PHYSOSTIGMINE AND ACETYLCHOLINE DIFFERENTIALLY ACTIVATE NICOTINIC RECEPTOR SUBPOPULATIONS IN LOCUSTA-MIGRATORIA NEURONS

Citation
I. Vandenbeukel et al., PHYSOSTIGMINE AND ACETYLCHOLINE DIFFERENTIALLY ACTIVATE NICOTINIC RECEPTOR SUBPOPULATIONS IN LOCUSTA-MIGRATORIA NEURONS, Brain research, 789(2), 1998, pp. 263-273
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences
Journal title
Volume
789
Issue
2
Year of publication
1998
Pages
263 - 273
Database
ISI
SICI code
Abstract
The effects of acetylcholine (ACh) and physostigmine (PHY) on thoracic ganglion neurons of Locusta migratoria were investigated using whole- cell and cell-attached voltage clamp. ACh activated whole-cell current s with variable amplitudes, time course and ion channel block between cells, suggesting differential expression of nicotinic acetylcholine r eceptor (nAChR) subtypes. This was supported by selective block of the peak of the currents by the alpha 7-specific alpha-conotoxin ImI. PHY at 100 mu M evoked smaller whole-cell currents with variable amplitud es and marginal desensitization. The PHY/ACh amplitude ratio varied be tween cells, and was positively related to the time constant of decay of the ACh response. EC50 values for the peak amplitude of the ACh- an d PHY-induced currents were 50 pM and 3 mu M, respectively. Both agoni sts activated nAChR, indicated by equal voltage-dependence and reversa l potentials and the same pharmacological properties of ACh and PHY re sponses. In addition, PHY and ACh induced ion channel block. Co-applic ation and cross-desensitization experiments showed that ACh and PHY ac tivate the same nAChR subpopulations. Both agonists activated nicotini c single channels with three conductance levels, which were equal for ACh and PHY, indicating activation of the same nAChR subtypes by both agonists. However, for all levels PHY displayed a lower open probabili ty than ACh. Taken together, different whole-cell responses appear to originate from differential activation, desensitization and ion channe l block by ACh and PHY of distinct nAChR populations. (C) 1998 Elsevie r Science B.V.