INHIBITION OF SYNAPTOSOMAL CALCIUM-UPTAKE BY ETHANOL

  • 1 January 1980
    • journal article
    • research article
    • Vol. 213  (3) , 562-568
Abstract
In vitro addition of ethanol or pentobarbital to synaptosomes isolated from rat or mouse brain inhibited the depolarization-dependent uptake of Ca without affecting uptake under nondepolarizing conditions. Ethanol inhibited the uptake in a concentration-dependent manner over the range of 45-720 mM. Analysis of the effects of ethanol and pentobarbital on Ca uptake at different temperatures indicated that the drugs did not change the activation energy of the process but shifted the Arrhenius curves toward higher temperatures. Synaptosomes isolated from mice chronically ingesting ethanol were tolerant to the inhibitory effects of ethanol and pentobarbital but not tolerant to the inhibitory effects of acetaldehyde. Synaptosomes from ethanol tolerant-dependent mice accumulated less Ca in the absence of ethanol than did synaptosomes from control mice. This depression of uptake was reversed by in vitro exposure of the synaptosomes to a low concentration of ethanol; it may represent a biochemical response to withdrawal of alcohol. A single acute injection of ethanol 1 h before sacrifice did not alter the Ca uptake activity or the drug sensitivity of the synaptosomes. The inhibitory effects of ethanol and pentobarbital on the stimulated release of neurotransmitters and the development of tolerance to these effects may be mediated by the inhibition of the depolarization-dependent influx of Ca by the drugs.