Doctor of Philosophy
Anatomy and Cell Biology
Dr. Lique M. Coolen
Ejaculatory dysfunction impacts large numbers of men of all ages and around the world. In addition, a great majority of men with chronic spinal cord injury (SCI) experience ejaculatory dysfunction, which negatively impacts the quality of life of these individuals and their partners. SCI men emphasize the significance of regaining sexual function as their main goal. Currently, there is a marked absence of literature reporting the alterations to sexual function and ejaculation in particular in animal models of chronic SCI. In addition, there are many unanswered questions pertaining to the spinal cord control of ejaculation in healthy, intact men. It is known that ejaculation is controlled by a population of lumbar spinothalamic (LSt) cells in the lumbar spinal cord through their direct projections to preganglionic autonomic and motor neurons in the lumbosacral spinal cord. It is hypothesized that LSt cells control ejaculatory reflexes through the release of their neuropeptides galanin, cholecystokinin (CCK), gastrin-releasing peptide (GRP), and enkephalin onto receptors in autonomic and motor areas of the lumbosacral spinal cord. This hypothesis was tested in this thesis utilizing a paradigm in anesthetized and spinalized male rats, with stimulation of the sensory inputs via the dorsal penile nerve. Consistent with the hypothesis, mu and delta opioid receptor, galanin, CCK, and GRP receptor activation in LSt target areas in the lumbosacral spinal cord was demonstrated to be critical for ejaculatory reflexes. Next, the hypothesis that intrathecal infusions of the LSt neuropeptides can improve ejaculatory reflexes in male rats with chronic SCI was tested. Results indicated that intrathecal infusions of GRP and the mu opioid receptor agonist DAMGO improved ejaculatory reflexes in male rats with chronic contusion SCI. Finally, the hypothesis that the D3 receptor agonist 7-OH-DPAT will recover ejaculatory function in male rats with chronic spinal cord injury was tested. Indeed, systemic infusions of 7-OH-DPAT greatly improved ejaculatory reflexes in SCI males. Together, the studies in this thesis further clarified the mechanisms involved in the spinal cord control of ejaculation in male rats and represent an initial but pivotal first step towards the recovery of ejaculatory function after chronic spinal cord injury.
Kozyrev, Natalie, "Spinal Cord Control of Ejaculatory Reflexes in Male Rats" (2013). Electronic Thesis and Dissertation Repository. 1596.