ABSTRACT
The principal inhibitory transmitter, γ-aminobutyric acid (GABA), is critical for maintaining hypothalamic homeostasis and released from neurons phasically, as well as from astrocytes tonically. Although astrocytes in the arcuate nucleus (ARC) of the hypothalamus are shown to transform into reactive astrocytes, the tonic inhibition by astrocytic GABA has not been adequately investigated in diet-induced obesity (DIO). Here, we investigated the expression of monoamine oxidase- B (MAOB), a GABA-synthesizing enzyme, in reactive astrocytes in obese mice. We observed that a chronic high-fat diet (HFD) significantly increased astrocytic MAOB and cellular GABA content, along with enhanced hypertrophy of astrocytes in the ARC. Unexpectedly, we found that the level of tonic GABA was unaltered in chronic HFD mice using whole-cell patch-clamp recordings in the ARC. Furthermore, the GABA-induced current was increased with elevated GABA A receptor α5 (GABRA5) expression. Surprisingly, we found that a nonselective GABA transporter (GAT) inhibitor, nipecotic acid (NPA)-induced current was significantly increased in chronic HFD mice. We observed that GAT1 inhibitor, NO711-induced current was significantly increased, whereas GAT3 inhibitor, SNAP5114-induced current was not altered. The unexpected unaltered tonic inhibition was due to an increase of GABA clearance in the ARC by neuronal GAT1 rather than astrocytic GAT3. These results imply that increased astrocytic GABA synthesis and neuronal GABA A receptor were compensated by GABA clearance, resulting in unaltered tonic GABA inhibition in the ARC of the hypothalamus in obese mice. Taken together, GABA-related molecular pathways in the ARC dynamically regulate the tonic inhibition to maintain hypothalamic homeostasis against the HFD challenge.
ABSTRACT
Monoamine oxidase B (MAOB) is a key enzyme for GABA production in astrocytes in several brain regions. To date, the role of astrocytic MAOB has been studied in MAOB null knockout (KO) mice, although MAOB is expressed throughout the body. Therefore, there has been a need for genetically engineered mice in which only astrocytic MAOB is targeted. Here, we generated an astrocyte-specific MAOB conditional KO (cKO) mouse line and characterized it in the cerebellar and striatal regions of the brain. Using the CRISPR-Cas9 gene-editing technique, we generated Maob floxed mice (B6-Maob em1Cjl /Ibs) which have floxed exons 2 and 3 of Maob with two loxP sites. By crossing these mice with hGFAP-CreER T2 , we obtained Maob floxed::hGFAP-CreER T2 mice which have a property of tamoxifen-inducible ablation of Maob under the human GFAP (hGFAP) promoter. When we treated Maob floxed::hGFAP-CreER T2 mice with tamoxifen for 5 consecutive days, MAOB and GABA immunoreactivity were significantly reduced in striatal astrocytes as well as in Bergmann glia and lamellar astrocytes in the cerebellum, compared to sunflower oil-injected control mice. Moreover, astrocyte-specific MAOB cKO led to a 74.6% reduction in tonic GABA currents from granule cells and a 76.8% reduction from medium spiny neurons. Our results validate that astrocytic MAOB is a critical enzyme for the synthesis of GABA in astrocytes. We propose that this new mouse line could be widely used in studies of various brain diseases to elucidate the pathological role of astrocytic MAOB in the future.
ABSTRACT
BACKGROUND: There are few studies about the effective dose (ED) of propofol for anesthetic induction in Korean. The purpose of this study is to estimate the ED of propofol for anesthetic induction in Korean. METHODS: We studied 120 patients, who were class I or II of ASA physical status. All patients were allocated to six dose groups. Each dose group consisted of 10 men and 10 women. They were administered each 1.0 mg/kg, 1.4 mg/kg, 1.6 mg/kg, 1.8 mg/kg, 2.0 mg/kg and 2.2 mg/kg of propofol. Propofol was injected intravenously within 15 seconds. During 100% oxygen through mask ventilation, we evaluated response for verbal command and gentle shaking every 30 seconds. The end point was unconsciousness that patients fell the bar gripped with their hand. We recorded BIS value at end point. The ED estimates were calculated by logit model. Result were expressed as mean +/- SD or 95% confidence interval. RESULTS: The ED5, ED25, ED50, ED75, and ED95 of falling the bar were 1.05 mg/kg (95% CI:0.7-1.24), 1.41 mg/kg (95% CI:1.17-1.6), 1.67 mg/kg (95% CI:1.47-2.0), 1.99 mg/kg (95% CI:1.73-2.67), 2.66 mg/kg (95% CI:2.16-4.58). CONCLUSIONS: The ED50 and ED95 of falling object response were 1.67 mg/kg, 2.66 mg/kg. The appropriate induction dosage of propofol is 2.66 mg/kg without premedication.
