Modulation of acetylcholine receptor channel kinetics by hydrocortisone.
The kinetics of the nicotinic acetylcholine receptor (AChR) channel were analysed in the presence of hydrocortisone (HC, 100-400 microM), an electrically neutral steroid. The channel open time decreased, and in contrast to control conditions did not show any voltage dependency. However, HC induced a new (blocked) component in the closed time distribution, with a time constant that decreased with membrane hyperpolarization. HC decreased also, in a concentration-dependent way, the open time per burst. After coupling HC to bovine serum albumin, to restrict the place of steroid action at the external surface of the membrane, a voltage dependency of steroid action persisted. The effects of HC on the open and blocked time constants did not depend on agonist concentration, but was dependent on the type of agonist used (acetylcholine or nicotine). These results support the hypothesis that HC molecules bind near the agonist binding site.
Nurowska
Ewa
E
Department of Physiology and Pathology and B.R.A.I.N. Centre for Neuroscience, University of Trieste, via Fleming 22, I-34127 Trieste, Italy. nurowska@delta.sggw.waw.pl
Ruzzier
Fabio
F
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002460:Cell Line; D006854:Hydrocortisone / Q000494:pharmacology*; D008564:Membrane Potentials; D051379:Mice; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism*; D012710:Serum Albumin, Bovine
D011978:Receptors, Nicotinic; D012710:Serum Albumin, Bovine; D009538:Nicotine; D000109:Acetylcholine; D006854:Hydrocortisone