CHARACTERIZATION OF RESINIFERATOXIN BINDING-SITES ON SENSORY NEURONS - COREGULATION OF RESINIFERATOXIN BINDING AND CAPSAICIN SENSITIVITY INADULT-RAT DORSAL-ROOT GANGLIA

Binding of [H-3]resiniferatoxin was seen by autoradiography in section s of rat dorsal root ganglia and the superficial dorsal horn of the sp inal cord. Membranes from rat dorsal root ganglia and spinal cord, but not other tissues, had saturable high-affinity binding sites for [H-3 ]resiniferatoxin. A series of capsaicin analogues competed for these s ites. The sites probably correspond to capsaicin receptors. Systemic p retreatment of rats with capsaicin caused loss of capsaicin sensitivit y in sensory neurons and a reduction in binding of resiniferatoxin to rat dorsal root ganglia, measured by binding assays and autoradiograph y. Adult rat dorsal root ganglion neurons cultured without nerve growt h factor also lost their capsaicin-sensitivity and showed reduced resi niferatoxin binding. Therefore, capsaicin responses in sensory neurons may be regulated by nerve growth factor through control of the number of capsaicin receptors.