Temperature dependencies of acetylcholinesterase activity in synaptosomal membranes from brain cortex of suslics at artificial hypothermia and hibernation

Temperature dependence of kinetic characteristics of acetylcholinesterase ( AChE) in synaptosomal membranes of ground squirrel's Citellus pigmaeus brai n was investigated in awake, hibernating, and hypothermic (rectal temperatu re 10 degreesC) states. Hibernation and hypothermia lead to an increase of V-m and enhance the degree of substrate inhibition of AChE. The value of K- app remains unchanged. There are two linear segments in Arrhenius plots for temperature dependence of AChE activity with breakpoints at 26.3, 21.0, an d 18.7 degreesC for awake, hypothermic, and hibernating animals, respective ly. The mechanisms and biological role of changes in AChE kinetic character istics at hibernation are discussed.