Study of frog sartorius muscle acetylcholine receptor using the irreversible inhibitor TDF

The response of normal and denervated frog sartorius muscles to several agonists differing in intrinsic activity was studied using the fluid electrode technique. The response to carbamylcholine could be irreversibly blocked by exposure of the muscles top-trimethylammoniumbenzenediazonium difluoroborate (TDF), but the response could be protected from blockage by agonists and antagonists indicating that both TDF and these ligands act at the acetylcholine binding site of the receptor. It is shown that specific reversible binding of the trimethylammonium group of TDF to the receptor plays little or no role in the irreversible reaction of TDF with the receptor, which accounts for the extremely low specificity of its reaction with the receptor.