Effect of alpha 2-adrenergic drugs dexmedetomidine and atipamezole on extracellular amino acid levels in vivo.
alpha 2-Adrenoceptors are known to be involved in a variety of physiological functions and pathological conditions, including epilepsy and the extent of excitotoxin-induced cell death. In this study we evaluated whether selective alpha 2-adrenergic drugs can modulate the release of neurotransmitter amino acids. The effect of the alpha 2-adrenoceptor agonist dexmedetomidine (5 micrograms/kg, s.c.) and the alpha 2-adrenoceptor antagonist atipamezole (0.1 mg/kg and 1 mg/kg, s.c.) on the release of extracellular glutamate, aspartate and gamma-aminobutyric acid (GABA) was studied with microdialysis in the hippocampus of freely moving rats under basal and K(+)-evoked conditions. Atipamezole (1 mg/kg) decreased K(+)-evoked glutamate efflux by 30% compared to the control group (P < 0.05) but did not affect significantly the effluxes of aspartate and GABA. Dexmedetomidine and the lower dose of atipamezole (0.1 mg/kg) did not significantly alter the evoked overflow of amino acids. The results suggest that alpha 2-adrenergic drugs have only modest effects on the K(+)-stimulated overflow of extracellular neurotransmitter amino acids in rat hippocampus.
Valtonen
P
P
A.I. Virtanen Institute, University of Kuopio, Finland.
Haapalinna
A
A
Riekkinen
P
P
Halonen
T
T
D058647:Adrenergic alpha-2 Receptor Agonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D004827:Epilepsy / Q000503:physiopathology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine; D017551:Microdialysis; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012640:Seizures / Q000517:prevention & control; D013050:Spectrometry, Fluorescence; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D058647:Adrenergic alpha-2 Receptor Agonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000596:Amino Acids; D007093:Imidazoles; C050701:atipamezole; D001224:Aspartic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D020926:Medetomidine; D011188:Potassium; D002118:Calcium