Pentobarbital Anesthesia Reduces Blood–Brain Glucose Transfer in the Rat

Abstract: Pentobarbital anesthesia (40 mg kg^–1) was accompanied by a 50% decrease of blood flow and a 40% decrease of unidirectional blood‐brain glucose transfer in the parietal cortex of the rat brain. The correlation was explained by a decrease of the number of perfused capillaries. The maximal transport capacity, T_max, decreased from 409 to 235 μ mol 100 g^–1 min^–1 and the half‐saturation constant, K_m, from 8.8 to 4.9 mm. At 8.3–8.7 mm‐glucose in arterial plasma, the transfer constant (clearance) for unidirectional blood‐brain transfer decreased from 0.195 ± 0.011 in awake rats to 0.132 ± 0.005 ml g^–1 min^–1 in anesthetized rats. Half of the decrease was due to less complete diffusion‐limitation of glucose uptake at the low plasma flow rate in brain, the other half to the decreased T_max.