Characterization of phenylalkylamine binding sites in insect (Periplaneta americana) nervous system and skeletal muscle membranes

Abstract

AbstractThis study has identified specific, stereoselective phenylalkylamine (PAA, (±)‐ [3H]verapamil) binding sites of low‐affinity and high‐density in cockroach (Periplaneta americana) nervous system and skeletal muscle membranes. Scatchard transformation of equilibrium binding data revealed a single population of binding sites in both tissues with dissociation constants (Kd) of 273 nM and 377 nM and binding capacities (Bmax) of 23 pmol·mg protein−1 and 37pmol·mg protein−1 for cockroach nervous tissue and skeletal muscle membranes, respectively. The PAA binding site in cockroach nervous tissue membranes was found to be dihydropyridine (DHP)‐insensitive, whereas the corresponding site in cockroach skeletal muscle membranes was DHP‐sensitive. This property of a DHP‐sensitive PAA receptor distinguishes the binding sites identified in cockroach skeletal muscle from those in cockroach nervous tissue and indicates that pharmacologically distinct putative Ca2+ channel subtypes are present in insect nerve and muscle. © 1993 Wiley‐Liss, Inc.