Sensory stimulation induces local cerebral glycogenolysis: Demonstration by autoradiography

Brain glycogen stores are localized primarily to glia and undergo continuous utilization and resynthesis. To study the function of glycogen under normal conditions in brain, we developed an autoradiographic method of demonstrating local glycogen utilization in the awake rat. The method employs labeling of brain glycogen with ¹⁴C(3, 4)glucose, in situ microwave fixation of brain metabolism, and anhydrous tissue preparation. With this technique, tactile stimulation of the rat face and vibrissae was found to accelerate the utilization of labeled glycogen in brain regions known to receive sensory input from face and vibrissae: the contralateral somatosensory cortex and the ipsilateral trigeminal, sensory and motor nuclei. These findings demonstrate a link between neuronal activity and local glycogen utilization in mammalian brain and suggest that, like other tissues, brain may respond to sudden increases in energy demand in part by rapid glycolytic metabolism of glycogen. As cerebral glycogen is restricted primarily to glia, these observations also support a close coupling of glial energy metabolism with neuronal activity.