Unilateral Ovariectomy Influences Hypothalamic Monoamine Asymmetries in a Lizard (Anolis) That Exhibits Alternation of Ovulation

Abstract

The lizardAnolis carolinensisalternates ovulation, and the resultant ovarian asymmetry correlates with alternating asymmetry of hypothalamic catecholamines. Unilateral and bilateral ovariectomies of cycling females were performed to determine if ovarian manipulations influence hypothalamic catecholamine asymmetries. During the middle of the ovarian cycle, we removed the larger ovary, i.e., the next one to ovulate an egg (N=9), the smaller ovary with its corpus luteum (N=8), or both ovaries (N=5). A sham-operated control group was included (N=9). The diameter of the largest ovarian follicle in each ovary was measured at the beginning and end of the experiment. After 12 days, the hemihypothalami from the sides of the initial smaller ovary (SO) and larger ovary (LO) were dissected and frozen for determination of monoamines and their metabolites using HPLC and electrochemical detection. Monoamine and metabolite concentrations at the end of the experiment in the 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. Removal of the SO or LO caused the AR of DOPAC to favor the brain side ipsilateral 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 the 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 symmetric, and removal of the LO caused the 5-HIAA AR to favor the LO side. We conclude that the ovaries influence hypothalamic catecholamine asymmetries inAnolisvia direct neural (as well as hormonal) pathways and that sensory input from the ovaries to the hypothalamus could be involved in control of ovarian alternation via both neural and hormonal efferent mechanisms.