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 IJM） decreased the proliferation of neural stem cells in vitro. Pretreatment with the gamma-aminobutyric acid A receptor antagonist bicuculline or Na-K-2CI 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.

Efficacy and Safety of Dexmedetomidine during Anesthesia Induction of Patients with Intracranial Tumor: A Preliminary Observational Trial

Background: The efficacy and safety of dexmedetomidine during the anesthesia induction of intracranial tumor patients remain unknown. We wondered whether loading infusion of dexmedetomidine 1 μg/kg over 10 min to intracranial tumor patients was as efficient and safe as to those abdominal disease patients. Methods: Patients aged 18-60 years, male or female, ASA I or II, scheduled for intracranial tumor resection (Group N, n = 30) or abdominal operation (Group A, n = 30) were enrolled in this observational trial. Dexmedetomidine was administrated with a loading dosage of 1 μg/kg over 10 min following with continuous infusing of 0.5 μg/kg/h. Fentanyl, propofol and rocuronium were sequentially administered for anesthesia induction. Heart rate (HR), blood pressure (BP), pulse oxygen saturation (SpO2), bispectral index (BIS) and other adverse effects were recorded from the beginning of loading infusion of dexmedetomidine to the end of endotracheal intubation. Results: Among with loading infusion, HR and BIS value decreased and were significantly lower at the end of infusion than before infusion (P P > 0.05). One patient of Group N dropped out from this trial because of a serious headache. 14 of 29 patients during dexmedetomidine loading infusion suffered hypoxemia (SpO2 P Conclusion: A loading dosage of 1 μg/kg of dexmedetomidine was not suitable for the anesthesia induction of intracranial tumor patients as compared to patients undergoing abdominal operation.

Propofol effectively inhibits lithium-pilocarpine-induced status epilepticus in rats via downregulation of N-methyl-D-aspartate receptor 2B subunit expression

Status epilepticus was induced via intraperitoneal injection of lithium-pilocarpine.The inhibitory effects of propofol on status epilepticus in rats were judged based on observation of behavior,electroencephalography and 24-hour survival rate.Propofol（12.5-100 mg/kg） improved status epilepticus in a dose-dependent manner,and significantly reduced the number of deaths within 24 hours of lithium-pilocarpine injection.Western blot results showed that,24 hours after induction of status epilepticus,the levels of N-methyl-D-aspartate receptor 2A and 2B subunits were significantly increased in rat cerebral cortex and hippocampus.Propofol at 50 mg/kg significantly suppressed the increase in N-methyl-D-aspartate receptor 2B subunit levels,but not the increase in N-methyl-D-aspartate receptor 2A subunit levels.The results suggest that propofol can effectively inhibit status epilepticus induced by lithium-pilocarpine.This effect may be associated with downregulation of N-methyl-D-aspartate receptor 2B subunit expression after seizures.

Propofol increases in vitro proliferation of cultured rat hippocampal precursor cells inhibited by corticosterone

BACKGROUND： Previous studies have shown that propofol enhances proliferation of cultured hippocampal precursor cells in vitro and increases proliferation of cultured hippocampal precursor cells inhibited by corticosterone. Because gamma-aminobutyric acid A （GABA-A） receptor is the functional target for propofol, the proliferative effects of propofol are thought to take place through GABA-A receptor. OBJECTIVE： To determine whether propofol enhances proliferation of rat hippocampal precursor cells inhibited by corticosterone by upregulating expression of GABA-A receptor. DESIGN, TIME AND SETTING： A comparative, observational, in vitro experiment was performed at the Beijing Institute of Pharmacology and Toxicology from April 2005 to April 2006. MATERIALS： Propofol was purchased from AstraZeneca, italy; corticosterone was purchased from Sigma, USA; bicuculline was purchased from Alexis, Switzerland. METHODS： Hippocampal precursor cells were isolated from newborn Wistar rats and cultured in vitro. The second passage of precursor cells was grouped according to the various drugs added to the culture medium： 0.5 μmol/L propofol; 2.5 pmol/L propofol; 100 μmol/L corticosterone; 10 μmol/L bicuculline; 100 μmol/L corticosterone and 0.5 μmol/L propofol; 100 μmol/L corticosterone and 2.5 μmol/L propofol; 100 μmol/L corticosterone, 10 μmol/L bicuculline, and 0.5 μmol/L propofol; 100 μmol/L corticosterone, 10 μmol/L bicuculline, and 2.5 μmol/L propofol; 100 μmol/L corticosterone and 10 pmol/L bicuculline. The cells were cultured for 24 hours with medium containing the respective concentration of drug. The control group consisted of precursor cells absent of drug treatment. MAIN OUTCOME MEASURES： The MTT and ^3H-TdR incorporation assays were used to detect proliferative effects of propofol and bicuculline on cultured rat hippocampal precursor cells inhibited by corticosterone. Immunocytochemistry was used to detect GABA-A receptor expression. Enzyme-linked irnmunosorbent assay was used to quantify GABA-A receptor expression. RESULTS： Propofol, at a concentration of 0.5 and 2.5 μmol/L, increased proliferation of cultured rat hippocampal precursor cells inhibited by corticosterone, while bicuculline antagonized the effects of propofol （P 〈 0.05 or P 〈 0.01 ）. Corticosterone （100μmol/L） decreased expression of GABA-A receptor in the hippocampal precursor cells （P〈 0.05）, and GABA-A receptor expression was upregulated when propofol （2.5μmol/L） was added to the culture medium （P〈 0.05）. CONCLUSION： Low concentrations of propofol increased expression of GABA-A receptor. These results suggest that GABA-A receptor is involved in increased proliferation of cortisone-inhibited rat hippocampal precursor cells in vitro.

Dopaminergic Neurons in the Ventral Tegmental–Prelimbic Pathway Promote the Emergence of Rats from Sevoflurane Anesthesia

Dopaminergic neurons in the ventral tegmental area(VTA)play an important role in cognition,emergence from anesthesia,reward,and aversion,and their projection to the cortex is a crucial part of the"bottom-up"ascending activating system.The prelimbic cortex(PrL)is one of the important projection regions of the VTA.However,the roles of dopaminergic neurons in the VTA and the VTADA–PrL pathway under sevoflurane anesthesia in rats remain unclear.In this study,we found that intraperitoneal injection and local microinjection of a dopamine D1 receptor agonist(Chloro-APB)into the PrL had an emergence-promoting effect on sevoflurane anesthesia in rats,while injection of a dopamine D1 receptor antagonist(SCH23390)deepened anesthesia.The results of chemogenetics combined with microinjection and optogenetics showed that activating the VTADA–PrL pathway prolonged the induction time and shortened the emergence time of anesthesia.These results demonstrate that the dopaminergic system in the VTA has an emergence-promoting effect and that the bottom-up VTADA–PrL pathway facilitates emergence from sevoflurane anesthesia.