Premium
BAY K 8644, a 1,4‐Dihydropyridine Ca 2+ Channel Activator: Dissociation of Binding and Functional Effects in Brain Synaptosomes
Author(s) -
Rampe D.,
Janis R. A.,
Triggle D. J.
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb06096.x
Subject(s) - nitrendipine , synaptosome , dihydropyridine , dissociation constant , chemistry , activator (genetics) , biophysics , guinea pig , depolarization , binding site , antagonist , calcium , endocrinology , medicine , biochemistry , biology , receptor , membrane , organic chemistry
K + ‐stimulated 45 Ca 2+ uptake into rat brain and guinea pig cerebral cortex synaptosomes was measured at 10 s and 90 s at K + concentrations of 5–75 m M . Net increases in 45 Ca 2+ uptake were observed in rat and guinea pig brain synaptosomes. 45 Ca 2+ uptake under resting or depolarizing conditions was not increased by the 1,4‐dihydropyridine BAY K 8644, which has been shown to activate Ca 2+ channels in smooth and cardiac muscle. High‐affinity [ 3 H]nitrendipine binding in guinea pig synaptosomes ( K D = 1.2 × 10 ‐10 M , B max = 0.56 pmol mg ‐1 protein) was competitively displaced with high affinity (IC 50 , 2.3 × 10 ‐9 M ) by BAY K 8644. Thus high‐affinity Ca 2+ channel antagonist and activator binding sites exist in synaptosome preparations, but their relationship to functional Ca 2+ channels is not clear.