Effects of chronic alcohol administration on synaptic membrane Na+-Ca2+ exchange activity.
We have recently reported that ethanol and other n-alkanols added to in vitro assays inhibit the activity of the Na+-Ca2+ exchange system in brain synaptic plasma membrane vesicles. The present studies were undertaken to determine whether in vivo chronic ethanol administration leads to alterations in this Na+-Ca2+ antiporter that might be indicative of an adaptive response to alcohol. The Na+-dependent Ca2+ transport activity in the plasma-membrane fractions obtained was measured at various Ca2+ concentrations. Results of these experiments revealed that a 3-week ethanol regimen brought about a significant increase in the Na+-dependent Ca2+ transport activity only in the membrane fraction enriched in synaptic junctional complexes. These membranes showed a near doubling in the maximal transport activity of the antiporter in alcohol-treated compared with the control animals. Changes in the kinetic parameters were reversible as the Na+-Ca2+ exchange activity in these membranes from animals maintained on alcohol for 3 weeks and then withdrawn for 1 week was indistinguishable from that of membranes from control animals. Thus it appears that ethanol-treated animals make a reversible adaptation in their neuronal cell membranes to compensate for the acute effects of ethanol on the Na+-Ca2+ antiporter.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D013570:Synaptic Membranes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D013574:Synaptosomes / Q000378:metabolism / Q000648:ultrastructure
D002352:Carrier Proteins; D008565:Membrane Proteins; D019831:Sodium-Calcium Exchanger; D000431:Ethanol; D012964:Sodium; D002118:Calcium