Activation of heteroliganded mouse muscle nicotinic receptors.
The activation of the mouse muscle-type nicotinic acetylcholine receptor was studied in the presence of carbachol, and in the simultaneous presence of carbachol and choline. The channel currents were recorded under steady-state conditions using cell-attached single-channel patch clamp, and during transient exposures to the agonists using a piezo-driven fast application system. The presence of choline resulted in inhibition of currents elicited by carbachol. The inhibitory effect of choline manifested as a reduction in the effective opening rate (increase in the mean intracluster closed time duration) in single-channel recordings. In the fast application experiments, the peak current amplitude was reduced and the current rise time increased when choline was co-applied with carbachol. The data were analysed according to a model in which receptor interactions with carbachol and choline resulted in three types of ligation: receptors occupied by two carbachol molecules, receptors occupied by two choline molecules, and receptors in which one agonist binding site was occupied by carbachol and the other by choline, i.e. heteroliganded receptors. All three agonist-bound receptor populations could open albeit with different efficacies. The affinity of the resting receptor to choline was estimated to be 1-2 mm, and heteroliganded receptors opened with an opening rate constant of approximately 3000 s(-1). The results of the analysis suggest that the presence of choline in the neuromuscular junction in vivo has little effect on the time course of synaptic currents. Nevertheless, the contribution of heteroliganded receptors should be taken into consideration when the receptor is exposed simultaneously to two or more agonists.
Akk
Gustav
G
Department of Anesthesiology, Washington University, Campus Box 8054, 660 S. Euclid Ave, St Louis, MO 63110, USA. akk@morpheus.wustl.edu
Milescu
Lorin S
LS
Heckmann
Manfred
M
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002794:Choline / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008024:Ligands; D051379:Mice; D032342:Muscle Cells / Q000187:drug effects / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000187:drug effects / Q000378:metabolism*; D018722:Nicotinic Agonists / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000378:metabolism*
D008024:Ligands; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D002217:Carbachol; D002794:Choline
J Gen Physiol. 2002 Sep;120(3):369-93
12198092
J Pharmacol Exp Ther. 2002 Sep;302(3):1246-52
12183686
J Neurobiol. 2002 Dec;53(4):479-500
12436414
J Neurophysiol. 2003 Apr;89(4):1797-806
12611953
J Pharmacol Exp Ther. 2003 Jun;305(3):1132-41
12626641
J Physiol. 2003 Aug 15;551(Pt 1):155-68
12824448
Ann N Y Acad Sci. 2003 Sep;998:41-52
14592862
J Physiol. 2003 Dec 15;553(Pt 3):857-71
14555718
J Physiol. 1972 May;223(1):173-97
5046143
J Physiol. 1976 Sep;260(3):531-52
10432
Proc R Soc Lond B Biol Sci. 1977 Nov 14;199(1135):231-62
22856
J Physiol. 1978 Apr;277:153-76
306437
Nature. 1980 Jul 3;286(5768):71-3
6248795
Pflugers Arch. 1981 Aug;391(2):85-100
6270629
Biophys J. 1984 Aug;46(2):277-83
6478036
Proc R Soc Lond B Biol Sci. 1985 Sep 23;225(1240):329-55
2414779
J Physiol. 1985 Dec;369:501-57
2419552
Brain Res. 1986 Jun 18;376(1):199-203
3719368
J Mol Biol. 1990 Aug 5;214(3):613-7
2388258
Biophys J. 1991 Aug;60(2):424-32
1717017
Synapse. 1993 Jan;13(1):57-62
7678947
Biophys J. 1993 Feb;64(2):339-56
7681332
J Pharmacol Exp Ther. 1993 Jun;265(3):1474-91
8510023
Mol Pharmacol. 1996 May;49(5):938-47
8622644
J Physiol. 1996 Apr 1;492 ( Pt 1):107-14
8730587
Biophys J. 1996 Jun;70(6):2652-8
8744302
Biophys J. 1996 Jan;70(1):264-80
8770203
J Physiol. 1996 Jul 1;494 ( Pt 1):155-70
8814613
Hum Mol Genet. 1997 May;6(5):767-74
9158151
J Gen Physiol. 1997 Jun;109(6):757-66
9222901
Am J Clin Nutr. 1997 Sep;66(3):622-5
9280183
J Physiol. 1998 Jan 1;506 ( Pt 1):53-72
9481672
J Gen Physiol. 1998 Aug;112(2):181-97
9689026
Biophys J. 1998 Oct;75(4):1817-27
9746523
J Physiol. 1999 Apr 15;516 ( Pt 2):315-30
10087333
J Neurosci. 2005 Feb 23;25(8):1992-2001
15728839
Biophys J. 2005 Apr;88(4):2494-515
15681642
Proc Natl Acad Sci U S A. 1999 Aug 31;96(18):10466-71
10468632
J Neurosci. 1995 Jan;15(1 Pt 1):230-40
7529826
Eur J Pharmacol. 1994 Oct 13;264(1):27-32
7530203
Science. 1995 Apr 14;268(5208):307-10
7716527
Eur J Pharmacol. 1995 Aug 15;290(3):207-19
7589215
Mol Pharmacol. 1996 Jan;49(1):1-6
8569694
Br J Pharmacol. 1999 Dec;128(7):1467-76
10602325
Eur J Pharmacol. 2000 Mar 30;393(1-3):209-14
10771015
Behav Brain Res. 2000 Aug;113(1-2):199-206
10942046
J Physiol. 2000 Sep 15;527 Pt 3:405-17
10990529
J Neurochem. 2000 Dec;75(6):2492-500
11080202
J Physiol. 2002 Nov 1;544(Pt 3):695-705
12411516