Sustained ethanol inhibition of native AMPA receptors on medial septum/diagonal band (MS/DB) neurons.
The direct impact of ethanol on native, non-NMDA glutamate receptors was examined in acutely isolated MS/DB neurons from rat. The impact of ethanol functional tolerance and physical dependence on non-NMDA receptor function was also determined. Non-NMDA receptors were defined pharmacologically as predominantly the AMPA subtype, because both AMPA- or kainate-activated currents were blocked by GYKI 52466, a selective AMPA receptor antagonist. The relative magnitude of potentiation of AMPA-activated currents by 10 or 100 microM cyclothiazide was consistent with recombinant AMPA flop-subtype receptors. Finally, the selective kainate receptor agonist, SYM 8021, induced little current in MS/DB neurons. AMPA receptor currents when activated by kainate were sensitive to ethanol, showing inhibition of approximately 5 - 50% when 10 - 300 mM ethanol and kainate were briefly co-applied (3 s). Ethanol (100 mM) also inhibited both the initial transient peak and sustained currents activated by AMPA. Inhibition was sustained during continuous ethanol superfusions of 5 min, suggesting a lack of acute tolerance to ethanol-induced AMPA receptor blockade. Rapid application of 3 - 3000 microM kainate activated concentration-dependent currents in MS/DB neurons from Control and Ethanol Dependent animals that were not significantly different. Also, direct ethanol inhibition (300 mM) of kainate-activated currents was not reduced by ethanol dependence, suggesting a lack of functional tolerance. These results suggest that native AMPA receptors on MS/DB neurons are inhibited by pharmacologically-relevant concentrations of ethanol. However, these receptors, unlike NMDA receptors, do not undergo adaptation with sustained ethanol exposure sufficient to induce physical dependence. British Journal of Pharmacology (2000) 129, 87 - 94
Frye
G D
GD
Department of Medical Pharmacology and Toxicology, College of Medicine, Texas A&M Health Science Center, College Station, Texas, TX 77843-1114, USA. gdfrye@tamu.edu
Fincher
A
A
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D001569:Benzodiazepines; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D020667:Diagonal Band of Broca / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D009473:Neuronal Plasticity / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D018092:Kainic Acid Receptors / Q000819:agonists / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects; D020665:Septum of Brain / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D014151:Anti-Anxiety Agents; D001569:Benzodiazepines; D002492:Central Nervous System Depressants; D000431:Ethanol; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007608:Kainic Acid; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C061950:GYKI 52466