A histochemical study of the distribution of beta-hydroxybutyrate dehydrogenase in developing rat cerebellum

The distribution of beta-hydroxybutyrate dehydrogenase (3-hydroxybutyrate dehydrogenase, EC 1.1.1.30) in the developing rat cerebellum has been determined using a histochemical method. Staining of Purkinje cells, particularly the soma, was seen at all ages examined. Intense staining of the proximal portions of Purkinje dendrites was noted at 8-11 days postnatally, with less prominent staining of Purkinje dendrites and surrounding structures of the molecular layer seen at later times. Development of glomeruli in the granule cell layer could also be observed due to the intense staining of these structures. (Although noncerebellar structures were not the focus of this study, intense staining of the choroid plexus of the fourth ventricle was also noted.) the transient external germinal layer of the cerebellum did not show appreciable staining. Since beta-hydroxybutyrate dehydrogenase is required for ketone body metabolism, the apparent low level of this enzyme in the external germinal layer suggests that the cells of this layer are not particularly well adapted for utilization of ketone bodies. Thus these results do not provide support for the suggestion that ketone bodies may serve as major substrates for energy metabolism in the external germinal layer of the developing cerebellum. Indeed, the rather restricted distribution of this enzyme in both developing and mature cerebellum (and presumably elsewhere in brain) suggests that ketone body metabolism may be largely confined to relatively few specific cellular compartments.