Peripheral sensory stimulation and the release of transmitter amino acids in vivo from specific regions of cerebral cortex.

The effects of sensory stimulation on the release of amino acids from sensorimotor and visual cortex have been studied using a superfusion technique. Electrical stimulation of the brachial plexus contralateral to the superfusion cannula increased significantly the release of glutamate and glutamine from the sensorimotor cortex of anaesthetized rats. No clear effect was observed with the other amino acids. Stimulation of the ipsilateral plexus had no effect on glutamate and glutamine release. In unanaesthetized animals stimulation of the contralateral brachial plexus raised the levels of all the amino acids in sensorimotor cortex superfusate. Weak photic stimulation of the eyes of dark-adapted rats increased glutamate release from the visual cortex but caused no significant change in the release of other amino acids. All evoked increases in amino acids release were reversible at the cessation of the stimuli.