Subject(s)
Female , Humans , Male , Hand , Hand Strength , Logistic Models , Masks , Oxygen , Premedication , Propofol , Unconsciousness , VentilationABSTRACT
BACKGROUND: This study compared the hemodynamic response and recovery profile of remifentanil-sevoflurane anesthesia for a pediatric tonsillectomy with that of remifentanil-propofol anesthesia. METHODS: Fifty healthy children (4-10 yr) undergoing a tonsillectomy were randomly assigned to one of two groups. Anesthesia was induced with remifentanil 1 mcg/kg over 1 min, propofol 2 mg/kg, and rocuronium 0.8 mg/kg. Anesthesia was maintained with remifentanil 0.25 mcg/kg/min and propofol 6 mg/kg/h, or remifentanil 0.25 mcg/kg/min and sevoflurane 1.0 vol%. The propofol and sevoflurane dose was kept unchanged, and remifentanil was titrated according to the hemodynamic response. The perioperative hemodynamics, recovery time, and side effects were assessed. RESULTS: Remifentanil-based anesthesia with propofol or sevoflurane resulted in stable hemodynamics, but sevoflurane was associated with a significantly lower systolic blood pressure. The recovery times were similar for spontaneous ventilation, extubation, eye opening, orientation, and full recovery in both groups. The incidence of side effects was similar in both groups. CONCLUSIONS: Remifentanil/sevoflurane is as equally effective as remifentanil/propofol in pediatric patients. The hemodynamic stability is appropriate and the recovery from anesthesia is rapid.
Subject(s)
Child , Humans , Anesthesia , Blood Pressure , Hemodynamics , Incidence , Propofol , Tonsillectomy , VentilationABSTRACT
BACKGROUND: Some investigators have shown that nicorandil, a K(ATP) channel opener, depresses the neuromuscular transmission contraction of the skeletal muscle. However, others have reported that it improves the recovery of vecuronium relaxation and the myotonic activity of muscle. This study investigated the effect of nicorandil on rocuronium relaxation. METHODS: Hemidiaphragm-phrenic nerve preparations were obtained from male Sprague-Dawley rats (150-250 g). The preparations were bathed in Krebs' solution containing in (mM): NaCl 118, KCl 5, CaCl2 2.5, NaHCO3 30, KH2PO4 1, MgCl2 1 and glucose 11. The preparations were, then maintained at 32 degrees C and aerated with a mixture of 95% O2 and 5% CO2. Isometric forces that were generated in response to 0.1 Hz, and, 50 Hz for 1.9 seconds with supramaximal electrical stimulation (0.2 msec, rectangular) to the phrenic nerve were measured using a force transducer. The single twitch tension (ST) and peak tetanic tension (PTT) were calculated as % inhibition of the control, and the tetanic fade (TF), as % increase in the PTT. Each preparation was exposed to one of the 6 nicorandil concentrations (0.0, 0.625, 1.25, 2.5, 5, 10 micrometer), and the adequate volume of the rocuronium solution was cumulatively added to the tissue bath for a desired rocuronium concentration until there was an 80-90% decrease in the ST. The effect of rocuronium at each concentration was allowed to reach a steady state before the tension parameters were measured. The EC5, EC25, EC50, EC75, and EC95 of rocuronium for the ST, PTT and TF were calculated using a probit model. The differences between the EC50 of rocuronium according to the nicorandil concentrations were tested using a t-test and a Bonferroni's correction. RESULTS: 1.25 and 2.5 micrometer nicorandil shifted the cumulative concentration-response curves for the TF of rocuronium to the right. 5 and 10 micrometer nicorandil shifted the cumulative concentration-response curves for the ST of rocuronium to the left. CONCLUSIONS: Lower concentration of nicorandil may help maintain the tetanic contraction during rocuronium relaxation.