Nedvetsky P I, Konev S V, Rakovich A A, Petrenko S V, Mongin A A
Institute of Photobiology, National Academy of Sciences of Belarus, Minsk, 220072, Belarus.
Biochemistry (Mosc). 2000 Sep;65(9):1027-35.
Nitric oxide (NO) modulates processes of synaptic transmission at pre- and postsynaptic levels. In the present work we studied the mechanisms of action of NO on [gamma-14C]amino-n-butyric acid ([14C]GABA) release in rat cortical synaptosomes. NO donors--S-nitroso-L-cysteine and hydroxylamine (but not sodium nitroprusside)--inhibited the neurotransmitter efflux in a concentration range from 10 microM to 1 mM. Nitrosocysteine completely and selectively suppressed the Ca2+-dependent (vesicular) [14C]GABA release, while not affecting the Ca2+-independent component of the [14C]GABA transport. The influence of NO donors was not related to activation of guanylyl cyclase, since the membrane-permeable cGMP analog dibutyryl-cGMP did not mimic and the guanylyl cyclase inhibitor methylene blue did not change the NO effects. In contrast, the membrane-permeable SH-reagent N-ethylmaleimide (NEM) resembled the effects of NO donors on the Ca2+-dependent [14C]GABA release. The degree of inhibition of the release by nitrosocysteine, hydroxylamine, and NEM correlated with their ability to oxidize intra-synaptosomal SH-groups. These data suggest that synaptosomal sulfhydryl groups are the target for NO action at the presynaptic level. The NO-induced oxidation of thiols may be involved in physiological and, especially, pathological effects of nitric oxide in the central nervous system.
一氧化氮（NO）在突触前和突触后水平调节突触传递过程。在本研究中，我们研究了NO对大鼠皮质突触体中[γ-14C]氨基丁酸（[14C]GABA）释放的作用机制。NO供体——S-亚硝基-L-半胱氨酸和羟胺（但不包括硝普钠）——在10 microM至1 mM的浓度范围内抑制神经递质外流。亚硝基半胱氨酸完全且选择性地抑制了Ca2+依赖性（囊泡性）[14C]GABA释放，同时不影响[14C]GABA转运的Ca2+非依赖性成分。NO供体的影响与鸟苷酸环化酶的激活无关，因为膜通透性cGMP类似物二丁酰-cGMP不能模拟其作用，鸟苷酸环化酶抑制剂亚甲蓝也不会改变NO的作用。相反，膜通透性SH试剂N-乙基马来酰亚胺（NEM）的作用类似于NO供体对Ca2+依赖性[14C]GABA释放的影响。亚硝基半胱氨酸、羟胺和NEM对释放的抑制程度与其氧化突触体内SH基团的能力相关。这些数据表明，突触体巯基是NO在突触前水平作用的靶点。NO诱导的硫醇氧化可能参与一氧化氮在中枢神经系统中的生理作用，尤其是病理作用。
