Reversible changes in glutamine levels in the cat cerebral cortex evoked by afferent electrical stimulation and by administration of pentamethylenetetrazole (pentylenetetrazol)

Morphine suppression of neurotransmitter release evoked by sensory stimulation in vivo

The effects of morphine and naloxone on the release of acetylcholine and amino acid neurotransmitters from sensorimotor cortex were studied employing an in vivo superfusion cannula. Morphine (20 mg/kg) reduced the spontaneous release of acetylcholine but had no detectable effect on the spontaneous release of amino acids. It also suppressed the release of acetylcholine and amino acid neurotransmitters evoked by sensory stimulation of the contralateral sensorimotor cortex via the brachial plexus. Naloxone (5 mg/kg) prevented all of these inhibitory actions of morphine. Naloxone also caused a significant increase in spontaneous acetylcholine release.

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.

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 sensori-motor and visual cortices have been studied using a superfusion technique. Electrical stimulation of the brachial plexus contra-lateral to the superfusion cannula increased significantly the release of glutamate and glutamine from the sensori-motor cortex of anesthetized rats. No clear effect was observed with the other amino acids. Stimulation of the ipsi-lateral plexus had no effect on glutamate and glutamine release. In unanesthetized animals, stimulation of the contra-lateral brachial plexus raised the levels of all the amino acids in sensori-motor 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 acid release were reversible at the cessation of the stimuli.