DENDRITIC DEVELOPMENT IN NORMAL LUMBAR MOTONEURONS AND FOLLOWING NEONATAL NERVE CRUSH IN THE RAT

Motoneurons from the rat were retrogradely labelled with cholera toxin -horseradish peroxidase at intervals during normal postnatal developme nt and following nerve crush at birth. Normal cells displayed a relati vely steady increase in total visible dendritic density which was larg ely confined to the dorsomedial direction. After nerve crush at birth, dorsomedially orientated dendrites failed to achieve normal density, resulting in a significantly smaller dendritic tree by adulthood. Ther e was also a transient, abnormal extension of dendrites in the mediove ntral direction which had regressed to normal levels by maturity. The predominance of changes in the dorsally directed region of the dendrit ic tree suggests that dendritic development of motoneurons is influenc ed by synaptic inputs in the dorsal horn.