NICOTINIC CURRENTS OF CULTURED RAT SUPERI OR CERVICAL-GANGLION NEURONS AND USE-DEPENDENT BLOCK BY MECAMYLAMINE

AIM: Comparison of action of nicotinic agonists and antagonists on nic otinic acetylcholine receptor (nAChR) in superior cervical ganglion (S CG) neurons. METHODS: Whole-cell recordings were made from cultured ne onatal rat SCG neurons. Cholinergic drugs were applied by local pressu re perfusion. RESULTS: The neurons were activated by nicotinic agonist s and peak current were acetylcholine (ACh), 443 +/- 183 pA; nicotine; 1175 +/- 377 pA; dimethylphenylpiperazinium (DMPP), 2946 +/- 358 pA, respectively. The nicotinic responses were blocked by mecamylanine (Me c), hexamethonium and curare, the efficacies were 435 +/- 154 pA, 725 +/- 320 pA, 887 +/- 214 pA, but not by alpha-bungarotoxin. The block b y Mec was use-dependent, ie, it was dependent on repeated presentation of the agonists. The first 6 peak currents were expressed as percenta ge of the first response as following: 100, 64 +/- 3, 50 +/- 3, 41 +/- 4, 36 +/- 4, 32 +/- 3 %. CONCLUSION: The present data suggest that nA ChR of SCG neurons have different pharmacological characteristics from that of muscle or central neurons.