Chronic Ethanol Consumption Affects Filipin‐Cholesterol Complexes and Intramembranous Particles of Synaptosomes of Rat Brain Cortex

Abstract

To assess the effect of ethanol on the planar distribution of cholesterol as well as on the surface architecture of presynaptic terminals of rats, synaptosomes isolated from cerebral cortex of rats chronically exposed to alcohol were incubated with filipin, a cytochemical marker for beta-hydroxycholesterol, and analyzed using both conventional (qualitative and quantitative) and freeze-fracture electron microscopy. Synaptosomes incubated in the absence of filipin were used as cytochemical controls. Biochemical determination indicates a 12% increase of cholesterol in synaptosomal membranes from alcohol treated rats. This increase was confirmed by a significant increment in the number of filipin-cholesterol complexes. Synaptosomes of treated rats showed a reduction in the total number of synaptic vesicles (SV) as well as a decrease in the density and total number of intramembranous particles (IMP) per synaptosome. In control rats, most synaptosomal IMP were distributed in clusters whereas in those of rats exposed to alcohol they were distributed at random. These changes in distribution of IMP were also observed in presynaptic terminals analyzed "in situ." These findings indicate that ethanol acts on the presynaptic terminals. The variations in cholesterol content as well as in the density and distribution of IMP appear to be related to alcohol-induced changes in the physicochemical properties of components of the synaptosomal membrane.

Ethanol‐Induced Oxygen Radical Formation and Lipid Peroxidation in Rat Brain: Effect of Chronic Alcohol Consumption

“…Using the same procedure of alcohol administration, we have previously demonstrated that chronic alcohol intake induces metabolic tolerance (Sancho-Tello et al ., 1988) and changes in the physicochemical properties of rat synaptic membranes (Guerri and Grisolfa, 1983 ;Renau-Piqueras et al ., 1987) .…”

Effects of Chronic Ethanol Consumption on Brain Synaptosomes and Protective Role of Betaine

“…In addition to this, ethanol has several effects on synaptic structures of brain such as altering lipid structure and composition of synaptic membranes [9,10], decreasing the number of synaptic vesicles (SV) while increasing intramembranous particles [11] and inhibiting plasma membrane and mitochondrial transmembrane potentials [12]. Acetaldehyde also decreases the viscosity of hydrophobic regions of bulk membrane lipids [13].…”

Ultrastructural alterations of choroid plexuses of lateral ventricles of rats (Rattus norvegicus) submitted to experimental chronic alcoholism

“…Thus enzymatic changes as well as changes in the membranes, induced by ethanol or its direct action, may lead to problem in circulation of fluids among membranes, being the responsible for cerebrospinal fluid accumulation in intercell space and between capillaries and choroid epithelium thus contributing to the impairment in the production of cerebrospinal fluid by choroid plexuses 3,18,19 . Vesicles containing electronlucent material were observed all over the cytoplasm due to a greater penetration of fluid in cytoplasm of choroid cells resulting from fluid accumulation in intercellular space and connective tissue.…”

“…It is supposed that 2 to 6 hours after its ingestion, the alcoholic concentration in the CNS is close to that found in the blood, being the responsible factors the neurotropism of alcohol and the great blood irrigation of CNS 2 . So in adult rats ethanol changes physical properties of cerebral biomembranes (Goldstein, 1984 and Taraschi & Rubin, 1985 cited by Renau-Piqueras et al) 3 affecting the cerebral vascular permeability 12 easily crossing the hemato-encephalic barrier, spreading itself by diffusion to the interior of adjacent tissues 13 and resulting in histopathological and chemical alterations of the brain [14][15] . As it was suggested by Jarnefelt 16 alcohol prevents the active transport mechanism of sodium through choroid plexuses, which explains the several effects of alcohol in intact nervous cells.…”

“…Goldstein (1984) and Traschi & Rubin (1985) observed in adult rats that ethanol modifies physical properties of cerebral biomembranes (cited by Renau-Piqueras et al) 3 . Ultrastructural changes were observed by Checiu et al 4 in fetal neo-cortex of rats due to chronic maternal alcoholization.…”