Lack of influence of the phase of estrus cycle or treatment with steroid contraceptive drugs on cholinergic parameters in mouse and rat brain

Abstract

Acetylcholine and choline levels were found not to fluctuate with the phase of the estrus cycle in the cerebral hemispheres, deincephalon and mesencephalon in the rat and mouse. Choline acetyltransferase activity was not altered in these brain areas in the mouse while in the rat there was a small but significant decrease in the cerebral hemispheres during proestrus (p less than 0.01), and in the mesencephalon during estrus (p less than 0.05), both with respect to diestrus. Chronic 30-day treatment with steroid contraceptive drug combinations (lynestrenol, 5 mg/kg+ mestranol, 0.3 mg/kg; lynestrenol, 2.5 mg/kg+ mestranol, 0.15 mg/kg; norethindrone, 4 mg/kg+ mestranol, 0.2 mg/kg; norethynodrel, 4 mg/kg+ mestranol, 0.06 mg/kg) did not alter cholinergic parameters in the brain areas of these two species except for minor changes in rare instances.

PIP: Acetylcholine and choline levels and choline acetyltransferase activity were studied in mice and rats to determine whether these substances fluctuated with the phase of the estrous cycle or with subchronic and chronic treatment with steroid contraceptives. Acetylcholine and choline were determined in rat and mouse brain by the method of Saelens et al. Choline acetyltransferase activity was determined by a radiochemical method. The state of estrus was histologically determined daily. Steroid combi used included: 1) lynestrenol, 5mg/kg, plus mestranol, .3 mg/kg; 2) lynestrenol mg/kg, plus mestranol, .15 mg/kg; 3) norethindrone, 4 mg/kg, plus mestranol, .2 and 4) norethynodrel, 4 mg/kg, plus mestranol, .06 mg/kg. The levels of acetylcholine and choline were unaffected by the phases of the estrous cycle. During proestrus there was a small but significant (p less than .01) decrease in choline acetyltransferase activity in the cerebral hemispheres and a decrease in the mesencephalon during estrus (p less than .05). Chronic 30-day treatment with the steroid combinations were without effect on cholinergic parameters.