Phospholipase A2 activation by melittin enhances spontaneous glutamatergic excitatory transmission in rat substantia gelatinosa neurons
Phospholipase A2 activation by melittin enhances spontaneous glutamatergic excitatory transmission in rat substantia gelatinosa neurons
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DOI：
10.1016/j.neuroscience.2005.05.040
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发表时间：
2005-12
期刊：
影响因子：
3.3
通讯作者：
Hai-yuan Yue;T. Fujita;E. Kumamoto
中科院分区：
文献类型：
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作者：
Hai-yuan Yue;T. Fujita;E. Kumamoto
为了解磷脂酶A_2在伤害性信息传递中的作用，采用全细胞膜片钳技术，观察了分泌型磷脂酶A_2激活剂蜂毒素对大鼠脊髓胶状质神经元自发性兴奋性信息传递的影响。在高于0.5μM的浓度下，蜂毒肽以独立于河豚毒素的方式增加自发兴奋性突触后电流的振幅和频率;详细检查了后者的作用。在80%的被检神经元中（n=64），蜂毒素灌流3 min逐渐增加自发兴奋性突触后电流频率（1μM时增加65±6%; n=51），并呈剂量依赖性（半数最大效应的有效浓度=1.1μM）。这种作用在洗脱后3分钟内消退。蜂毒肽引起的自发兴奋性突触后电流频率增加被磷脂酶A2抑制剂4-溴非那丙烯酰溴（10μM）抑制，而不受环氧合酶抑制剂吲哚美辛（100μM）和脂氧合酶抑制剂去甲二氢愈创木酸（100μM）的影响。外源性花生四烯酸（50μM）也可引起自发兴奋性突触后电流频率的类似增加;该效应也不受环氧合酶或脂氧合酶抑制剂的影响。蜂毒肽未能增加自发兴奋性突触后电流的频率在名义上的Ca ~（2+）-免费或La ~（3+）-含有Krebs解决方案。我们的结论是，蜂毒肽增加自发释放L-谷氨酸胶状质神经元激活分泌型磷脂酶A2和增加Ca 2+内流通过电压门控Ca 2+通道在神经末梢，可能与花生四烯酸的参与，但不是其代谢产物产生的环氧合酶和脂氧合酶。考虑到胶状质在调节伤害性信息传递中起着重要作用，我们认为胶状质中分泌的磷脂酶A2激活可能正调节伤害性信息传递。
In order to know a role of phospholipase A2in modulating nociceptive transmission, the effect of a secreted phospholipase A2activator melittin on spontaneous glutamatergic excitatory transmission was investigated in substantia gelatinosa neurons of an adult rat spinal cord slice by using the whole-cell patch-clamp technique. Bath-applied melittin at concentrations higher than 0.5μM increased both the amplitude and the frequency of spontaneous excitatory postsynaptic current in a manner independent of tetrodotoxin; the latter effect of which was examined in detail. In 80% of the neurons examined (n=64), melittin superfused for 3 min gradually increased spontaneous excitatory postsynaptic current frequency (by 65±6% at 1μM; n=51) in a dose-dependent manner (effective concentration for half-maximal effect=1.1μM). This effect subsided within 3 min after washout. The spontaneous excitatory postsynaptic current frequency increase produced by melittin was reduced by the phospholipase A2inhibitor 4-bromophenacryl bromide (10μM) while being unaffected by the cyclooxygenase inhibitor indomethacin (100μM) and the lipoxygenase inhibitor nordihydroguaiaretic acid (100μM). A similar increase in spontaneous excitatory postsynaptic current frequency was produced by exogenous arachidonic acid (50μM); this effect was also unaffected by the cyclooxygenase or lipoxygenase inhibitor. Melittin failed to increase spontaneous excitatory postsynaptic current frequency in a nominally Ca2+-free or La3+-containing Krebs solution. We conclude that melittin increases the spontaneous release of l-glutamate to substantia gelatinosa neurons by activating secreted phospholipase A2and increasing Ca2+influx through voltage-gated Ca2+channels in nerve terminals, probably with an involvement of arachidonic acid but not its metabolites produced by cyclooxygenase and lipoxygenase. Considering that the substantia gelatinosa plays an important role in regulating nociceptive transmission, it is suggested that this transmission may be positively modulated by secreted phospholipase A2activation in the substantia gelatinosa.