CHARACTERIZATION BY [H-3] RESINIFERATOXIN BINDING OF A HUMAN VANILLOID (CAPSAICIN) RECEPTOR IN POSTMORTEM SPINAL-CORD

Membranes obtained from post-mortem human spinal cord specimens bound [H-3]resiniferatoxin (RTX) with an affinity of 11 nM in a noncooperati ve fashion. This binding behaviour contrasted with the high affinity [ H-3]RTX binding (K-d = 24 pM) to rat spinal cord membranes which displ ayed apparent positive cooperativity (cooperativity index = 1.8) but w as in accord with the low affinity (K-d = 5 nM) non-cooperative RTX bi nding to guinea pig spinal cord preparations. We conclude that the [H- 3]RTX binding assay utilizing post-mortem human spinal cord membranes affords a novel biochemical approach to explore structure-activity rel ations at human vanilloid receptors.