99mTc-HMPAO distribution at SPECT is associated with succinate-cytochrome c reductase (SCR) activity in subjects with psychiatric disorders

The origin of altered 99mTc-HMPAO distribution at SPECT in psychiatric disorders is unknown. Correlations between brain 99m Tc-HMPAO distribution and muscle succinate-cytochrome c reductase (SCR, complex II III) were assessed in 20 unmedicated psychiatric patients. Significant negative correlations were found between 99mTc-HMPAO distribution in associative sensory regions and SCR activity. Sensory cortices are normally enriched in complex II activity. The production of electrons and reactive oxygen species affecting the redox state is considered to be highest from complex III, but complex II may also contribute. The negative relationship between 99mTc-HMPAO uptake and SCR activity may be due to redox state alterations influencing fixation of the radiopharmaceutical.