Effect of sex steroids on choline acetyltransferase and acetylcholinesterase of cerebral hemisphere of male rats of various ages

Abstract

The specific activities of choline acetyltransferase and acetylcholinesterase of the cerebral hemisphere of 8-, 40- and 80- week old male rats were estimated, and were found to decrease as a function of age. Castration decreases the activities of both the enzymes in young and adult rats. However, in the old, the activity of choline acetyltransferase alone is affected by castration. Testosterone (10 μg/100 g body weight) administered to castrated rats increases the activity of choline acetyltransferase at all ages, whereas 100 μg of testosterone stimulates choline acetyltransferase only in the young castrated rats. Estradiol (10 μg) stimulates choline acetyltransferase in young and adult rats, but not in old rats, whereas 100 μg estradiol is effective in stimulating choline acetyltransferase only in young rats. A low dose of testosterone (10 μg) decreases the activity of acetylcholinesterase in young castrated rats, but increases it in both adult and old rats. A higher dose of testosterone (100 μg) stimulates acetylcholinesterase only in adult rats. Estradiol (10 μg) increases the activity of acetylcholinesterase at all the ages, but a higher dose (100 μg) increases it in castrated young rats only. The data suggest a decline of cholinergic function in the brain of rats after the attainment of maturity. Furthermore, the activities of both choline acetyltransferase and acetylcholinesterase can be altered by sex steroids; however, this is dependent on the age of the animal.