Distribution and postnatal changes of aromatase mRNA in the female rat brain

Distribution and postnatal changes of aromatase mRNA in the Wistar strain female rats brain were investigated to elucidate the mechanism of the region-specific and stage-related regulations of brain aromatase activity. Total RNAs extracted from the hypothalamus-preoptic area (HPOA), amygdala, cerebral cortex, cerebellum and anterior hypophysis were subjected to a quantitative reverse transcription-polymerase chain reaction-Southern blotting (RT-PCR-SB) assay. The levels of aromatase mRNA were as follows: amygdala > cerebral cortex not equal to HPOA >> cerebellum not equal to anterior hypophysis. These results roughly paralleled the distribution of the aromatase activity and the aromatase protein reported previously, with the exception of that of the cerebral cortex. The postnatal developmental patterns of aromatase mRNA in the HPOA and cerebral cortex were further studied. The levels of aromatase mRNA in the HPOA tended to be high around birth (day 0) and to decrease at days 4-8 followed by no remarkable change to an adult. The developmental pattern in the HPOA was essentially similar to that of aromatase activity. On the other hand, in the cerebral cortex where very low or no aromatase activity was reported throughout developmental stages, aromatase mRNA was low but detectable level around day 0, thereafter gradually increased to an adult level. From these results, it is inferred that synthesis of the aromatase protein by the level of the mRNA seems to mainly regulate the aromatase activity in a region-specific and stage-related fashion in most parts of the rat brain, except for the cerebral cortex where the posttranscriptional regulation may play an important role.