alpha-Bungarotoxin binding properties of a central nervous system nicotinic acetylcholine receptor

Abstract

High-affinity, specific binding of radiolabeled alpha-bungarotoxin to particulate fractions derived from rat brain shows saturability (Bmax approximately 37fmol/mg, KDapp = 1.7 nM) and insenstivity to ionic strength, and is essentially irreversibel (Kon = 5 . 10(6) min-1 . mol-1; Kdisplacement = 1.9 . 10(-4) min-1, tau1/2 = 62 h). Subcellular distribution of specific sites is consistent with their location on synaptic junctional complex and post-synaptic membranes. These membrane-bound binding sites exhibit unique sensitivity to cholinergic ligands; pretreatment of membranes with cholinerin binding sites to a high affinity form toward agonist. The effect is most marked for the natural agonist, acetylcholine. These results strongly support the notion that the entity under study is an authentic nicotinic acetylcholine receptor.