Differential effects of short- and long-term zolpidem treatment on recombinant α1β2γ2s subtype of GABA(A) receptors in vitro

Diazepam-Induced Down-Regulation of The Gabaa Receptor α1 Subunit, as Mediated by the Activation of L-Type Voltage-Gated Calcium Channel/Ca2+/Protein Kinase A Signaling Cascade

Benzodiazepines are among the most prescribed drug class worldwide to treat disorders such as anxiety, insomnia, muscle spasticity, and convulsive disorders, and to induce presurgical sedation. Although benzodiazepines exhibit a high therapeutic index and low toxicity in short-term treatments, prolonged administration induces tolerance to most of their therapeutic actions. The mechanism of this tolerance remains unclear. The central actions of benzodiazepines are mediated by binding to GABA_A receptors, which mediate most fast inhibitory transmission in the brain. The majority of GABA_A receptors are composed of two α-(1-6), two β-(1-3) and one γ-subunits (1-3). In a previous report, we demonstrated that the prolonged exposure of cerebrocortical neurons to diazepam produces a transcriptional repression of the GABA_A receptor α1 subunit gene via a mechanism dependent on the activation of L-type voltage-gated calcium channels (L-VGCCs). The results reported here confirm that the diazepam-induced downregulation of the α1 subunit is contingent upon calcium influx from extracellular space. In addition, this regulatory mechanism involves the activation of protein kinase A (PKA) and is accompanied by the activation of two transcription factors, the cAMP-response element-binding protein (CREB) and the inducible cAMP early repressor (ICER). Together, our results suggest that diazepam's activation of an L-VGCC/Ca²⁺/PKA/CREB-ICER signaling pathway is responsible for the regulation of GABA_A receptors. This elucidation of the intracellular signaling cascade activated by a prolonged benzodiazepine exposure, itself potentially involved in the development of tolerance, may contribute to locating molecular targets for future therapeutic interventions.

Neuroprotective effect of zolpidem against glutamate-induced toxicity is mediated via the PI3K/Akt pathway and inhibited by PK11195

Excitotoxicity is a pathological process in which neuronal dysfunction and death are induced by excessive glutamate stimulation, the major fast excitatory neurotransmitter in the mammalian brain. Excitotoxicity-induced neurodegeneration is a contributing factor in ischemia-induced brain damage, traumatic brain injury, and various neurodegenerative diseases. It is triggered by calcium overload due to prolonged over-activation of ionotropic N-methyl-d-aspartate (NMDA) receptors. Enhanced Ca²⁺ release results in neuronal vulnerability through several intertwined mechanisms, including activation of proteolytic enzymes, increased production of reactive oxygen species (ROS), mitochondrial dysfunction and modulation of intracellular signalling pathways. We investigated the neuroprotective effect of hypnotic zolpidem, a drug that exerts its central effects at the GABA_A receptor complex, against glutamate-induced toxicity in P19 neurons. Zolpidem prevented death of P19 neurons exposed to glutamate, and abolished the glutamate-induced increase in ROS production, p53 and Bax expression, and caspase-3/7 activity. Zolpidem effects were mediated by marked over-activation of Akt kinase. The pro-survival effect, as well as the pAkt induction, were prevented in the presence of wortmannin, an inhibitor of phosphatidylinositol-3-kinase (PI3K) that functions upstream of Akt. The beneficial effect of zolpidem on neuronal survival was not prevented by flumazenil, a GABA_A receptor antagonist. PK11195, a drug that modulates the mitochondrial translocator protein 18 kDa (TSPO) and F₀F₁-ATPase, prevented the beneficial effect of zolpidem, indicating that the mechanism of zolpidem action involves preservation of mitochondrial function and integrity. Zolpidem effects were further mediated by prevention of glutamate-induced increase in the expression of the NR2B subunit of NMDA receptor. The obtained results suggest the promising therapeutic potential of zolpidem against excitotoxic insults and highlight the importance of mitochondria and the Akt pathway as valuable targets for therapeutic interventions in glutamate-mediated neuropathological conditions.

Dependence, misuse, and beliefs regarding use of hypnotics by elderly psychiatric patients taking zolpidem, estazolam, or flunitrazepam

INTRODUCTION

To examine the prevalence rates and correlates of dependence on, misuse of, and beliefs regarding use of hypnotics in elderly psychiatric patients with long-term use of zolpidem, estazolam, or flunitrazepam.

