The mRNA expression levels of GABAA receptor α1 and α2 subunits in patients with major depressive disorder during onset and remission

OBJECTIVE

We aimed to investigate the expression levels of GABA and GABA_A receptor α1 and α2 subunits in patients with major depressive disorder (MDD) during onset and remission.

MATERIALS AND METHODS

48 patients with MDD during onset and 45 patients with MDD during remission who were treated in our university were selected. Moreover, the control group included 46 healthy volunteers recruited in the community. The depression and anxiety symptoms were assessed by Hamilton Depression (HAMD) Scale and Hamilton Anxiety (HAMA) Scale. ELISA was used to determine the serum GABA levels. The mRNA expression of GABA_A receptor α1 and α2 subunits in peripheral blood were detected by RT-PCR.

RESULTS

The expression levels of serum GABA and of GABA_A receptor α1 and α2 subunits in MDD depression attack group were notably decreased in comparison with those in MDD remission group and control group ((4.10 ± 0.73) v.s. (5.91 ± 1.25) and (5.83 ± 1.17) umol/L, F = 5.61, p < 0.001; (0.53 ± 0.32) v.s. (0.91 ± 0.18) and (0.93 ± 0.21), F = 8.37, p < 0.001; (1.45 ± 0.86) v.s. (2.33 ± 1.49) and (2.28 ± 1.50), F = 8.23, p < 0.001). However, there were no marked difference in the levels of these three indices between the MDD remission group and the control group (p > 0.05). Serum GABA levels were negatively correlated with HAMA total score (r = -0.34, p = 0.02), HAMD total score (r = -0.46, p = 0.01) and depression core symptom score (r = -0.32, p = 0.03).

CONCLUSIONS

During the onset of MDD, there may be GABA neuronal dysfunction and abnormal expression of GABA_A receptor subunits, and those changes showed a state change, which gradually returned to normal during remission.

Electro-Acupuncture Attenuates Chronic Stress Responses via Up-Regulated Central NPY and GABA A Receptors in Rats

Stress can increase the release of corticotropin-releasing factor (CRF) in the hypothalamus, resulting in attenuation of gastric motor functions. In contrast, central neuropeptide Y (NPY) can reduce the biological actions of CRF, and in turn weaken stress responses. Although electroacupuncture (EA) at stomach 36 (ST-36) has been shown to have anti-stress effects, its mechanism has not yet been investigated. The effect of EA at ST-36 on the hypothalamus-pituitary-adrenal (HPA) axis and gastrointestinal motility in chronic complicated stress (CCS) conditions have not been studied and the inhibitory mechanism of NPY on CRF through the gamma-aminobutyric acid (GABA)_A receptor need to be further investigated. A CCS rat model was set up, EA at ST-36 was applied to the bilateral hind limbs every day prior to the stress loading. Further, a GABA_A receptor antagonist was intracerebroventricularly (ICV) injected daily. Central CRF and NPY expression levels were studied, serum corticosterone and NPY concentrations were analyzed, and gastric motor functions were assessed. CCS rats showed significantly elevated CRF expression and corticosterone levels, which resulted in inhibited gastric motor functions. EA at ST-36 significantly increased central NPY mRNA expression and reduced central CRF mRNA expression as well as the plasma corticosterone level, helping to restore gastric motor function. However, ICV administration of the GABA_A receptor antagonist significantly abolished these effects. EA at ST-36 upregulates the hypothalamic NPY system. NPY may, through the GABA_A receptor, significantly antagonize the overexpressed central CRF and attenuate the HPA axis activities in CCS conditions, exerting influences and helping to restore gastric motor function.

Polymorphism rs4263535 in GABRA1 intron 4 was related to deeper sedation by intravenous midazolam

OBJECTIVE

To evaluate whether polymorphisms in the gamma-aminobutyric acid A receptor α1 subunit (GABRA1) gene influence sleep induction time, bispectral index score (BIS) during sleep induction and the total dose of midazolam required to reach a Ramsay Sedation Assessment Scale (RSAS) score of 4.

METHODS

Patients scheduled for elective orthopaedic surgery were enrolled. All patients received initial doses of 0.02 mg/kg intravenous midazolam. If the RSAS score did not reach 4, an additional 1-mg dose of midazolam was administered. Results were compared among groups of patients with five single-nucleotide polymorphisms (SNPs) in GABRA1: rs4263535, rs980791, rs6556562, rs998754 and rs2279020.

RESULTS

A total of 104 patients were evaluated. Polymorphism rs4263535 was associated with the lowest BIS during sedation induction. Multinomial logistic regression analysis demonstrated that polymorphism rs4263535 was significantly associated with the total dose of midazolam required for sedation induction.

CONCLUSIONS

Polymorphism rs4263535 in GABRA1 intron 4 was associated with deeper sedation by intravenous midazolam. Patients with the A/A rs4263535 genotype required a smaller dose of midazolam.

Effect of midazolam on the proliferation of neural stem cells isolated from rat hippocampus

In many recent studies, the inhibitory transmitter gamma-aminobutyric acid has been shown to modulate the proliferation, differentiation and survival of neural stem cells. Most general anesthetics are partial or allosteric gamma-aminobutyric acid A receptor agonists, suggesting that general anesthetics could alter the behavior of neural stem cells. The neuroprotective efficacy of general anesthetics has been recognized for decades, but their effects on the proliferation of neural stem cells have received little attention. This study investigated the potential effect of midazolam, an extensively used general anesthetic and allosteric gamma-aminobutyric acid A receptor agonist, on the proliferation of neural stem cells in vitro and preliminarily explored the underlying mechanism. The proliferation of neural stem cells was tested using both Cell Counting Kit 8 and bromodeoxyuridine incorporation experiments. Cell distribution analysis was performed to describe changes in the cell cycle distribution in response to midazolam. Calcium imaging was employed to explore the molecular signaling pathways activated by midazolam. Midazolam (30–90 μM) decreased the proliferation of neural stem cells in vitro. Pretreatment with the gamma-aminobutyric acid A receptor antagonist bicuculline or Na-K-2Cl cotransport inhibitor furosemide partially rescued this inhibition. In addition, midazolam triggered a calcium influx into neural stem cells. The suppressive effect of midazolam on the proliferation of neural stem cells can be partly attributed to the activation of gamma-aminobutyric acid A receptor. The calcium influx triggered by midazolam may be a trigger factor leading to further downstream events.