Age-related changes in acetylcholinesterase and its molecular forms in various brain areas of rats

Abstract

A previous study conducted in this laboratory revealed a decrease in total cholinesterase (total ChE) in the cerebral cortex, hippocampus and striatum in aged rats (24 months) of various strains, as compared with young animals (3 months). The purpose of the present experiments was to extend the study to other brain areas (hypothalamus, medulla-pons and cerebellum) and to assess whether this decrease was dependent on the reduction of either specific acetylcholinesterase (AChE) or butyrylcholinesterase (BuChE) or both. By using ultracentrifugation on a sucrose gradient, the molecular forms of AChE were evaluated in all the brain areas of young and aged Sprague-Dawley rats. In young rats the regional distribution of total ChE and AChE varied considerably with respect to BuChE. The age-related loss of total ChE was seen in all areas. Although there was a reduction of AChE and, to somewhat lesser extent, of BuChE in the cerebral cortex, hippocampus, striatum, and hypothalamus (but not in the medulla-pons or the cerebellum), the ratio AChE/BuChE was not substantially modified by age. Two molecular forms of AChE, namely G4 (globular tetrameric) and G1 (monomeric), were detected in all the brain areas. Their distribution, expressed as G4/G1 ratio, varied in young rats from about 7.5 for the striatum to about 2.0 for the medulla-pons and cerebellum. The age-related changes consisted in a significant and selective loss of the enzymatic activity of G4 forms in the cerebral cortex, hippocampus, striatum, and hypothalamus, which resulted in a significant decrease of the G4/G1 ratio. No such changes were found in the medulla-pons or the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Nature of stress: Differential effects on brain acetylcholinesterase activity and memory in rats

“…The AChE enzyme exists in different molecular isoforms that are localized differentially in neuronal cell (Meneguz et al, 1992). The two major isoforms are globular monomer (G1) protein and globular tetramer (G4) of the same monomer subunit.…”

In vitro inhibitory effect of aflatoxin B1 on acetylcholinesterase activity in mouse brain

“…The molecular isoforms of AChE were separated by ultracentrifugation in sucrose gradient as previously described (Bisso et al, 1991;Meneguz et al, 1992). In brief, the homogenates were centrifuged at 100,000 × g for 1 h in a Centrikon T-1055 (Kontron) ultracentrifuge and 200 l of supernatant was layered on 4.8 ml of 5-20% linear sucrose gradient and centrifuged at 38,000 rpm in a SW55B rotor for 18 h. In some experiments, catalase (11.3 S) and bovine serum albumin (4.3 S) were used as sedimentation standards.…”

“…Aliquots (100 l) of the supernatants (diluted 1:10 in distilled water) were used as the enzyme source. AChE activity was determined by Ellman's spectrophotometric method (Ellman et al, 1961) as already described (Volpe et al, 1990;Meneguz et al, 1992). AcThCh 0.56 mM was used as substrate and brain homogenates were incubated in 0.05 M sodium phosphate buffer, pH 7.2, for 30 min at 25 • C.…”

Acetylcholinesterase Activity of Synaptic Plasma Membranes during Ageing: Effect of <i>L</i>-Acetylcarnitine

“…Most of the studies done to evaluate the age-dependent changes of cerebral membrane constituents have been performed on whole brain homogenate or myelin fraction [28]. In addi tion, intervals of only 10-12 months in the life-span of experimental animals were considered [25,[27][28][29][30], On the contrary, the present study was undertaken to explore systematically the development-and age-depen dent changes of AChE activity at 4, 8, 12, 16, 20 and 24 m onths of age, at the level of the specific cerebral subcellular structure, where the enzyme is located in vivo, i.e. the synaptic plasma membranes of a selected functional region of rat brain, the frontal cerebral cortex.…”