Nicotinic currents of cultured rat superior cervical ganglion neurons and use-dependent block by mecamylamine
Abstract
AIM:
Comparison of action of nicotinic agonists and antagonists on nicotinic acetylcholine receptor (nAChR) in superior cervical ganglion (SCG) neurons.
METHODS:
Whole-cell recordings were made from cultured neonatal rat SCG neurons. Cholinergic drugs were applied by local pressure perfusion.
RESULTS:
The neurons were activated by nicotinic agonists 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 mecamylamine (Mec), hexamethonium and curare, the efficacies were 435 +/- 154 pA, 725 +/- 320 pA, 887 +/- 214 pA, but not by alpha-bungarotoxin. The block by Mec was use-dependent, i.e., it was dependent on repeated presentation of the agonists. The first 6 peak currents were expressed as percentage of the first response as following: 100, 64 +/- 3, 50 +/- 3, 41 +/- 4, 32 +/- 3%.
CONCLUSION:
The present data suggest that nAChR of SCG neurons have different pharmacological characteristics from that of muscle or central neurons.
Keywords:
Comparison of action of nicotinic agonists and antagonists on nicotinic acetylcholine receptor (nAChR) in superior cervical ganglion (SCG) neurons.
METHODS:
Whole-cell recordings were made from cultured neonatal rat SCG neurons. Cholinergic drugs were applied by local pressure perfusion.
RESULTS:
The neurons were activated by nicotinic agonists 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 mecamylamine (Mec), hexamethonium and curare, the efficacies were 435 +/- 154 pA, 725 +/- 320 pA, 887 +/- 214 pA, but not by alpha-bungarotoxin. The block by Mec was use-dependent, i.e., it was dependent on repeated presentation of the agonists. The first 6 peak currents were expressed as percentage of the first response as following: 100, 64 +/- 3, 50 +/- 3, 41 +/- 4, 32 +/- 3%.
CONCLUSION:
The present data suggest that nAChR of SCG neurons have different pharmacological characteristics from that of muscle or central neurons.