Autoradiographic identification of estradiol-concentrating cells in the spinal cord of the female rat.

The topography and number of estradiol (E)-concentrating cells in the lower lumbar and sacral segments of the spinal cord of the female rat have been examined by the steroid autoradiography method. A nuclear-saturating does of E was administered by intravenous infusion, which kept blood estrogen at or above proestrus levels for 3.5-4 h, much longer than usual for steroid receptor studies. The cord segments selected for examination are known to receive somatosensory information relevant for estrogen-dependent behavior, and to contain some of the motoneurons for epaxial muscles responsible for this behavior. Small numbers of E-concentrating cells were found in the dorsal portion of the gray matter of L4, L5, L6 and the sacral segments. These cells were found in lamina II, in the midline region which includes lamina X, and the medial portions of laminae III, IV and V when they cross in the midline. E-concentrating cells were also found in the lateral portions of laminae III, IV, and V, and in lamina VII. Virtually no E-concentrating cells were found in the ventral portion of the gray matter or in the white matter. The spinal cord had few E-concentrating cells compared to the hypothalamus.