Effect of hypoxia on cholinesterase activity in rat sensorimotor cortex

Abstract

This study reports the dynamics of changes in postnatal ontogenesis of the activity of soluble and membrane-bound forms of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in sensorimotor cortex of rats as well as the pattern of their changes after prenatal hypoxia (E14, 7% O2, 3 h) or acute hypoxia in adult animals (4 months, 7% O2, 3 h). In normally developing rats the activity of the membrane-bound AChE form in the sensorimotor cortex gradually increased up to the end of the first month after birth and remained at this high level during all further postnatal ontogenesis, while the activity of the soluble form of AChE reached its maximum on the 10th day after birth and decreased significantly by the end of the first month. In animals exposed to prenatal hypoxia the activity both of the soluble and membrane bound forms of AChE during the first two weeks after birth was 20-25% lower, as compared to controls but increased by the end of the first month and even exceeded the control values remaining increased up to old age (1.5 years). The activity of both BChE forms in rat sensorimotor cortex at all stages of postnatal ontogenesis was significantly lower than of AChE, although the dynamics of their changes was similar to that of AChE. Prenatal hypoxia led to a decrease in the activity of the membrane-bound form of BChE, as compared to controls, practically at all developmental stages studied, but was higher at the end of the first month after birth. At the same time, the activity of the soluble form of BChE was decreased only on the 20th day of development, as compared to the control, but increased from the end of the first month of life onwards. Acute hypoxia in adult rats also led to a decrease in the activity of both forms of AChE and BChE in the sensorimotor cortex but the dynamics of these changes was different for each enzyme. Thus, insufficient oxygen supply to the nervous tissue at different stages of ontogenesis has a significant effect on the activity and ratio of various forms of cholinesterases exhibiting either growth factor or signaling properties. This may lead to changes in brain development and formation of behavioural reactions, including learning and memory, and also increase the risk of development of the sporadic form of Alzheimer's disease (AD)--one of the most common neurodegenerative diseases of advanced age. This study expands our knowledge of the properties of brain cholinesterases under normal and pathological conditions and may be useful for developing new approaches towards prevention and treatment of AD.