Hyperthermia influences excitatory and inhibitory amino acid neurotransmitters in the central nervous system. An experimental study in the rat using behavioural, biochemical, pharmacological, and morphological approaches.
Role of excitatory amino acids, glutamate, aspartate, and inhibitory amino acids, gamma aminobutyric acid (GABA) and glycine in brain damage caused by heat stress was examined in a rat model. Subjection of rats to 4 h heat stress at 38 degrees C in a biological oxygen demand (BOD) incubator resulted in a marked increase in glutamate and aspartate in some brain regions, whereas a significant decline in GABA and glycine was observed in several brain areas. Profound behavioural alterations and impairment of motor and cognitive functions were seen at this time. Breakdown of the blood-brain barrier (BBB), reduction in regional cerebral blood flow (CBF), edema formation and cell injuries are prominent in several parts of the brain. Pretreatment with multiple opioid receptor antagonist, naloxone (10 mg/kg, i.p.) significantly restored the heat stress induced decline in GABA and glycine and thwarted the elevation of glutamate and aspartate in various brain areas. The motor or cognitive deficits were also attenuated. A significant reduction in BBB permeability, cerebral blood flow abnormalities, edema formation and cell injuries was evident. These novel observations suggest that (i) glutamate, aspartate, GABA and glycine are involved in the pathophysiology of heat stress, and (ii) a balance between excitatory and inhibitory amino acids in brain is crucial in hyperthermia induced brain injuries or repair.
Laboratory of Cerebrovascular Research, Department of Surgical Sciences, Anaesthesiology and Intensive Care Medicine, University Hospital, Uppsala University, Uppsala, Sweden. Sharma@surgcsi.uu.se
H S
HS
Sharma
D000818:Animals; D001224:Aspartic Acid / Q000187:drug effects / Q000378:metabolism; D001522:Behavior, Animal / Q000502:physiology; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D003071:Cognition / Q000187:drug effects / Q000502:physiology; D004487:Edema / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D018846:Excitatory Amino Acids / Q000378:metabolism*; D018698:Glutamic Acid / Q000187:drug effects / Q000378:metabolism; D005998:Glycine / Q000187:drug effects / Q000378:metabolism; D006979:Hyperthermia, Induced; D007091:Image Processing, Computer-Assisted; D008297:Male; D046529:Microscopy, Electron, Transmission; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D005680:gamma-Aminobutyric Acid / Q000187:drug effects / Q000378:metabolism
D018846:Excitatory Amino Acids; D009292:Narcotic Antagonists; D018377:Neurotransmitter Agents; D001224:Aspartic Acid; D009270:Naloxone; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005998:Glycine