In vivo regional levels of PGE and thromboxane in mouse brain: Effect of decapitation,focused microwave fixation,and indomethacin

A focused microwave fixation technique was tested for use in determining basal PGE and thromboxane B₂ levels of mouse brain. Focused microwave irradiation (3.5 Kw/0.4 sec) to the head of C3H mice produced basal values of PGE and TXB₂ which were five-fold less than those in animals killed by decapitation. Indomethacin (10 mg/kg) pretreatment blocked the decapitation rise in PGE and TXB₂ levels and gave values similar to focused microwave irradiation. Indomethacin pretreatment combined with microwave fixation did not reduce PG levels more tham microwave treatment alone. When microwave fixation was used, there was no difference in regional (cerebral cortex, whole cerebellum, midbrain, hypothalamus) levels of either PGE or TXB₂. However, PGE levels were significantly higher than TXB₂ in all regions. After decapitation there was a greater increase in TXB₂ than PGE. The cerebellum produced less PGE and TXB₂ after decapitation compared to the other regions. Our results confirm the usefulness of the focused microwave irradiation technique for examining $\text{in vivo}$ basal prostaglandin levels in mouse brain.