Mediation of Some Effects of Illumination on the Rat Estrous Cycle by the Sympathetic Nervous System

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Abstract
When mature rats are placed in continuous illumination, their “incidence of estrus” (percentage of daily vaginal smears showing proestrus, estrus or metestrus) is enhanced; darkness has the opposite effect. Removal of the eyes or of both superior cervical ganglia blocks this effect of light. These procedures also eliminate the light-induced hypertrophy of the ovaries and the uterus and prevent the associated decreases in pineal weight and melatonin-synthesizing ability. These findings demonstrate that the autonomic nervous system plays a role in the regulation of the rat estrous cycle, and suggest that this role may involve control of melatonin synthesis in the pineal gland. (Endocrinology75: 266, 1964)