Autoradiographic measurement of local cerebral beta-hydroxybutyrate uptake in the rat during postnatal development.

An autoradiographic method has been developed for the regional assessment of cerebral tracer levels after the acute intravenous injection of [3-14C]beta-hydroxybutyrate in developing rats. The animals were studied at five postnatal stages, i.e. postnatal day 10 (P10), P14, P17, P21 and P35. Tracer levels were high from P10 to P17, reaching peak values at P14, which were two- to threefold higher than those at P10. At P17, tracer concentrations were about twice as low as at P14. Between P17 and P21, regional 14C concentrations were again reduced by about twofold in all areas studied and decreased further by about 50% after weaning reaching quite low levels by P35. The distribution of 14C inside sections appeared to be rather homogeneous throughout the brain at all stages studied, never exceeding a ratio higher than 2 at any stage studied. These results are in good agreement with previous data on the rate of uptake and utilization of beta-hydroxybutyrate by the immature rat brain.