Developmental changes in the cerebellar cortex after locus ceruleus lesion with 6-hydroxydopamine in the rat.

Three-day-old rats received an infusion of a small dose of 6-hydroxydopamine (6-OHDA) (12 micrograms) directly into the locus ceruleus nuclei, in order to induce a subtotal lesion of the noradrenergic system. Significant modifications in cerebellum maturation were observed, mainly a regression failure in the perisomatic Purkinje cell processes in the depth of the fissura prima of 10-day-old rats, a reduction in the whole vermis surface area and in the total number of internal granule cells at 15 days of age, the number of external granule cells was slightly enhanced. To discriminate between the effects of the noradrenergic deafferentation and the nonspecific toxic effects of 6-OHDA, these results were compared to those obtained after an infusion of 6-OHDA + bovine serum albumin (BSA) into the locus ceruleus (which produced a selective deafferentation) and after an injection of 6-OHDA directly into the IVth ventricle (which increased the nonspecific toxic effects). Whatever the procedure used, the same reduction in the size of the vermis was observed. However, the fissuration index was not modified when BSA was added to the 6-OHDA solution. We conclude that noradrenergic deafferentation by itself was sufficient to reduce the growth of the cerebellum at certain periods of postnatal life.