Abstract
The distribution of the estrogen synthesizing enzyme (aromatase) in the hindbrain (rhombencephalon and mesencephalon) of male adult quail was investigated by immunocytochemistry. Aromatase-immunoreactive neuronal structures (perikarya and fibers bearing punctate structures) were observed in sensory (trigeminal, solitary tract, part of the vestibular, optic tectum) and integrating (parabrachial, periaqueductal, cerulean, raphe) nuclei. Besides the expression of aromatase in these well delineated nuclei, dense to scattered networks of immunoreactive fibers were found quasi-ubiquitously in the hindbrain and, in particular, in its rostral and dorsal parts. To a lesser extent, they were also present throughout the premotor nuclei of the reticular formation and in various fiber tracts. In contrast, no immunoreactive signal was found in motor regions and in most of the statoaccoustic (cerebellum, vestibular, cochlear, olive, pontine) nuclei. The expression of aromatase in perikarya and fibers in areas of the adult hindbrain where estrogen receptors have been previously identified suggests a role for locally produced estrogens in the control of sensory and coordinating functions contrary to the widespread assumption that these functions are controlled by steroids produced by the gonads. We had previously demonstrated the presence of aromatase in neurons of the dorsal (sensory) horn of the spinal cord in quail. The present work shows that aromatase-immunoreactive structures are in fact broadly distributed in sensory nuclei in the caudal part of the quail brain and allows to extend the concept of spinal sensory aromatase to the broader concept of sensory aromatase according to which estrogens produced in sensory nuclei of the hindbrain could control a diversity of sensory processes.
