Time changes in Na+,K(+)-ATPase, Mg(++)-ATPase, and acetylcholinesterase activities in the rat cerebrum and cerebellum caused by stress.

Na+,K(+)-ATPase, Mg(++)-ATPase, and acetylcholinesterase activities were determined in homogenated rat cerebrum and cerebellum in unstressed animals (control) and exposed to cold and immobilization for 45-180 min. Na+,K(+)-ATPase and Mg(++)-ATPase activities were not affected within the first 80 min of stress, while they were increased about 50-70% after 120-180 min, where the maximum enzyme stimulation was observed. However, acetylcholinesterase activity was increased considerably by less than 45 min of stress and reached a plateau in 80-180 min to a higher value in the cerebrum (approximately equal to 100%) than in the cerebellum (approximately equal to 40%) related to the control. Our results suggest that: a) The stress used can stimulate acetylcholinesterase in a different way and more quickly than Na+,K(+)-ATPase and Mg(++)-ATPase; b) acetylcholinesterase in the cerebellum is stimulated to a lower level than in the cerebrum by stress, probably because of the presence of a relatively small cerebellar cholinergic innervation.