Abstract
Binding of [3 H] ()-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine (MK-801) was significantly inhibited by the addition of sodium nitroprusside (SNP), a nitric oxide (NO) donor, at a concentration range of 0.1 μM to 0.1μ M in rat brain synaptic membranes. On the contrary, two other NO donors, S-nitroso-N-acetylpenicillamine and S-nitroso-L-glutathione, did not inhibit binding even at 0.1 mM. Similarly potent inhibition of [3 H]MK-801 binding was caused by the addition of potassium ferrocyanide, while potassium ferricyanide induced slight inhibition of binding at 0.1 mM. Both SNP and potassium ferrocyanide markedly inhibited binding of [3 H] glutamic (Glu) and [3 H] D,L-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acids, without significantly affecting that of [3H] glycine and [3H] 5,7-dichlorokynurenic acid. Further addition of Glu significantly exacerbated the inhibition by both SNP and potassium ferrocyanide at concentrations of 1—10 μM. Potent inhibition was also induced for [3H] MK- 801 binding by the treatment of synaptic membranes with either SNP or potassium ferrocyanide, followed by efficient washing which also inhibited [3H] MK-801 binding due to removal of endogenous agonists. By contrast, dithiothreitol clearly differentiated between inhibitory properties of SNP and potassium ferrocyanide on [3H] MK-801 binding in terms of reversibility of the inhibition following pretreatment and subsequent washing. These results suggest that SNP may interfere with opening processes of the native NMDA channel through molecular mechanisms different from those underlying the inhibition by potassium ferrocyanide at the NMDA recognition domain in a manner independent of the generation of NO radicals.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.