title: Effects of calcium antagonists on the evoked release of dynorphin A(1-8) and availability of intraterminal calcium in rat hippocampal mossy fiber synaptosomes.
abstract: The pharmacological properties of presynaptic calcium (Ca) channels on rat hippocampal mossy fiber synaptosomes were characterized by determining the inhibitory potencies for various classes of Ca antagonists on depolarization-induced Ca mobilization and the release of dynorphin A(1-8)-like immunoreactivity (Dyn-LI). Flunarizine and cinnarizine were the most potent inhibitors of both parameters (IC50 values less than 10(-5) M). Gadolinium and omega-conotoxin (omega-CgTx) were also effective inhibitors of Dyn-LI release (IC50 values less than 3 x 10(-5) M), but omega-CgTx only partially reduced the level of cytosolic free Ca. The release of Dyn-LI was relatively insensitive to both the L-type (dihydropyridines, verapamil and diltiazem) and T-type (amiloride and phenytoin) channel blockers. It appears that presynaptic N-type Ca channels make the most substantial contribution to the Ca influx required for the exocytosis of Dyn-LI from hippocampal mossy fiber nerve endings.
authors.affiliation: Department of Anatomy and Cell Biology, School of Medicine, East Carolina University, Greenville, NC 27858-4354.
authors.forename: D M
authors.initials: DM
authors.lastname: Terrian
authors.forename: D S
authors.initials: DS
authors.lastname: Damron
authors.forename: R V
authors.initials: RV
authors.lastname: Dorman
authors.forename: R L
authors.initials: RL
authors.lastname: Gannon
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002936:Cinnarizine / Q000494:pharmacology*; D004399:Dynorphins / Q000378:metabolism*; D005444:Flunarizine / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D010446:Peptide Fragments / Q000378:metabolism*; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D010446:Peptide Fragments; D002936:Cinnarizine; D004399:Dynorphins; C026770:dynorphin (1-8); D005444:Flunarizine; D002118:Calcium