Regional Fos-expression induced by γ-hydroxybutyrate (GHB): Comparison with γ-butyrolactone (GBL) and effects of co-administration of the GABAB antagonist SCH 50911 and putative GHB antagonist NCS-382

Cognitive Impairment Following Clinical or Recreational Use of Gammahydroxybutyric Acid (GHB): A Systematic Review

BACKGROUND

GHB (gamma-hydroxybutyric acid; sodium oxybate) is a general anaesthetic that is clinically used for the treatment of narcolepsy, cataplexy, alcohol withdrawal and alcohol relapse prevention. In addition, GHB is recreationally used. Most clinical and recreational users regard GHB as an innocent drug devoid of adverse effects, despite its high dependence potential and possible neurotoxic effects. At high doses, GHB may lead to a comatose state. This paper systematically reviews possible cognitive impairments due to clinical and recreational GHB use.

METHODS

PubMed and PsychINFO were searched for literature data about the acute and residual cognitive deficits following GHB use. This review is conducted using the PRISMA protocol.

RESULTS

A total of 43 reports covering human and animal data on GHB-induced cognitive impairments were eligible and reviewed. This systematic review found no indication for cognitive impairments after clinical GHB use. However, it supports the view that moderate GHB use may result in acute short-term cognitive impairments, whereas regular high-dose GHB use and/or multiple GHB-induced comas are probably neurotoxic resulting in long-term residual cognitive impairments.

CONCLUSION

These results emphasize the need for awareness among clinicians and recreational users to minimize negative health consequences of recreational GHB use, particularly when high doses are used and GHB-induced comas occur.

At the heart of the interoception network: Influence of the parasubthalamic nucleus on autonomic functions and motivated behaviors

The parasubthalamic nucleus (PSTN), a small nucleus located on the lateral edge of the posterior hypothalamus, has emerged in recent years as a highly interconnected node within the network of brain regions sensing and regulating autonomic function and homeostatic needs. Furthermore, the strong integration of the PSTN with extended amygdala circuits makes it ideally positioned to serve as an interface between interoception and emotions. While PSTN neurons are mostly glutamatergic, some of them also express neuropeptides that have been associated with stress-related affective and motivational dysfunction, including substance P, corticotropin-releasing factor, and pituitary adenylate-cyclase activating polypeptide. PSTN neurons respond to food ingestion and anorectic signals, as well as to arousing and distressing stimuli. Functional manipulation of defined pathways demonstrated that the PSTN serves as a central hub in multiple physiologically relevant networks and is notably implicated in appetite suppression, conditioned taste aversion, place avoidance, impulsive action, and fear-induced thermoregulation. We also discuss the putative role of the PSTN in interoceptive dysfunction and negative urgency. This review aims to synthesize the burgeoning preclinical literature dedicated to the PSTN and to stimulate interest in further investigating its influence on physiology and behavior.

Successful Treatment of Severe Gamma-Hydroxybutyric Acid Withdrawal Syndrome With Dantrolene

The prevalence of gamma-butyrolactone/gamma-hydroxybutyric acid (GBL/GHB) use is increasing. The gravity and number of incidents with this drug are relatively high. A feared complication is addiction and its withdrawal syndrome, which can be life-threatening and is difficult to treat. We present the case of a 31-year-old man, admitted to the ICU because of accidental GBL withdrawal. The patient was tachycardic, sweaty, extremely agitated, and showed signs of psychosis. High doses of benzodiazepines, propofol, sufentanil, and quetiapine could not sedate the patient sufficiently. Dosing with pharmaceutical GHB was challenging due to severe gastric retention. As the patient developed hyperthermia and rhabdomyolysis, signs of a neuroleptic malignant syndrome (NMS), he was treated with dantrolene. After 14 days, the patient was discharged to a psychiatric clinic for further treatment. GHB affects multiple neurotransmitters and chronic use causes the up- or down-regulation of several receptors. During GHB withdrawal, the patient developed a hyperexcitable state, in which there was insufficient gamma-aminobutyric acid (GABA) (the most important inhibiting neurotransmitter) and an abundance of glutamate (the most important excitatory neurotransmitter). High-dose benzodiazepines are often advocated as the first-line treatment, but benzodiazepine resistance has frequently been reported. Therefore, treatment with pharmaceutical GHB is advised. Patients with GHB-withdrawal who have clinical signs of NMS can be treated with dantrolene because it regulates the distorted calcium secretion and affects the serotonin and cholinergic system.

