Temperature dependence of acetylcholine esterase activity in synaptic membranes from rat brain during hypothermia

Abstract

The degree of substrate inhibition of acetylcholine esterase activity decreases in plasma synaptosome membranes isolated from the cerebral cortex of rats subjected to short-term and prolonged hypothermia at 20~ while activation energy and breakpoint of the temperature curve in the Arrhenius coordinates remain unaffected. The observed changes are supposed to compensate the inhibitory effect of hypothermia on enzyme activity. Key Words: acetylcholine esterase; temperature dependence," synaptic membranes," hypothermia, ratsEven a short-term drop of core temperature to 20~ in homeothermic animals induces adaptive changes in the enzymatic apparatus in the brain [3]. A peak appears on the temperature plot of activity of the glutaminase isolated from synaptosome brain fraction, which corresponds to body temperature and suggests activation of temperature compensation of synaptic transmission, because glutaminase catalyzes synthesis of excitatory transmitter glutamate in glutamatergic synapses. The same changes probably take place in other neurotransmitter cerebral systems during hypothermia. Acetylcholine esterase (ACE) is a key enzyme in cholinergic cerebral synapses. Here we studied the temperature dependence of activity of this enzyme in rats subjected to 20~ hypothermia. MATERIALS AND METHODSThe study was carried out on 54 random-bred male albino rats weighing 170-200 g. The animals were divided into three groups. Group 1 rats were control, group 2 rats were subjected to 20~ hypothermia, and group 3 rats were subjected to a long-term hypothermia