Changes in mRNA Expression of Nicotinic Acetylcholine Receptor Subunits during Embryonic Development of Mouse Masseter Muscle

Nicotinic acetylcholine receptors (nAChRs) switch from the embryonic-type (α2βγδ subunits) to the adult-type (α2βεδ subunits), and disappear besides the neuromuscular junctions with the development of trunk and limb skeletal muscles. However, little is known about this process during the embryonic development of masseter muscle. To identify the time course of the nAChR transition from embryonic day (E) 11 to the newborn stage in mouse masseter muscle, we analyzed the expression level of δ, ε, and γ subunit mRNAs by competitive polymerase chain reaction in combination with reverse transcription as well as distribution of δ subunit protein by immunohistochemistry. The nAChR δ subunit mRNA was initially detected at E11, showed an approximately 25-fold increase (p