Regional c-Fos expression induced by peripheral oxytocin administration is prevented by the vasopressin 1A receptor antagonist SR49059

Peripherally administered oxytocin induces a wide range of behavioural and physiological effects that are thought to be mediated by the oxytocin receptor (OTR). However, oxytocin also has considerable affinity for the vasopressin 1A receptor (V_1AR), such that various oxytocinergic effects may in fact be mediated by the V_1AR rather than the OTR. Here we used c-Fos immunohistochemistry to determine the extent to which the regional pattern of neuronal activation produced by peripheral oxytocin involves the V_1AR. Male Wistar rats were administered oxytocin (1mg/kg, IP) alone, or following pre-treatment with the V_1AR antagonist SR49059 (1mg/kg, IP), and were assessed for locomotor activity changes and for c-Fos expression across a number of brain regions. Oxytocin reduced the distance travelled by rats during a 70min test session, and this inhibitory behavioural effect was prevented by SR49059. Consistent with previous reports, oxytocin increased c-Fos expression in a number of brain regions. In several of these regions-the supraoptic and paraventricular (PVN) nuclei of the hypothalamus, locus coeruleus and nucleus of the solitary tract-the c-Fos response was prevented by SR49059 pre-treatment. Notably, SR49059 inhibited the c-Fos activation in oxytocin-synthesising magnocellular neurons in the PVN. However, c-Fos expression in the central amygdala to oxytocin was unaffected by SR49059. The current findings add to an increasing body of research suggesting that many of the functional effects of oxytocin may be V_1AR mediated.

Contrasting regional Fos expression in adolescent and young adult rats following acute administration of the antidepressant paroxetine

Adolescents and adults may respond differently to antidepressants, with poorer efficacy and greater probability of adverse effects in adolescents. The mechanisms underlying this differential response are largely unknown, but likely relate to an interaction between the neural effects of antidepressants and brain development. We used Fos immunohistochemistry to examine regional differences in adolescent (postnatal day (PND) 28) and young adult (PND 56) male, Wistar rats given a single injection of the selective serotonin reuptake inhibitor paroxetine (10mg/kg). Paroxetine induced widespread Fos expression in both adolescent and young adult rats. Commonly affected areas include the bed nucleus of the stria terminalis (dorsolateral), medial preoptic area, paraventricular hypothalamic and thalamic nuclei and central nucleus of the amygdala. Fos expression was generally lower in adolescents with significantly greater Fos expression observed in young adults in the prelimbic cortex, supraoptic nucleus, basolateral amygdala, lateral parabrachial and Kölliker-Fuse nuclei. However, a small subset of regions showed greater adolescent Fos expression including the nucleus accumbens shell, lateral habenula and dorsal raphe. Paroxetine increased plasma corticosterone concentrations in young adults, but not adolescents. Plasma paroxetine levels were not significantly different between the age groups. These results indicate a different c-Fos signature of acute paroxetine in adolescent rats, with greater activation in key mesolimbic and serotonergic regions, but a more subdued cortical, brainstem and hypothalamic response. This suggests that the atypical response of adolescents to paroxetine may be related to a blunted neuroendocrine response, combined with insufficient top-down regulation of limbic regions involved in reward and impulsivity.

Mechanisms for the Specific Properties of γ-Hydroxybutyrate in Brain

γ-Hydroxybutyrate (GHB) is both a natural brain compound with neuromodulatory properties at central GABAergic synapses (micromolar concentration range) and also a drug (Xyrem(R) ) clinically used for the treatment of various neurological symptoms (millimolar dose range). However, this drug has abuse potential and can be addictive for some patients. Here, we review the basic mechanistic role of endogenous GHB in brain as well as the properties and mechanisms of action for therapeutic clinical doses of exogenous GHB. Several hypotheses are discussed with a preference for a molecular mechanism that conciliates most of the findings available. This conciliatory model may help for the design of GHB-like drugs active at lower doses and devoid of major side effects.