Changes in the distribution of peanut agglutinin (PNA) binding molecules during muscle reinnervation following nerve crush injury

Peanut agglutinin (PNA) staining during muscle reinnervation following a cr ushing injury of the sciatic nerve was performed in reference to the neural profiles immunolabeled with the PGP 9.5 antibody. PNA staining in the norm al controls exhibited dots, granules, or lines along the length of the nerv e fibers in the nerve trunk, but was faint or absent in the motor endplate. At seven days post-crush, PNA staining was detected around the vacuolated neural structures in the disorganized nerve trunk, but was still faint or a bsent in the motor endplate. At twenty-one days post-crush, when PGP 9.5-po sitive regenerating axons appeared in most of the motor endplates, PNA stai ning, either faint or strong, followed the pathway of the nerve fibers deli neated by PGP9.5-like immunoreactivity. During reinnervation to the motor e ndplates, PNA staining displayed signs of remodeling in the nerve trunk, su ch as marked variations in density and profile in the nerve fiber-associate d dots or patches; it increased in intensity in the connective tissue cover ing the area of the motor endplate, as well as in the junctional myofiber s urface. The structures recognizable by PNA coincided with components of the connective tissue such as collagen fibers and capillaries. Results suggest that: 1) the expression of PNA-binding molecules is dependent on the state of innervation, and 2) the spatiotemporal relationship between neural prof iles and PNA staining provides sequences of axonal extension and subsequent nerve terminal maturation during regeneration in the motor endplate.