Muscarinic acetylcholine responses in the early embryonic chic retina
Article first published online: 11 OCT 2004
Copyright © 1994 John Wiley & Sons, Inc.
Journal of Neurobiology
Volume 25, Issue 9, pages 1144–1153, September 1994
How to Cite
Yamashita, M., Yoshimoto, Y. and Fukada, Y. (1994), Muscarinic acetylcholine responses in the early embryonic chic retina. J. Neurobiol., 25: 1144–1153. doi: 10.1002/neu.480250909
- Issue published online: 11 OCT 2004
- Article first published online: 11 OCT 2004
- Manuscript Accepted: 9 MAY 1994
- Manuscript Received: 27 JAN 1994
- muscarinic receptor;
- Ca2+ mobilization;
- chick embryo
The action of acetylcholine on cytoplasmic Ca2+ concentration ([Ca2+]i) was studied in early embryonic chick retinae. Whole neural retinae were isolated from embryonic day 3 (E3) chicks and loaded with a Ca2+-sensitive fluorescent dye (Fura-2). Increases in [Ca2+]i were evoked by the puff application of acetylcholine at concentration than 0.1 μM. The Ca2+ response became larger in dose–dependant manner up to 10 μM of acetylcholine applied. The rise in [Ca2+]i was not due to the influx of Ca+2 through calcium channels, but to the release of Ca2+ from internal stores. A calcium channel antagonist, nifedipine, which completely blocks the Ca2+ rise caused by depolarization with 100 mM K+, had no effects on the acetylcholine response and the Ca2+ response to acetylcholine occurred even in a Ca2+-free medium. The Ca2+ response to acetylcholine was mediated by muscarinic receptors. Atropine of 1 μM abolished the response to 10 μM acetylcholine, whereas d-tubocurarine of 100 μM had no effects. Two muscarinic agonists, muscarine and carbamylcholine (100 μM each), evoked comparable responses with that to 10 μM acetylcholine. The developmental change of the muscarinic response was examined from E3 to E13. The Ca2+ response to 100 μM carbamylcholine was intense at E3-E5, then rapidly declined until E8. The muscarinic Ca2+ mobilization we found in the early embryonic chick retina may be regarded as a part of the “embryonic muscarinic system” proposed by Drew's group, which appears transiently and ubiquitously at early embryonic stages in relation to organogenesis. 1994 John Wiley & Sons, Inc.