THE EFFECTS OF HYPOTHERMIA ON AMINO-ACID NEUROTRANSMITTER RELEASE FROM THE CEREBRAL-CORTEX

The effects of systemic hypothermia (33.5-degrees-C) on the ischemia-evoked release of the neurotransmitter amino acids, glutamate, aspartate, gamma-aminobutyric acid (GABA) and glycine into rat cerebral cortical superfusates were evaluated in the rat four vessel occlusion model. Glutamate, aspartate and GABA, but not glycine, levels were enhanced during and following a 20 min period of ischemia. However, when compared with normothermic ischemic animals, no reductions in glutamate, aspartate or GABA levels in the superfusates were apparent either prior to, during or following forebrain ischemic episodes. Indeed, the superfusate levels of aspartate and GABA were transiently increased immediately following ischemia. Glycine levels were significantly depressed, both pre- and post-ischemia, in cortical superfusates from hypothermic animals in comparison with normothermic rats.