Localization and controls of aromatase in the quail spinal cord

In adult male and female Japanese quail, aromatase-immunoreactive cells wer e identified in the spinal dorsal horns from the upper cervical segments to the lower caudal area. These immunoreactive cells are located mostly in la minae I-III, with additional sparse cells being present in the medial part of lamina V and, at the cervical level exclusively, in lamina X around the central canal. Radioenzyme assays based on the measurement of tritiated wat er release confirmed the presence of substantial levels of aromatase activi ty throughout the rostrocaudal extent of the spinal cord. Contrary to what is observed in the brain, this enzyme activity and the number of aromatase- immunoreactive cells in five representative segments of the spinal cord are not different in sexually mature males or females and are not influenced i n males by castration with or without testosterone treatment. The aromatase activity and the numbers of aromatase-immunoreactive cells per section are higher at the brachial and thoracic levels than in the cervical and lumbar segments. These experiments demonstrate for the first time the presence of local estrogen production in the spinal cord of a higher vertebrate. This production was localized in the sensory fields of the dorsal horn, where es trogen receptors have been identified previously in several avian and mamma lian species, suggesting an implication of aromatase in the modulation of s ensory (particularly nociceptive) processes. J. Comp. Neurol. 423:552-564, 2000. (C) 2000 Wiley-Liss, Inc.