The effects of metabotropic glutamate receptor 7 allosteric agonist N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride on developmental sevoflurane neurotoxicity: role of extracellular signal-regulated kinase 1 and 2 mitogen-activated protein kinase signaling pathway.

The present study was designed to evaluate the possible neuroprotective effects of metabotropic glutamate receptor (mGluR7) allosteric agonist N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082) on developmental sevoflurane neurotoxicity. To achieve the objective, hippocampal cultures (7 DIV, 7 day in vitro) were treated with different doses of L-(+)-2-amino-4-phosphonobutyric acid (L-AP4, an agonist of group III mGluRs), (RS)-α-Methylserine-O-phosphate (MSOP, an antagonist of group III mGluRs), AMN082 or cis-2-[[(3,5-dichlorophenyl)amino]carbonyl]cyclohexanecarboxylic acid (VU0155041, an agonist of mGluR4) before exposed to sevoflurane. Cell apoptosis were determined by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL)-staining. For in vivo study, rat pups (7 PND, 7 postnatal day) were injected with AMN082, L-AP4 or saline before sevoflurane exposure. Extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38, caspase-3, Bcl-2, and Bax were detected by Western blot. The locomotor activity and cognitive functions were evaluated by open-field test and Morris water maze (MWM), respectively. We found that L-AP4 prevented sevoflurane-induced cell apoptosis, but MSOP promoted. Specially, application of AMN082 contributed to the relief of sevoflurane-induced apoptosis in vitro, whereas VU0155041 did not. In addition, sevoflurane treatment led to a decrease of Bcl-2 and an increase of caspase-3 and Bax, which were mitigated by AMNO82 in vivo. Moreover, we showed that sevoflurane treatment resulted in a remarkable suppression of phospho-ERK1/2, which was restored by AMN082. Application of U0126 (an inhibitor of MEK) abolished the neuroprotective effects of AMN082 on sevoflurane neurotoxicity both in vitro and in vivo. In addition, sevoflurane exposure also led to an increase of phospho-JNK, but SP600125 (an inhibitor of JNK) did not attenuate sevoflurane-induced apoptosis. The total and phosphorylated p38 remained unchanged in sevoflurane-treated rat pups. Finally, AMN082 improved the learning and memory defects caused by postnatal sevoflurane exposure without alternations in emotion or locomotor activity. These preliminary data indicate that AMN082 may protect immature brain against sevoflurane neurotoxicity, and the ERK1/2 MAP kinase signaling is likely to be involved. Further studies are needed to fully assess the neuroprotective role of mGluR7 agonist AMN082 in developmental anesthetic neurotoxicity.

The effect of timing of application of positive end-expiratory pressure on oxygenation during one-lung ventilation.

Many studies have confirmed that applying positive end-expiratory pressure (PEEP) to the dependent lung during one-lung ventilation (OLV) improves oxygenation. Our purpose was to investigate the best time and level of PEEP application. Thirty patients undergoing thoracic surgery were randomised into three groups. After 20 minutes of two-lung ventilation (TLV) in the lateral position, all patients received OLV for one hour During OLV, 0, 5, 10 cmH2O PEEP were applied in order in group A, with each level sustained for 20 minutes. Group B had 5 cmH2O PEEP applied and maintained for one hour Patients in group C received PEEP with levels set in the opposite order to that of group A. The ventilation model was then converted to TLV. PaO2, PaCO2 and respiratory mechanical variables were compared at five different time points among groups, 20 minutes after TLV (T1), 20 (T2), 40 (T3) and 60 minutes (T4) after OLV and 20 minutes after conversion to TLV (T5). We found that PaO2 was lower in group A than the other two groups at T2 (P <0.05). PaO2 decreased significantly at T5 compared with T1 (P <0.05) in group A only. When PEEP was set to 10 cmH2O, the airway pressure increased significantly (P <0.05). These findings indicate that PEEP applied at the initial time of OLV improves oxygenation most beneficially. Five cmH2O PEEP may produce this beneficial effect without the increase in airway pressure associated with 10 cmH2O PEEP.

[Preliminary separation and identification of the neurotrophic substances from dorsal spinal cord of chicken embryos].

Extracts of spinal dorsal horn and ventral horn of chicken embryos hatched for 9 days were separated by Sephadex G-75 gel filtration, and different chromatographic fractions of DI and DII, VI and VII were obtained. The neurite-outgrowth promoting effects of the various fractions were assayed by the dorsal root ganglion (DRG) culture in vitro. It was shown that DII, but not DI, fraction of the dorsal horn extract exhibited a significant neurite-outgrowth promoting effect on DRG. By means of SDS-PAGE, the molecular weight of DII fraction ranged from 61 to 15 kD. VI and VII fraction of ventral horn showed no obvious effect on neurit-outgrowth of DRG in vitro.

[The neurite-outgrowth promoting effect from Clarke's nucleus of cat spinal cord with spared dorsal root preparation under electro-acupuncture stimulation on dorsal root ganglion of chicken embryo].

A modification of the double-coverslip hanging-drop culture technique originated from Maximow was introduced in the present report. The neurite - outgrowth promoting effect from Clarke's nucleus of cat spinal cord with partially lumbosacral dorsal rhizotomy as well as acupuncture stimulation of the points located within the peripheral innervating field of the spared dorsal root was examined with the modified culture technique. Findings demonstrated that an increased neurite-outgrowth promoting effect appeared in Clarke's nucleus of cat spinal cord with partial deafferentation, and that electro-acupuncture stimulation could enhance the neurite-outgrowth promoting effect further. It suggested that the increment of the neurite-outgrowth promoting effect might be related to the collateral sprouting of spared dorsal root and to the sprouting-promotion effect of acupuncture stimulation.