Androgenic regulation of gap junctions between motoneurons in the rat spinal cord

Gap junctional plaques were found between androgen-sensitive motoneurons of the spinal nucleus of the bulbocavernosus (SNB), using thin-section and freeze-fracture techniques. The somata and proximal dendrites of SNB motoneurons were studied after retrograde labeling with cholera toxin conjugated to HRP. Of the gap junctions observed, 45% were somatodendritic, 35% were dendrodendritic, and 20% were somatosomatic. The removal of testosterone by castration dramatically reduced the number and diameter of the junctional plaques, and these changes were prevented by testosterone treatment. The results are the first demonstration of hormonal regulation of morphologically identified gap junctions in the CNS. The occurrence and hormonal dependence of gap junctional plaques between motoneurons of the lumbar spinal cord indicate that androgens regulate the degree of coupling between these cells, which may allow for the synchronization and amplification of the electrical activity in the nucleus.