GABA withdrawal syndrome: GABAA receptor, synapse, neurobiological implications and analogies with other abstinences

Developmental Toxicity Study of DL-4-Hydroxy-4-Phenylhexanamide (DL-HEPB) in Rats

Antiepileptic drugs affect embryonic development when administered during pregnancy, generating severe alterations, such as as cleft lip, spina bifida, heart abnormalities, or neuronal alterations. The compound DL-4-hydroxy-4-phenylhexanamide (DL-HEPB), a phenyl alcohol amide structurally different from known anticonvulsants, has shown good anticonvulsant effects in previous studies. However, its effects on intrauterine development are unknown. So, the purpose of this study was to determine the potential of DL-HEPB to produce alterations in conceptus. Pregnant Wistar rats were orally exposed to 0, 50, 100, and 200 mg/kg of DL-HEPB during organogenesis, and their food consumption and weight gain were measured. On gestation day 21, pregnant females were euthanized to analyze the fetuses for external, visceral, and skeletal malformations. A significant decrease in food consumption and body weight was observed in mothers, without any other manifestation of toxicity. In fetuses, no external malformations, visceral, or skeletal abnormalities, were observed under the dose of 100 mg/kg, while the dose of 200 mg/kg caused malformations in low frequency in brain and kidneys. In view of the results obtained, DL-HEPB could be a good starting point for the design of new highly effective anticonvulsant agents, with much lower developmental toxicity than that shown by commercial anticonvulsants.

High-dose lormetazepam dependence: strange case of Dr. Jekyll and Mr. Hyde

High-dose benzodiazepine (BZD) abuse is emerging as a substance use disorder (SUD). The aim of the study is to explore the impact of high-dose lormetazepam (LMZ) abuse and the characteristics of patients affected by this SUD in a tertiary referral addiction unit. We have retrospectively evaluated 1112 patients admitted to the Addiction Medicine Unit, Verona University Hospital, Italy for detoxification from high-dose BZD dependence. LMZ was the most common BZD, with an increasing prevalence from January 2003 to June 2018. Socio-demographic (more women; higher age and education) and clinical features (higher daily diazepam dosage equivalent, BZD abuse duration, age of first BZD intake; BZD prescribed more frequently for sleep disorders; less frequent history of other SUDs, previous/active alcohol, previous opioids abuse; more frequent overall major psychiatric diseases and major depression; less-frequent bipolar disorders and other psychoses, personality disorders, and more than one psychiatric disease) of LMZ vs. other BZD abusers significantly differed. 96.7% LMZ abusers took oral solution, while two-thirds of other BZD abusers took tablets. Oral solution, BZD abuse duration and prescription of BZD for sleep disorders increased, while history of other SUDs, previous/active alcohol and active cannabinoids SUD reduced the risk of high-dose LMZ vs. other BZDs abuse. The large prevalence of high-dose LMZ abusers in Italy may be strongly related to the availability and characteristics of oral formulation that may transform the innocuous Dr. Jekyll tablets into an evil Mr. Hyde. Restriction to the market of LMZ oral formulation might reduce the risk of high-dose abuse.

De Novo Myoclonic Status Epilepticus After Benzodiazepine Withdrawal

Myoclonic status epilepticus (MSE) in patients without epilepsy, or de novo MSE, is a rare condition associated with several acute symptomatic etiologies, including drugs and toxins. We describe a 94-year-old woman with Alzheimer dementia and long use of mirtazapine 30 mg/d and alprazolam 1 mg/d who developed MSE approximately 24 hours after abrupt discontinuation of alprazolam. The patient was taking sulfamethoxazole/trimethoprim for urinary tract infection, diagnosed 2 weeks before admission. She had no history of seizures. Routine laboratory examinations were normal and head computed tomography showed no acute injuries. She received a loading dose of 1000 mg of intravenous valproate (VPA). Continuous electroencephalogram monitoring revealed very frequent generalized spikes and polyspikes in a markedly slowed background activity. Intravenous VPA 500 mg thrice a day and alprazolam 0.5 mg twice a day were prescribed, and antibiotic was switched to piperacillin/tazobactam. Myoclonic jerks ceased completely and electroencephalogram showed no epileptiform discharges 2 days after VPA treatment onset, with recovery of baseline neurological status. This is, to the best of our knowledge, the first report of de novo MSE related to abrupt discontinuation of benzodiazepines. Seizures and status epilepticus are potential adverse events after abrupt withdrawal of chronically used benzodiazepines, especially in conditions with intrinsic epileptogenic susceptibility, such as Alzheimer disease.

