed in chronic cocaine users has been associated with reduced metabolic activity in the frontal cortex. The FFT analyses of power spectra relative to baseline indicated a significant energy increase over all except beta(2) frequency bands following exposure to 400 and 800 mg/kg GHB. The EEG alterations detected in rats following exposure to GHB resemble absence seizures observed in human petit mal epilepsy. Spectral analysis of the EEG signals combined with behavioral observations may prove to be a useful approach in studying chronic exposure to drugs of abuse and treatment of drug dependence.

Succinic semialdehyde dehydrogenase: biochemical-molecular-clinical disease mechanisms, redox regulation, and functional significance

Succinic semialdehyde dehydrogenase (SSADH; aldehyde dehydrogenase 5a1, ALDH5A1; E.C. 1.2.1.24; OMIM 610045, 271980) deficiency is a rare heritable disorder that disrupts the metabolism of the inhibitory neurotransmitter 4-aminobutyric acid (GABA). Identified in conjunction with increased urinary excretion of the GABA analog gamma-hydroxybutyric acid (GHB), numerous patients have been identified worldwide and the autosomal-recessive disorder has been modeled in mice. The phenotype is one of nonprogressive neurological dysfunction in which seizures may be prominently displayed. The murine model is a reasonable phenocopy of the human disorder, yet the severity of the seizure disorder in the mouse exceeds that observed in SSADH-deficient patients. Abnormalities in GABAergic and GHBergic neurotransmission, documented in patients and mice, form a component of disease pathophysiology, although numerous other disturbances (metabolite accumulations, myelin abnormalities, oxidant stress, neurosteroid depletion, altered bioenergetics, etc.) are also likely to be involved in developing the disease phenotype. Most recently, the demonstration of a redox control system in the SSADH protein active site has provided new insights into the regulation of SSADH by the cellular oxidation/reduction potential. The current review summarizes some 30 years of research on this protein and disease, addressing pathological mechanisms in human and mouse at the protein, metabolic, molecular, and whole-animal level.

4-Hydroxybutyric aciduria associated with catheter usage: a diagnostic pitfall in the identification of SSADH deficiency

Succinic semialdehyde dehydrogenase deficiency is a slowly progressive to static neurological disorder featuring elevated concentrations of 4-hydroxybutyric acid in body fluids. We present two patients with elevated 4-hydroxybutyric acid in urine which was later shown to be linked to catheter usage.

A case of γ-butyrolactone associated with severe withdrawal delirium and acute renal failure

γ-Butyrolactone (GBL) is a popular drug of abuse which is easily available over the internet. Following a UK classification change to a class C drug in January 2010, internet supply has become difficult. Some of the effects have resulted in sourcing GBL from industrial solvents. We report a case of a 24-year-old man who was admitted for detoxification from GBL. He reported having sourced the GBL by diluting the contents of nail varnish remover pads with water. During his admission he developed a severe withdrawal delirium and acute renal failure. He required admission to the intensive care unit. Physicians and psychiatrists should be aware of toxic sources of GBL leading to renal failure and consider GBL in those presenting with agitation, psychosis or coma.

[Withdrawal syndrome after abuse of GHB (Gamma-Hydroxybutyrate) and its physiological precursors - its relevance for child and adolescent psychiatrists]

BACKGROUND

The chronic abuse of Gamma-Hydroxybutyrate (GHB) as a designer drug as well as it's physiological precursors Gamma-Butyrolactone (GBL) and 1,4-Butandiole (1,4-BD) confronts child and adolescent psychiatrists with new challenges. The acute withdrawal of GHB with its cardiovascular and delirant symptoms is of particular importance for child and adolescent psychiatrists.

METHODS

In the present paper theoretical and biological aspects of acute GHB-/GBL-/1,4-BD-withdrawal syndrome are presented, and selected cases are discussed as regards potential treatment.

RESULTS

High dose treatment with benzodiazepines was successful in some cases of acute GHB-/GBL-/1,4-BD-withdrawal syndrome. Complications were severe dystonia under neuroleptic treatment, and also side-effects of treatment with benzodiazepines. Further problems were vegetative symptoms, electrocardiographic changes, rhabdomyolysis, acute renal failure, and death.

