Localization of estrogen-synthase (aromatase) in the rat spinal cord

The cytochrome P-450 aromatase catalyses the transformation of aromatizable androgens into estrogens. Androgen aromatization occurs locally in specific brain areas and is critical for the activation of male sexual behavior. Estrogens also regulate somatosensory processes, especially nociception presumably by activating estrogen receptors distributed throughout the rostrocaudal extent of the spinal dorsal horns. In the dorsal horns, neurons receive sensory information from peripheral afferent fibers, process it and/or relay it to other (supra)spinal sites. We recently demonstrated that in Japanese quail aromatase is present in neurons (soma and fibers) all along the dorsal horns. We assessed here the presence of aromatase-immunoreactive (ARO-ir) structures in the spinal cord of adult rats with polyclonal antibodies raised against human or quail recombinant aromatase. Despite the fact that earlier studies failed to detect aromatase activity in the rat spinal cord, both antibodies revealed numerous intensely stained ARO-ir fibers and varicosities running rostrocaudally in laminae I-II, X, and in the Lissauer tract. Stained perikarya could not be observed. The ARO-ir fibers and varicosities were not detected by antibodies pre-adsorbed with their respective antigen. With the exception of the lack of soma staining, the distribution of ARO-ir material is similar to that described in quail. Although the origin of these ARO-ir fibers remains to be determined, their presence reinforces the hypothesis of a local regulation of estrogen synthesis and action in the spinal cord that could modulate somatosensory processes on a local basis