title: Development alters the expression of calcium currents in chick limb motoneurons.
abstract: Calcium current types expressed in vertebrate spinal motoneurons have not been previously resolved. We have resolved three types in chick limb motoneurons identified by retrograde labeling and report that dramatic changes in their expression take place during development in vivo. T-, N-, and L-type calcium currents were distinguished on the basis of kinetics, voltage dependence, and unique pharmacological sensitivities. Developmental changes were characterized by studying motoneurons isolated from embryos at three stages spanning neuromuscular system development. T currents were dominant at the earliest stage. Motoneurons from embryos 2 days older showed much reduced T currents and much increased N and L currents. We suggest that mature motoneurons will be dominated by N- and L-type calcium currents and that T current may serve developmental roles.
authors.affiliation: Department of Physiology, Colorado State University, Fort Collins 80523.
authors.forename: D P
authors.initials: DP
authors.lastname: McCobb
authors.forename: P M
authors.initials: PM
authors.lastname: Best
authors.forename: K G
authors.initials: KG
authors.lastname: Beam
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D005314:Embryonic and Fetal Development; D006614:Hindlimb / Q000196:embryology* / Q000294:innervation; D015640:Ion Channel Gating / Q000187:drug effects; D009046:Motor Neurons / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D000584:Amiloride; D014700:Verapamil; D002118:Calcium