HIGH-AFFINITY BINDING OF H-3 VERAPAMIL TO RAT-BRAIN SYNAPTIC MEMBRANEIS ANTAGONIZED BY PYRETHROID INSECTICIDES

Deltamethrin is a powerful neuroactive agent causing increased neurotr ansmitter release at the synapse. To understand the cause for such an action of this pyrethroid insecticide, we have studied its binding cha racteristics to the calcium channel by utilizing H-3-verapamil as a sp ecific ligand. It was found that deltamethrin is capable of competing at the same binding site as 3(H)-verapamil. Also, it was found that no nlabeled verapamil could reduce the binding of H-3-deltamethrin (teste d at 1 nM) to its binding site. The EC(50) value of verapamil to displ ace 50% of H-3-deltamethrin was in the order of 0.3 mu M, which coinci des with the approximate K-D value for this ligand to bind with calciu m channels in the rat brain synaptosomal plasma membranes.