Low risk of seizures with slow flumazenil infusion and routine anticonvulsant prophylaxis for high-dose benzodiazepine dependence

High-dose benzodiazepine (BZD) dependence represents an emerging and under-reported addiction phenomenon and is associated with reduced quality of life. To date there are no guidelines for the treatment of high-dose BZD withdrawal. Low-dose slow flumazenil infusion was reported to be effective for high-dose BZD detoxification, but there is concern about the risk of convulsions during this treatment. We evaluated the occurrence of seizures in 450 consecutive high-dose BZD dependence patients admitted to our unit from April 2012 to April 2016 for detoxification with low-dose slow subcutaneous infusion of flumazenil associated with routine anticonvulsant prophylaxis. In our sample, 22 patients (4.9%) reported history of convulsions when previously attempting BZD withdrawal. Only four patients (0.9%) had seizures during ( n = 2) or immediately after ( n = 2) flumazenil infusion. The two patients with seizures during flumazenil infusion were poly-drug misusers. The most common antiepileptic drugs (AEDs) used for anticonvulsant prophylaxis were either valproate 1000 mg or levetiracetam 1000 mg. Our data indicate that, when routinely associated with AEDs prophylaxis, low-dose slow subcutaneous flumazenil infusion represents a safe procedure, with low risk of seizure occurrence.

Short-term and long-term effects of diazepam on the memory for discrimination and generalization of scopolamine

Benzodiazepines are among the most widely prescribed and misused psychopharmaceutical drugs. Although they are well-tolerated, they are also capable of producing amnestic effects similar to those observed after pharmacological or organic cholinergic dysfunction. To date, the effect of benzodiazepine diazepam on the memory for discrimination of anticholinergic drugs has not been reported. The aim of the present study was to analyze the immediate and long-term effects of diazepam on a drug discrimination task with scopolamine. Male Wistar rats were trained to discriminate between scopolamine and saline administration using a two-lever discrimination task. Once discrimination was acquired, the subjects were divided into three independent groups, (1) control, (2) diazepam, and (3) diazepam chronic administration (10 days). Subsequently, generalization curves for scopolamine were obtained. Additionally, the diazepam and control groups were revaluated after 90 days without having been given any other treatment. The results showed that diazepam produced a significant reduction in the generalization gradient for scopolamine, indicating an impairment of discrimination. The negative effect of diazepam persisted even 90 days after drug had been administered. Meanwhile, the previous administration of diazepam for 10 days totally abated the generalization curve and the general performance of the subjects. The results suggest that diazepam affects memory for the stimulus discrimination of anticholinergic drugs and does so persistently, which could be an important consideration during the treatment of amnesic patients with benzodiazepines.

