Changes in the striatal extracellular levels of dopamine and dihydroxyphenylacetic acid evoked by ammonia and N-methyl-D-aspartate: modulation by taurine.
Acute hyperammonemia is associated with motor disturbances that are thought to involve striatal dopaminergic dysfunction. Discharge of striatal dopaminergic neurons is controlled by N-methyl-D-aspartate (NMDA) receptors, the excessive activation of which contributes to ammonia neurotoxicity. Here we show that ammonium chloride ("ammonia", extracellular concentration 5 mM) or NMDA (1 mM), when directly administered to the rat striatum via a microdialysis probe, evoke a prompt accumulation of dopamine (DA) in the microdialysates. However, while ammonia increases, NMDA decreases, the extracellular dihydroxyphenylacetate (DOPAC) level. The results point to the NMDA receptor-mediated enhancement of DA release and increased DA metabolism as two independent ways by which ammonia affects the striatal dopaminergic system. Taurine (extracellular concentration 10 mM) attenuated the NMDA- and ammonia-evoked DA release and ammonia-induced accumulation of DOPAC, reflecting two different neuroprotective mechanisms of this amino acid.
Anderzhanova
Elmira
E
Brain Research Center, University of Tampere Medical School, Tampere, Finland.
Oja
Simo S
SS
Saransaari
Pirjo
P
Albrecht
Jan
J
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism*; D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D004347:Drug Interactions; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005110:Extracellular Space; D008297:Male; D017551:Microdialysis; D016202:N-Methylaspartate / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013654:Taurine / Q000494:pharmacology*; D013997:Time Factors
D018690:Excitatory Amino Acid Agonists; D015102:3,4-Dihydroxyphenylacetic Acid; D013654:Taurine; D016202:N-Methylaspartate; D000641:Ammonia; D004298:Dopamine