Maturation of neuromuscular transmission during early development in zebrafish.
We have examined the rapid development of synaptic transmission at the neuromuscular junction (NMJ) in zebrafish embryos and larvae by patch-clamp recording of spontaneous miniature endplate currents (mEPCs) and single acetylcholine receptor (AChR) channels. Embryonic (24-36 h) mEPCs recorded in vivo were small in amplitude (<50 pA). The rate of mEPCs increased in larvae (3.5-fold increase measured by 6 days), and these mEPCs were mostly of larger amplitude (10-fold on average) with (</=5-fold) faster kinetics. Intracellular labeling with Lucifer yellow indicated extensive coupling between muscle cells in both embryos and larvae (</=10 days). Blocking acetylcholinesterase (AChE) with eserine had no effect on mEPC kinetics in embryos at 1 day and only partially slowed (by approximately 1/2) the decay rate in larvae at 6 days. In acutely dissociated muscle cells, we observed the same two types of AChR with conductances of 45 and 60 pS and with similar, brief (<0.5 ms) mean open times in both embryos and larvae. We conclude that AChR properties are set early during development at these early stages; functional maturation of the NMJ is only partly shaped by expression of AChE and may also depend on postsynaptic AChR clustering and presynaptic maturation.
Nguyen
P V
PV
Centre for Research in Neuroscience, McGill University and Montreal General Hospital Research Institute, Montreal, Quebec H3G 1A4, Canada.
Aniksztejn
L
L
Catarsi
S
S
Drapeau
P
P
D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004558:Electric Stimulation; D004625:Embryo, Nonmammalian; D066298:In Vitro Techniques; D007700:Kinetics; D007814:Larva; D009045:Motor Endplate / Q000254:growth & development / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D009469:Neuromuscular Junction / Q000254:growth & development / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010830:Physostigmine / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology*; D015027:Zebrafish
D002800:Cholinesterase Inhibitors; D011950:Receptors, Cholinergic; D010830:Physostigmine