Evidence of muscarinic acetylcholine receptors in the retinal centrifugal system of the chick

Abstract

In this study we characterize the presence of muscarinic acetylcholine receptors (mAChR) in the isthmo-optic nucleus (ION) of chicks by immunohistochemistry with the M35 antibody. Some M35-immunoreactive fibers were observed emerging from the retinal optic nerve insertion, suggesting that they could be centrifugal fibers. Indeed, intraocular injections of cholera toxin B (CTb), a retrograde tracer, and double-labeling with M35 and CTb in the ION confirmed this hypothesis. The presence of M35-immunoreactive cells and the possible mAChR expression in ION and ectopic neuron cells in the chick brain strongly suggest the existence of such a cholinergic system in this nucleus and that acetylcholine release from amacrine cells may mediate interactions between retinal cells and ION terminals.

Ca2+-Mobilization and Cell Contraction after Muscarinic Cholinergic Stimulation of the Chick Embryo Lens

“…15 The presence of mAChRs has been demonstrated by M35 immunohistochemistry and Western blot during ecdysone-induced morphogenesis of an epithelial cell line from Chironomus tentans 17 and by M35 immunohistochemistry in the isthmo-optic nucleus of the chick embryo. 18 Comparison of M35 immunohistochemistry and autoradiogra- 19 Taking all these results together, we conclude that binding of M35 reliably identifies muscarinic receptor expression in embryonic tissues. The subtype-specific polyclonal antibodies of Ndoye et al 13 are directed against the carboxyl termini of the receptor protein.…”

Identification of neurons with acetilcholinesterase and NADPH-diaphorase activities in the centrifugal visual system of the chick

“…According to this idea, the optic tectum layer, which projects to the ION and Ecn, would be ChAT positive (Sorenson et al, 1989;Bagnoli et al, 1992). In addition, CVS cells, which probably receive this cholinergic input, present both nicotinic and muscarinic acetylcholine receptors (Nickla et al, 1994;Calaza and Gardino, 2000). Therefore, the co-localization of CTb immunolabeling and AchE activity corroborates the idea that CVS cells could be part of the cholinergic system in the chick.…”

“…The experimental procedures were as described previously (Calaza and Gardino, 2000). Briefly, the animals (n = 8), ranged in age from 7 to 10 days post-hatched, were first anaesthetized with ether, and then a topic anesthetic (Anestalcon) was applied to the cornea.…”

“…A survival period of 5-7 days was allowed for retrograde transport of the cholera toxin to occur reaching the CVS (Mikkelsen, 1992). No histological differences in CTb labeling were observed in chick brain using this survival time as described previously (Calaza and Gardino, 2000). The ipsilateral hemisphere was used as control for CTb transport, since few if any ganglion cell axons in the chick retina project to the ipsilateral optic tectum (Crossland et al, 1974).…”

“…Some studies suggest that CVS consists of cholinoceptive cells. Indeed, ION and Ecn cells express both muscarinic and nicotinic acetylcholine receptors (Nickla et al, 1994;Calaza and Gardino, 2000). No choline acetyltransferase (ChAT) immunoreactivity has been demonstrated in ION of the chicken (Sorenson et al, 1989) suggesting it might be produced by the optic tectum.…”