Permanent alterations in the rat spinal cord following prenatal exposure to N-ethyl-N-nitrosourea

Pregnant rats between gestational stages E14-E22 were given a single injection of N-ethyl-N-nitrosourea (ENU). Pups born of these females were sacrificed 60 days after birth and their spinal cords examined qualitatively and quantitatively. Quantitative analysis involved measurement of spinal cord length and volume, estimation of neuron number, and the measurement of individual cell dendritic number and length. Cytoarchitecturally spinal cords appeared normal in all animals regardless of the age when they were exposed to ENU. Animals exposed during the latter portion of neurogenesis in the spinal cord (E14-E16) had significantly (p less than 0.05) reduced volumes of gray matter and reduced cell counts. Cellular analysis showed that all animals exhibited some stunting of dendritic length, although the number of dendritic branches was significantly (p less than 0.01) higher than normal for neurons of the intermediate gray and the substantia gelatinosa. Increase in the number of dendrites per cell suggests a mechanism of structural compensation by the surviving neuronal cells following their exposure to the teratogen.