Rate of cerebral energy consumption in concussive head injury in the rat.

The metabolic rate was determined in the rat brain during the immediate concussive response to standardized impact accelerations of 7 and 9 m/sec velocity. In one series, the metabolic state was determined in freeze-clamped cortical and brain-stem tissue 20 seconds after the impact. The metabolic rate was calculated from the rate of energy depletion in the adjacent unclamped tissue during 10 seconds of total ischemia. The freeze-clamping procedure per se was shown to enhance the metabolic rate probably by inducing mechanical excitation. In another series, in situ freezing was used for tissue sampling in the same situation. A 10-second period of heart standstill induced a standardized period of ischemia. During the acute concussive response to impact acceleration at 7 m/sec velocity, there was an increase of the metabolic rate in the brain stem. A more intense concussive impact at 9 m/sec velocity further enhanced this reaction and also involved the cortex. It is concluded that the basis of the immediate concussive response is a mechanically elicited neuronal excitation. This may lead to energy depletion unless the increased metabolic demands are met.