UNILATERAL OVARIECTOMY INFLUENCES HYPOTHALAMIC MONOAMINE ASYMMETRIES IN A LIZARD (ANOLIS) THAT EXHIBITS ALTERNATION OF OVULATION

The lizard Anolis cavolinensis alternates ovulation, and the resultant ovarian asymmetry correlates with alternating asymmetry of hypothalam ic catecholamines. Unilateral and bilateral ovariectomies of cycling f emales were performed to determine if ovarian manipulations influence hypothalamic catecholamine asymmetries. During the middle of the ovari an cycle, we removed the larger ovary, i.e., the next one to ovulate a n egg (N = 9), the smaller ovary with its corpus luteum (N = 8), or bo th ovaries (N = 5). A sham-operated control group was included (N = 9) . The diameter of the largest ovarian follicle in each ovary was measu red at the beginning and end of the experiment. After 12 days, the hem ihypothalami from the sides of the initial smaller ovary (SO) and larg er ovary (LO) were dissected and frozen for determination of monoamine s and their metabolites using HPLC and electrochemical detection. Mono amine and metabolite concentrations at the end of the experiment in th e original SO and LO sides of each hypothalamus were compared with an asymmetry ratio, or AR, of (SO side - LO side)/(SO side + LO side). No female ovulated during the experiment. Unilateral ovariectomy caused compensatory growth of the largest follicle in the remaining ovary. Re moval of the SO or LO caused the AR of DOPAC to favor the brain side i psilateral to that of the ovarian removal. Removal of the LO switched the NE AR from the SO to the LO side. Removal of the LO or SO caused t he MHPG AR to favor the LO side. Ovariectomy of any kind caused 5-HT, which in the sham-operated animals favored the SO side, to become symm etric, and removal of the LO caused the 5-HIAA AR to favor the LO side . We conclude that the ovaries influence hypothalamic catecholamine as ymmetries in Anolis via direct neural (as well as hormonal) pathways a nd that sensory input from the ovaries to the hypothalamus could be in volved in control of ovarian alternation via both neural and hormonal efferent mechanisms. (C) 1997 Academic Press.