Asymmetric ovarian function is characteristic of humans, other higher primates, and Anolis lizards. That is, ovulation of a single egg occurs alternately from the right and left ovaries. The long-term objective of the present project is to understand the role of neural communication between the ovaries and the hypothalamus in controlling asymmetric ovarian function, using Anolis carolinensis as a model system. Knowledge gained may lead to an understanding in humans, and thereby have relevance in studies of menstrual cycles and fertility control. In Anolis females with growing ovaries in the spring, metabolism of monoamine neurotransmitters (norepinephrine, dopamine, and serotonin) is higher on the side of the smaller ovary (regardless of it being on the right or left side). Using a modified, reverse-phase, high performance liquid chromatography system and electrochemical (coulometric) detection, diencephalic monoamine metabolism will now be measured on the side of the larger and smaller ovary during the ovulatory cycles within the breeding season to determine if the brain alternates with the ovaries. The precise location of the monoamine asymmetries in the hypothalamus will be explored by the use of immunohistochemistry to detect the presence of the monoamines as well as their synthetic enzymes (tyrosine hydroxylase and dopamine-beta- hydroxylase). Quantification of immunohistochemically reactive neuronal cell bodies and fibers will employ a computer image analysis system. Possible hypothalamic asymmetry in luteinizing hormone-releasing hormone (LHRH) in relation to ovarian asymmetry will be investigated using LHRH radioimmunoassay and immunohistochemistry. To test the hypothesis that the dominant (larger) ovary controls the hypothalamic asymmetries, females will be subjected to surgical removal of the entire larger ovary, largest follicle in the larger ovary, or corpus luteum in the smaller ovary, and the consequent effects on hypothalamic asymmetry of monoamines and LHRH as well as on ovarian alternation will be explored. The influence of the uterus on the hypothalamic asymmetries will also be investigated using unilateral hysterectomy.
