Imaging mitochondrial complex I activation during a vibrotactile stimulation: A PET study using [ 18 F]BCPP-EF in the conscious monkey brain.

In order to evaluate the capability of 2- tert -butyl-4-chloro-5-{6-[2-(2-[ ¹⁸ F]fluoroethoxy)-ethoxy]-pyridin-3-ylmethoxy}-2H-pyridazin-3-one ([ ¹⁸ F]BCPP-EF), a novel positron emission tomography (PET) probe for mitochondrial complex I (MC-I) activity, to assess neuronal activation, an activation PET study was conducted in the conscious monkey brain with a continuous unilateral vibrotactile stimulation. PET scans with [ ¹⁵ O]H ₂ O, [ ¹⁸ F]BCPP-EF, or 2-deoxy-2-[ ¹⁸ F]fluoroglucose ([ ¹⁸ F]FDG) were conducted under: (1) resting conditions; (2) a continuous vibration stimulation; (3) a continuous vibration stimulation after 15-min pre-vibration; and (4) a continuous vibration stimulation after 30-min pre-vibration. The contralateral/ipsilateral ratio (CIR) in the somatosensory cortex showed significant increases in the uptake of [ ¹⁵ O]H ₂ O, [ ¹⁸ F]BCPP-EF, and [ ¹⁸ F]FDG with the vibration stimulation. The longer pre-vibration duration induced significantly lower CIR in regional cerebral blood flow (rCBF) measured using [ ¹⁵ O]H ₂ O, whereas it did not affect the CIR in [ ¹⁸ F]BCPP-EF or the regional cerebral metabolic rate of glucose (rCMRglc) measured using [ ¹⁸ F]FDG 30-60 min after the injection. These results suggest that the [ ¹⁸ F]BCPP-EF response in the later phase of scans was not influenced by the increase in rCBF, indicating the capability of [ ¹⁸ F]BCPP-EF to detect acute changes in MC-I activity induced by neuronal activation. However, the metabolic shift from glycolysis to oxidation was not observed under the stimulation used here.