Neuropeptidergic control circuits in the spinal cord for male sexual behaviour: Oxytocin–gastrin‐releasing peptide systems

The neuropeptidergic mechanisms controlling socio-sexual behaviours consist of complex neuronal circuitry systems in widely distributed areas of the brain and spinal cord. At the organismal level, it is now becoming clear that “hormonal regulations” play an important role, in addition to the activation of neuronal circuits. The gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord is an important component of the neural circuits that control penile reflexes in rats, circuits that are commonly referred to as the “spinal ejaculation generator (SEG).” Oxytocin, long known as a neurohypophyseal hormone, is now known to be involved in the regulation of socio-sexual behaviors in mammals, ranging from social bonding to empathy. However, the functional interaction between the SEG neurons and the hypothalamo-spinal oxytocin system remains unclear. Oxytocin is known to be synthesised mainly in hypothalamic neurons and released from the posterior pituitary into the circulation. Oxytocin is also released from the dendrites of the neurons into the hypothalamus where they have important roles in social behaviours via non-synaptic volume transmission. Because the most familiar functions of oxytocin are to regulate female reproductive functions including parturition, milk ejection, and maternal behaviour, oxytocin is often thought of as a “feminine” hormone. However, there is evidence that a group of parvocellular oxytocin neurons project to the lower spinal cord and control male sexual function in rats. In this report, we review the functional interaction between the SEG neurons and the hypothalamo-spinal oxytocin system and effects of these neuropeptides on male sexual behaviour. Furthermore, we discuss the finding of a recently identified, localised “volume transmission” role of oxytocin in the spinal cord. Findings from our studies suggest that the newly discovered “oxytocin-mediated spinal control of male sexual function” may be useful in the treatment of erectile and ejaculatory dysfunction.

This is the peer reviewed version of the following article: [Oti T, Sakamoto H. