Effects of Ethanol on the Activity of Brain Enzymes

Abstract

Ethanol alters, in a selective manner, the activity of several membrane-bound enzymes in the central nervous system (CNS) which are important for neuronal transmission of information. Ethanol inhibits Na^+/K^+-transporting ATPase activity, while adenylate cyclase (AC) activity is stimulated by ethanol added in vitro. Ethanol’s effects on AC activity are mediated primarily via effects on proteins that regulate AC activity. Ethanol has selective effects on monoamine oxidase activity, in that the B form of the enzyme is more sensitive to inhibition by ethanol added in vitro. The selective effects of ethanol on different membranebound CNS enzymes may result from differing membrane lipid microenvironments of the enzymes, or from differences in the enzyme proteins per se.

Phospholipase C activation by ethanol in rat hepatocytes is unaffected by chronic ethanol feeding

“…It should be pointed out that it is not unusual for ethanolsensitive processes to maintain their responsiveness to ethanol added in vitro, even after an adaptive response has been initiated in the animal by ethanol feeding. Many ethanol-sensitive enzymes show an alteration in their baseline activity in ethanol-fed animals which compensates for the effects of ethanol, so that the activity in the ethanol-fed animal exposed to acute ethanol would be comparable with the control activity in the absence of ethanol [2,4]. This pattern has been observed, for instance, in the adaptive response of the adenylate cyclase-coupled G-protein Gs, which is decreased after long-term ethanol treatment in vitro and in vivo [23].…”

“…Long-term ethanol intake in rats and other animals causes adaptive changes in different tissues at the cellular and subcellular levels, allowing the system to function normally in the presence of significant circulating concentrations of ethanol (which may be in the order of 25-50 mM) [1]. These adaptive responses generally involve processes which are affected by ethanol in vitro, ranging from specific enzyme activities (e.g., Na+/K+-ATPase, monoamine oxidase [2]), to complex integrated functions, such as oxidative phosphorylation and transmembrane signal transduction [1,3,4]. Many of the processes affected by ethanol are membrane-associated; hence the ability of ethanol to interact with biological membranes has been proposed to be an essential element in these adaptive responses [1,3].…”

Influences of ethanol ingestion on olfactory function in humans

“…Hence, this measure may be subtly influenced by higher-order processes that are not immediately apparent, including alterations in attention, possibly via the reticular formation (Person and Gunn 1974;Hetzler et al 1987). Alcohol is known to have general pharmacological effects on the central nervous system (e.g., on GABAergic, dopaminergic, and opioidergic systems), as well as direct effects on nerve cell membranes, so the potential loci for its effects are multiple (Tytell and Myers 1973;Tabakoff et al 1978Tabakoff et al , 1987Arendt et al 1988).…”