Clearer demonstration of calcium/calmodulin-dependent events in synaptosomes by use of the differential effects of two calmodulin antagonists, N-(aminohexyl)-5-chloro-1-naphthalenesulfonamide and N-(6-aminohexyl)-1-naphthalenesulfonamide.
1. In order to demonstrate more clearly calcium/calmodulin-dependent events, the differential effects of two calmodulin antagonists, W-7 and W-5, on synapsin I phosphorylation and norepinephrine release associated with calcium influx, were investigated using 32Pi in synaptosomes derived from rat cerebral cortex. 2. The calcium ionophore (A23187)-stimulatory effect on synapsin I phosphorylation and norepinephrine release was markedly reduced by W-7 and slightly reduced by W-5; whereas neither the strong nor the weak calmodulin antagonist had an effect on A23187-stimulated synaptosomal uptake of calcium. 3. Preincubation with H-8 reduced both W-5- and W-7-inhibited A23187-stimulated synapsin I phosphorylation by the same amount but did not affect their inhibitory effect nor the ionophore-stimulated norepinephrine release, thereby suggesting that W-5 may serve as an appropriate control for non-calmodulin-mediated effect of both calmodulin antagonists.
Imai
S
S
Department of Anatomy, Gifu University School of Medicine, Japan.
Onozuka
M
M
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002147:Calmodulin / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains; D013449:Sulfonamides / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects / Q000502:physiology*
D002147:Calmodulin; D013449:Sulfonamides; D000001:Calcimycin; C017967:W 7; C034700:N-(6-aminohexyl)-1-naphthalenesulfonamide; D002118:Calcium; D009638:Norepinephrine