ALTERATIONS IN BRAIN-STEM AND CORTICAL ORGANIZATION OF RATS SUSTAINING PRENATAL VIBRISSA FOLLICLE LESIONS

Vibrissa follicles were cauterized in late fetal or newborn rats to de termine whether the relationships between brainstem and cortical chang es observed after neonatal peripheral damage would also be obtained wh en vibrissa follicles were cauterized earlier in development. Vibrissa follicles were cauterized between embryonic day 15 (E-15) and die day of birth (P-0). The vibrissa-related representation in the brainstem was examined with cytochrome oxidase histochemistry, and that in the c ortex was evaluated with either serotonin immunocytochemistry or anter ograde labeling with Di-I when animals reached 6-8 days of age. There was a significant relationship between the ages at which lesions were carried out and the extent to which the representations of undamaged v ibrissa follicles were altered in the brainstem and cortex. Peripheral lesions carried out between E-15 and E-18 resulted in significant inc reases in the cross-sectional areas of the patches corresponding to th e undamaged vibrissa follicles in both the brainstem and cortex. Lesio ns at later ages resulted in significant increases only in the cortex. In some animals that sustained peripheral damage on E-20 and all of t hose that received lesions on P-0, there were aggregates of labeling i n cortex that had no counterpart in the brainstem. Prenatal, but not p ostnatal, vibrissa follicle damage also reduced the overall dimensions of the cortical region devoted to the representation of these recepto r organelles. Finally, there was a strong negative correlation between the magnitude of peripheral lesions (i.e., the number of vibrissa fol licles ablated) and the extent of the reorganization in the brainstem and cortex.