The neonatal development of benzodiazepine receptor subtypes in the rat cerebral cortex and cerebellum.

The development of benzodiazepine receptor subtypes in the rat cerebral cortex and cerebellum was studied. The proportions of Type I (CL218872 sensitive binding sites) and Type II (CL218872 insensitive binding sites) in both regions of the neonatal brain were quite different from those of adult. In one day old rat cortex and cerebellum, about 95% of the benzodiazepine receptor were Type II receptor, while these receptors comprised about 50% and 15% of the total in the adult cortex and cerebellum, respectively. From 21 days onward, these ratios in both brain regions did not significantly change through adult age (over 55 days old). The proportion of receptor subtypes in the 21 day cortex (50% type I, 50% type II) was approximately equivalent to that seen in the cerebellum at the 9th day of age. The 3H-flunitrazepam specific binding sites in both brain regions increased markedly after birth, although Type II receptor binding sites did not show any notable gain. Type II receptor specific binding sites in the cortex were not significantly different between neonatal and adult, while these sites in the cerebellum to decrease after birth. These results suggest that Type I and Type II receptors seemed to develop independently during their embryogenesis.