CONCLUSION

Acute GHB-withdrawal syndrome is a life-threatening condition which requires immediate intensive care treatment along with continuous monitoring of vital parameters. As acute GHB-withdrawal syndrome can present with symptoms close to psychotic episodes or acute alcohol withdrawal this condition is relevant for child and adolescent psychiatrists.

Catabolism of 4-hydroxyacids and 4-hydroxynonenal via 4-hydroxy-4-phosphoacyl-CoAs

4-Hydroxyacids are products of ubiquitously occurring lipid peroxidation (C(9), C(6)) or drugs of abuse (C(4), C(5)). We investigated the catabolism of these compounds using a combination of metabolomics and mass isotopomer analysis. Livers were perfused with various concentrations of unlabeled and labeled saturated 4-hydroxyacids (C(4) to C(11)) or 4-hydroxynonenal. All the compounds tested form a new class of acyl-CoA esters, 4-hydroxy-4-phosphoacyl-CoAs, characterized by liquid chromatography-tandem mass spectrometry, accurate mass spectrometry, and (31)P-NMR. All 4-hydroxyacids with five or more carbons are metabolized by two new pathways. The first and major pathway, which involves 4-hydroxy-4-phosphoacyl-CoAs, leads in six steps to the isomerization of 4-hydroxyacyl-CoA to 3-hydroxyacyl-CoAs. The latter are intermediates of physiological beta-oxidation. The second and minor pathway involves a sequence of beta-oxidation, alpha-oxidation, and beta-oxidation steps. In mice deficient in succinic semialdehyde dehydrogenase, high plasma concentrations of 4-hydroxybutyrate result in high concentrations of 4-hydroxy-4-phospho-butyryl-CoA in brain and liver. The high concentration of 4-hydroxy-4-phospho-butyryl-CoA may be related to the cerebral dysfunction of subjects ingesting 4-hydroxybutyrate and to the mental retardation of patients with 4-hydroxybutyric aciduria. Our data illustrate the potential of the combination of metabolomics and mass isotopomer analysis for pathway discovery.

Narcolepsy and depression and the neurobiology of gammahydroxybutyrate

A voluminous literature describes the relationship between disturbed sleep and depression. The breakdown of sleep is one of the cardinal features of depression and often also heralds its onset. Frequent arousals, periods of wakefulness and a short sleep onset REM latency are typical polysomnographic features of depression. The short latency to REM sleep has been attributed to the combination of a monoaminergic deficiency and cholinergic supersensitivity and these irregularities have been proposed to form the biological basis of the disorder. A similar imbalance between monoaminergic and cholinergic neurotransmission has been found in narcolepsy, a condition in which frequent awakenings, periods of wakefulness and short sleep onset REM latencies are also characteristic findings during sleep. In many cases of narcolepsy, this imbalance appears to result from a deficiency of hypocretin but once established, whether in depression or narcolepsy, this disequilibrium sets the stage for the dissociation or premature appearance of REM sleep and for the dissociation of the motor inhibitory component of REM sleep or cataplexy. In the presence of this monoaminergic/cholinergic imbalance, gammahydroxybutyrate (GHB) may acutely further reduce the latency of REM sleep and induce cataplexy, in both patients with narcolepsy or depression. On the other hand, the repeated nocturnal application of GHB in patients with narcolepsy improves the continuity of sleep, prolongs the latency to REM sleep and prevents cataplexy. Evidence to date suggests that GHB may restore the normal balance between monoaminergic and cholinergic neurotransmission. As such, the repeated use of GHB at night and the stabilization of sleep over time makes GHB an effective treatment for narcolepsy and a potentially effective treatment for depression.

