title: Nicotinic acetylcholine receptors (nAChRs) at zebrafish red and white muscle show different properties during development.
abstract: Nicotinic acetylcholine receptors (nAChRs) are highly expressed at the vertebrate neuromuscular junction (NMJ) where they are required for muscle activation. Understanding the factors that underlie NMJ development is critical for a full understanding of muscle function. In this study we performed whole cell and outside-out patch clamp recordings, and single-cell RT-qPCR from zebrafish red and white muscle to examine the properties of nAChRs during the first 5 days of development. In red fibers miniature endplate currents (mEPCs) exhibit single exponential time courses at 1.5 days postfertilization (dpf) and double exponential time courses from 2 dpf onwards. In white fibers, mEPCs decay relatively slowly, with a single exponential component at 1.5 dpf. By 2 and 3 dpf, mEPC kinetics speed up, and decay with a double exponential component, and by 4 dpf the exponential decay reverts back to a single component. Single channel recordings confirm the presence of two main conductance classes of nAChRs (∼45 pS and ∼65 pS) in red fibers with multiple time courses. Two main conductance classes are also present in white fibers (∼55 pS and ∼73 pS), but they exhibit shorter mean open times by 5 dpf compared with red muscle. RT-qPCR of mRNA for nicotinic receptor subunits supports a switch from γ to ε subunits in white fibers but not in red. Our findings provide a developmental profile of mEPC properties from red and white fibers in embryonic and larval zebrafish, and reveal previously unknown differences between the NMJs of these muscle fibers.© 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 916-936, 2016.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Kazi T
authors.initials: KT
authors.lastname: Ahmed
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.|Department of Physiology, University of Alberta, Edmonton, Alberta, Canada.|Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Declan W
authors.initials: DW
authors.lastname: Ali
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology*; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D011978:Receptors, Nicotinic / Q000502:physiology*; D013997:Time Factors; D015027:Zebrafish
chemical_list: D011978:Receptors, Nicotinic
keywords: NMJ; acetylcholine; muscle; retinal development; zebrafish