Effect of glial metabolism inhibition upon retention of 99mTc-HMPAO in rat brain

In order to clarify whether inhibition of glial TCA cycle alters the retention of 99mTc-hexamethyl propylene amine oxime (HMPAO), a dual tracer autographic study was performed using 99mTc-HMPAO and N-isopropyl-14C-para-iodo amphetamine (14C-IMP) in rats infused with fluorocitrate. 99mTc-HMPAO (74 MBq) combined with 14C-IMP (185 kBq) were intravenously injected into rats at 4 hours after the microinjection of fluorocitrate (1 nmol/μL, 2 μL) into the right striatum. Rats were decapitated at 5 minutes after the injection radiotracers, then autoradiograms for 99mTc-HMPAO were obtained. After the decay of 99mTc, the same brain slices were re-contacted with imaging plate, and autoradiograms for 14C-IMP were made. Significant increases in either 99mTc-HMPAO or 14C-IMP in the right striatum (fluorocitrate infused area) with almost the same degree were obtained, which strongly suggested that inhibition of glial metabolism dose not alter retention of 99mTc-HMPAO. In addition, a correlation of radioactivity concentration between 99mTc-HMPAO and 14C-IMP either in normal region or region infused with fluorocitrate was seen in each rat brain. These results indicated the validity of the dual tracer autoradiography with 99mTc-HMPAO and 14C-IMP to investigate response of local cerebral blood flow in various kinds of animal models. (author)