Gamma-hydroxybutyrate withdrawal syndrome: dangerous but not well-known

Gamma-hydroxybutyrate (GHB) is an endogenous inhibitory neurotransmitter and anesthetic agent that is being abused as a 'club drug.' Withdrawal symptoms after cessation of GHB use are common and depend on the intensity of use. However, GHB withdrawal syndrome and delirium are unfamiliar to most psychiatrists, probably due to the fact that neither textbooks nor guidelines cover the subject. The GHB withdrawal syndrome may have a fulminant course that progresses to delirium. In those severe cases, admission to a general hospital and involvement of a psychiatrist become necessary. We present two cases of severe GHB withdrawal delirium, provide an overview of the literature and conclude with treatment recommendations.

Gamma-butyrolactone (GBL) disruption of passive avoidance learning in the day-old chick appears to be due to its effect on GABAB not gamma-hydroxybutyric [corrected] acid (GHB) receptors

Gamma-butyrolactone (GBL) is a prodrug to gamma-hydroxybutyric acid (GHB) and metabolises to GHB when ingested. Discrimination stimulus studies report generalisation of effects of GHB to GBL. While amnesia is one of the most commonly reported symptoms of GHB's ingestion in human users, as yet few studies have examined this effect. Although an endogenous GHB specific receptor is present in the brain, several studies have indicated that the clinical effects of exogenous doses of GBL/GHB are due to its action on GABA(B) receptors rather than on the GHB receptor. In this series of studies, New Hampshire x White leghorn cockerels were trained using a modified version of the passive avoidance learning task. Subcutaneous injections of GBL induced a memory deficit by 10 min post-training, which persisted for at least 24 h. No effect on memory was seen with administration of the specific GHB agonist NCS-356 (gamma-p-chlorophenyl-trans-4-hydroxycrotonate). The GBL-induced memory deficit appeared similar to the deficit produced by baclofen, where the antagonist facilitated learning. Additionally, GBL-induced memory deficit was ameliorated by application of a GABA(B) antagonist. The results support the hypothesis that GBL exerts its influence on memory via the GABA(B) receptor rather than by the specific GHB receptor.

The distribution of gamma-hydroxybutyrate-induced Fos expression in rat brain: comparison with baclofen

gamma-Hydroxybutyrate (GHB) is a euphoric, prosocial and sleep inducing drug that binds with high affinity to its own GHB receptor site and also more weakly to GABA(B) receptors. GHB is efficacious in the treatment of narcolepsy and alcoholism, but heavy use can lead to dependence and withdrawal. Many effects of GHB (sedation, hypothermia, catalepsy) are mimicked by GABA(B) receptor agonists (e.g. baclofen). However other effects (euphoric and prosocial effects and a therapeutic effect in narcolepsy) are not. The present study used Fos immunohistochemistry to assess the neural activation produced in rat brain by medium to high doses of GHB (250, 500 and 1000 mg/kg) and a high dose of baclofen (10 mg/kg) that produced similar sedation to 500 mg/kg GHB. Results showed many common regions of activation with these two drugs including the supraoptic, paraventricular, median preoptic and ventral premammillary nuclei of the hypothalamus, the central nucleus of the amygdala, Edinger-Westphal nucleus, lateral parabrachial nucleus, locus coeruleus, and nucleus of the solitary tract. GHB (500 mg/kg), but not baclofen (10 mg/kg), induced significant Fos expression in the median raphe nucleus and lateral habenula, while a higher dose of GHB (1000 mg/kg) induced additional Fos expression in the islands of Calleja, dentate gyrus (polymorphic layer) and arcuate nucleus, and in various regions implicated in rapid and non-rapid eye movement sleep (laterodorsal tegmental nucleus, tuberomammillary nucleus and the ventrolateral and anterodorsal preoptic nuclei). Surprisingly, Fos immunoreactivity was not observed with either GHB or baclofen in reward-relevant regions such as the nucleus accumbens, striatum and ventral tegmental area. Overall these results indicate a distinctive signature of brain activation with GHB that may be only partly due to GABA(B) receptor effects. This confirms a unique neuropharmacological profile for GHB and indicates key neural substrates that may underlie its characteristic influence on sleep, body temperature, sociability and endocrine function.