Journal of Neuroscience, Vol 9, 1621-1627, Copyright © 1989 by Society for Neuroscience
Selective elimination of cross-compartmental innervation in rat lateral gastrocnemius muscle
SP Donahue and AW English
Department of Anatomy and Cell Biology, Yerkes Regional Primate Research Center, Atlanta, Georgia 30322.
The calf muscles of the rat hindlimb are composed of smaller entities,
called neuromuscular compartments, which are the territories of muscle
innervated by a single, naturally occurring primary (first-order) muscle
nerve branch. While it is quite clear that a precise connectivity exists
very early in development between motoneuron pools and individual muscles,
the mechanisms responsible for producing the adult pattern of compartmental
innervation are unknown. This study uses intracellular recording techniques
to demonstrate that neuromuscular compartments are essentially established
at birth and that postnatal synapse elimination has little role in
establishing neuromuscular compartments. Our results demonstrate the
existence of a small number of cross-compartmental connections in neonates
which are not present in adults. Examining the removal of these
cross-compartmental connections in both normal muscles and in muscles that
have had synapse elimination delayed by tenotomy reveals that the synapses
responsible for this innervation are eliminated in a selective manner.