IMMUNOHISTOCHEMICAL CHARACTERIZATION OF A SPINAL CORD GENERATOR OF EJACULATION IN HUMAN

Clinical observations strongly suggest that a spinal neuronal organization commanding ejaculation exists in man that can be activated in spinal cord injured patients by penile vibratory stimulation despite disruption of cerebral connections. In the rat, a spinal generator of ejaculation (SGE) in 3rd and 4th lumbar (L3-L4) segments has been identified which is notably characterized by the presence of a variety of markers including receptors and neuropeptides onto the constituting neurons immunoreactive for galanin. An immunohistochemical study was conducted to identify in human lumbar spinal cord neuronal organization that shares similarities with the rat SGE. Post-mortem men and women (n=3 each) spinal cord specimens were processed for immunodetection of galanin neurons, which distribution was 3D reconstructed. Co-expression with galanin of the molecular markers of the rat SGE (androgen and neurokinin-1 receptors, cholecystokinin, gastrin-releasing peptide, met-enkephalin) was assessed using confocal microscopy. Galanin neurons were mostly located between L2 and L5 segments in medial lamina VII, with a maximum within L4. Three dimension reconstruction of spinal cord sections showed that galanin neurons were grouped into single columns bilaterally to the central canal. Galanin neurons were found in greater number in men than in women specimens indicating sexual dimorphism. In addition, a vast majority of L3-L4 galanin neurons were immunoreactive for cholecystokinin, gastrin-releasing peptide, met-enkephalin, androgen and neurokinin-1 receptors.