NMDA Receptors and NO:cGMP Signaling Pathway Mediate the Diazepam-Induced Sensitization to Withdrawal Signs in Mice

The goal of the present study was to examine the effects of N-methyl-aspartate (NMDA) receptor antagonists-memantine and ketamine and the drugs modifying the NO:cGMP pathway-NG-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI), the endogenous precursor of NO-L-arginine, and the guanylyl cyclase inhibitor-methylene blue (MB) on the development of sensitization to withdrawal signs precipitated after chronic, interrupted treatment with diazepam, a benzodiazepine receptor agonist, in mice. To develop the sensitization, the mice were divided into groups: continuously and sporadically (with two diazepam-free periods) treated with diazepam (15 mg/kg, sc). To precipitate the withdrawal syndrome (clonic and tonic seizures, and death), pentylenetetrazole (55 mg/kg, sc) with the benzodiazepine receptor antagonist, flumazenil (5.0 mg/kg, ip), were administered after the last injection of diazepam or saline. Memantine (2.5, 5.0 mg/kg), and ketamine (2.5, 5.0 mg/kg), L-NAME (100, 200 mg/kg) and 7-NI (20 and 40 mg/kg), L-arginine (250, 500 mg/kg) and MB (5 and 10 mg/kg) were administered ip in sporadically diazepam-treated mice during the diazepam-free periods. Our results indicated that both NMDA receptor antagonists and drugs that inhibit the NO:cGMP pathway, except L-arginine (the endogenous donor of NO), attenuated the diazepam-induced sensitization to withdrawal signs in mice. Thus, NMDA receptors and the NO:cGMP pathway are involved in the mechanisms of sensitization to benzodiazepine withdrawal.

Curcumol allosterically modulates GABA(A) receptors in a manner distinct from benzodiazepines

Inhibitory A type γ-aminobutyric acid receptors (GABA_ARs) play a pivotal role in orchestrating various brain functions and represent an important molecular target in neurological and psychiatric diseases, necessitating the need for the discovery and development of novel modulators. Here, we show that a natural compound curcumol, acts as an allosteric enhancer of GABA_ARs in a manner distinct from benzodiazepines. Curcumol markedly facilitated GABA-activated currents and shifted the GABA concentration-response curve to the left in cultured hippocampal neurons. When co-applied with the classical benzodiazepine diazepam, curcumol further potentiated GABA-induced currents. In contrast, in the presence of a saturating concentration of menthol, a positive modulator for GABA_AR, curcumol failed to further enhance GABA-induced currents, suggesting shared mechanisms underlying these two agents on GABA_ARs. Moreover, the benzodiazepine antagonist flumazenil did not alter the enhancement of GABA response by curcumol and menthol, but abolished that by DZP. Finally, mutations at the β2 or γ2 subunit predominantly eliminated modulation of recombinant GABA_ARs by curcumol and menthol, or diazepam, respectively. Curcumol may therefore exert its actions on GABA_ARs at sites distinct from benzodiazepine sites. These findings shed light on the future development of new therapeutics drugs targeting GABA_ARs.

Transcriptomic immaturity of the hippocampus and prefrontal cortex in patients with alcoholism

Alcoholism, which is defined as the recurring harmful use of alcohol despite its negative consequences, has a lifetime prevalence of 17.8%. Previous studies have shown that chronic alcohol consumption disrupts various brain functions and behaviours. However, the precise mechanisms that underlie alcoholism are currently unclear. Recently, we discovered “pseudo-immature” brain cell states of the dentate gyrus and prefrontal cortex (PFC) in mouse models of psychotic disorders and epileptic seizure. Similar pseudo-immaturity has been observed in patients with psychotic disorders, such as schizophrenia and bipolar disorder. Patients with alcoholism occasionally exhibit similar psychological symptoms, implying shared molecular and cellular mechanisms between these diseases. Here, we performed a meta-analysis to compare microarray data from the hippocampi/PFCs of the patients with alcoholism to data from these regions in developing human brains and mouse developmental data for specific cell types. We identified immature-like gene expression patterns in post-mortem hippocampi/PFCs of alcoholic patients and the dominant contributions of fast-spiking (FS) neurons to their pseudo-immaturity. These results suggested that FS neuron dysfunction and the subsequent imbalance between excitation and inhibition can be associated with pseudo-immaturity in alcoholism. These immaturities in the hippocampi/PFCs and the underlying mechanisms may explain the psychotic symptom generation and pathophysiology of alcoholism.