METHODS

A total of 139 psychiatric outpatients 65 or more years of age who used zolpidem, estazolam, or flunitrazepam for at least 3 months were studied. The levels of hypnotic dependence and beliefs regarding hypnotic use (necessity and concern) were assessed. Three patterns of hypnotic misuse in the past 1 month were also explored. The correlates of high dependence, misuse, and unfavorable attitude and high concern toward hypnotic use were examined using logistic regression analyses.

RESULTS

A total of 28.8%, 7.9%, 12.2%, and 22.3% of participants reported high dependence on, misuse of, unfavorable attitude toward, and high concern toward hypnotic use, respectively. Males were more likely to report unfavorable attitude toward hypnotic use than females. Elders with significant depression were more likely to report high concern toward hypnotic use than those without significant depression. Elders with high concern toward hypnotic use were more likely to report high dependence on hypnotics than those with low concern. Elders with significant depression and taking zolpidem were more likely to misuse hypnotics than those without significant depression and taking estazolam or flunitrazepam, respectively.

DISCUSSION

Clinicians should monitor the possibility of dependence on and misuse of hypnotics among elderly psychiatric patients who had the correlates identified in this study.

Risk of Type 2 Diabetes in Patients With Nonapnea Sleep Disorders in Using Different Types of Hypnotics: A Population-Based Retrospective Cohort Study

There has been insufficient evidence on whether exposure to hypnotics affects the risk of type 2 diabetes (T2DM). The aim of this study was to examine patients with nonapnea sleep disorders using zolpidem, benzodiazepines (BZDs), or a combination of both, and their risk of T2DM. This was a population-based retrospective cohort study using data from 1997 to 2011. Data from the Taiwan National Health Insurance Research Database were employed for this study. A total of 45,602 patients with nonapnea sleep disorders and use of hypnotics were identified as the study cohort. The control cohort comprised 40,799 age- and sex-matched patients. We conducted a Cox proportional hazard regression analysis to estimate the effects of hypnotics on risk of T2DM. The overall incidence of T2DM was 20.1 per 1000 person-years for patients using zolpidem, which was significantly higher than that of the control group (11.9 per 1000 person-years). Overall, patients with nonapnea sleep disorders using zolpidem had a higher risk of T2DM compared with patients not using zolpidem and the control cohort (adjusted hazard ratio [HR] = 1.41, 95% confidence interval [CI] = 1.35-1.48). We also observed a significantly higher risk of T2DM in patients with both zolpidem and BZD use (adjusted HR = 1.77, 95% CI = 1.64-1.91) than that of those without zolpidem use and BZD use. Compared with patients not using hypnotics, patients using zolpidem had a higher risk of developing T2DM; the risk was particularly pronounced in those using both zolpidem and BZDs.

Correlates of dependence and beliefs about the use of hypnotics among zolpidem and zopiclone users

BACKGROUND

Zolpidem and zopiclone are the two most commonly prescribed Z-drugs approved to treat insomnia.

OBJECTIVES

To examine the demographic and clinical correlates of dependence and beliefs about hypnotic use among long-term zolpidem and zopiclone users in psychiatric treatment for insomnia.

METHODS

A total of 392 psychiatric outpatients who received zolpidem or zopiclone treatment for at least 3 months for insomnia were studied. Participants' severity of hypnotic dependence and beliefs about the use of hypnotics to treat sleep problems were assessed. The correlation of dependence and beliefs about zolpidem and zopiclone treatment with demographic characteristics, hypnotic-using behaviors, co-use of addictive substances, and depressive symptoms were analyzed using multiple regression analysis models.

RESULTS

Zolpidem users reported more severe dependence and a lower level of necessity regarding the use of hypnotics than zopiclone users did. High equivalent doses of hypnotics and long duration of use were significantly associated with severe dependence and a low level of necessity. Severe depressive symptoms were signiciantly associated with severe dependence, a low level of necessity, and a low level of concern. Educational level was also associated with the levels of concern and necessity. Conclusions/Importance: There were differences in the level of dependence and belief about hypnotic use between zolpidem and zopiclone users. The correlates of dependence and belief identified in this study can serve as the basis for prevention and intervention programs.