Effect of afferent brachial stimulation and photic stimulation on glycogen concentration in cortical brain tissue

Afferent electrical stimulation (AES) of the brachial plexus caused a 41% increase in glycogen concentration in the contralateral sensory-motor cortex of rat brain. This increase in glycogen concentration was confined to the stimulated sensory-motor cortex; no change in glycogen concentration in adjacent areas, such as visual and frontal cortex was observed. The increase in glycogen concentration was completely reversed within 10 min after cessation of stimuli. Assays of relevant metabolites in the sensory-motor cortex demonstrated an increase in the concentrations of pyruvate and glucose-6-phosphate by 135 and 93%, respectively, and a slight decrease (14%) in the concentration of glucose. No change in the concentration of lactate was found. Photic stimulation of the eyes of dark adapted guinea pigs caused a 13% increase in glycogen concentration in the visual cortex and had no effect on glycogen concentration in other cortical areas. The same photic stimulation had no effect on glycogen concentration in the visual cortex of Sprague-Dawley rats. The results suggest that the increased glycogen concentration in cortical areas results from increased uptake of glucose following stimulation.