LAUSR

Carbon‐13 NMR spectroscopy (13C MRS) offers the unique capability to measure brain metabolic rates in vivo. Hyperpolarized 13C reduces the time required to assess brain metabolism from hours to minutes when compared with conventional 13C MRS. This study investigates metabolism of hyperpolarized [1‐13C]pyruvate and [2‐13C]pyruvate in the rat brain in vivo under various anesthetics: pentobarbital, isoflurane, α‐chloralose, and morphine. The apparent metabolic rate from pyruvate to lactate modeled using time courses obtained after injection of hyperpolarized [1‐13C]pyruvate was significantly greater for isoflurane than for all other anesthetic conditions, and significantly greater for morphine than for α‐chloralose. The apparent metabolic rate from pyruvate to bicarbonate was significantly greater for morphine than for all other anesthetic conditions, and significantly lower for pentobarbital than for α‐chloralose. Results show that relative TCA cycle rates determined from hyperpolarized 13C data are consistent with rates previously measured using conventional 13C MRS under similar anesthetic conditions, and that using morphine for sedation greatly improves detection of downstream metabolic products compared with other anesthetics.