GAP-43 EXPRESSION IN THE MEDULLA OF MACAQUE MONKEYS - CHANGES DURING POSTNATAL-DEVELOPMENT AND THE EFFECTS OF EARLY MEDIAN NERVE REPAIR

Expression of GAP-43, a neuronal specific growth associated phosphopro tein, has been highly correlated with the growth and remodeling of the nervous system during development and regeneration. As part of an eff ort to understand mechanisms of developmental plasticity in the somato sensory system, we determined how the expression of GAP-43 is affected by prenatal and early postnatal nerve cut and repair in macaque monke ys. We also observed normal developmental changes in the expression of GAP-43 during early postnatal life in macaque monkeys. The normal cun eate nucleus, as well as other nuclei of the ascending somatosensory p athways, had low levels of GAP-43 at birth that increased by 3 months and declined thereafter to reach adult levels between 8 and 15 months of age. Fiber tracts expressed low levels of GAP-43 at all postnatal a ges, except the pyramidal tract which demonstrated high levels at birt h that decreased over the first year. These observations suggest a gra dual but differential synaptic maturation in lower brain stem nuclei a s macaque monkeys mature. Greatly increased levels of GAP-43 were obse rved at the time of birth in the cuneate nucleus of two macaque monkey s with prenatal (E94 and E114) nerve repair. Such an increase was not found after prenatal nerve repair with a postnatal survival time of 15 months, or after early postnatal nerve repair with short (80 days) or long (20 months) survivals. The results suggest that reorganization m echanisms at central terminals of peripheral nerves are very different following prenatal than postnatal nerve damage.