The Development of Nerve-muscle Junctions in Monolayer Cultures of Embryonic Spinal Cord and Skeletal Muscle Cells

Most of the previous work on the formation of nerve-muscle connections has been done either in whole embryos (1-3) or in organ cultures of tissue fragments (4, 5) . As a step towards studying innervation mechanisms at the level of single cell interactions we have recently determined that neuromuscular junctions can develop in monolayer cultures of mixed spinal cord and skeletal muscle cells from chick embryos (6) . The present report extends these observations to longer term cultures of these cells and presents evidence suggestive of the formation, in such cultures, of twitch-type ("en plaque") nerve-muscle contacts, in addition to the bulbous nerve endings ("en grappe") described in the previous report .