Effects of nitric oxide donors on Ca2+-dependent [14C]GABA release from brain synaptosomes: the role of SH-groups.
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.
Nedvetsky
P I
PI
Institute of Photobiology, National Academy of Sciences of Belarus, Minsk, 220072, Belarus.
Konev
S V
SV
Rakovich
A A
AA
Petrenko
S V
SV
Mongin
A A
AA
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003995:Dibutyryl Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000378:metabolism; D019811:Hydroxylamine / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008751:Methylene Blue / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D026403:S-Nitrosothiols; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013574:Synaptosomes / Q000378:metabolism*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology*
D002247:Carbon Isotopes; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D026403:S-Nitrosothiols; D013439:Sulfhydryl Reagents; D009599:Nitroprusside; D019811:Hydroxylamine; D003995:Dibutyryl Cyclic GMP; D005680:gamma-Aminobutyric Acid; C021315:S-nitrosocysteine; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D003545:Cysteine; D005033:Ethylmaleimide; D011188:Potassium; D002118:Calcium; D008751:Methylene Blue