Improvement in Local Cerebral Blood Flow Measurement in Gerbil Brains by Prevention of Postmortem Diffusion of [ 14 C]Iodoantipyrine

Postmortem diffusion of [¹⁴C]iodoantipyrine, which distorts the image of cerebral blood flow, can occur in at least three steps; from decapitation until the brain is frozen, while frozen sections on coverslips are thawed, and when dried sections are applied to x-ray film. In the present study, the first two steps were modified to reduce the time during which brain tissue was wet. When the brains of gerbils were taken out of the skulls and immersed in chilled isopentane (–45°C), 90–95 s elapsed between decapitation until the brain tissues were frozen. However, immersion of whole heads in liquid nitrogen after decapitation decreased the time to 25 s. The autoradiograms had better contrast after the freezing procedure with liquid nitrogen than after that with chilled isopentane. The drying time of the thawed sections was markedly reduced by blowing hot air across the sections on a hot plate, and this resulted in clearer images on autoradiograms. In most of the tissues with values of cerebral blood flow over 100 ml 100 g⁻¹ min⁻¹ as measured using the conventional drying method, the corresponding values were higher if the modified method was used. In contrast, in tissues with values less than 100 ml 100 g⁻¹ min⁻¹, the corresponding values were lower. Moreover, the differences between flows in adjacent small brain structures were less clear if the sections were dried by the conventional method. Reducing the time during which postmortem brains or sections are wet can help prevent [¹⁴C]iodoantipyrine diffusion artifacts.