AN EARLY-STAGE IN SODIUM-CHANNEL CLUSTERING AT DEVELOPING RAT NEUROMUSCULAR-JUNCTIONS

VOLTAGE-GATED sodium channels (VGSCs) are concentrated in the postsyna ptic membrane at the adult rat neuromuscular junction (NMJ). We have u sed immunolabelling to determine the pattern of initial VGSC accumulat ion during development. At birth, but not 3 days before, VGSC labellin g is detectable at the NMJ and in the perijunctional (periJ) membrane but not elsewhere. A much higher density cluster of VGSCs forms at the NMJ itself 1-2 weeks later. If the nerve is cut 2 days after birth, V GSC labelling persists in the periJ region for at least 4 weeks but th e clustering of VGSCs at the NMJ fails to develop. Thus an early, stab le accumulation of VGSCs develops near the NMJ at least a week before high density postsynaptic VGSC clusters form. (C) 1998 Rapid Science L td.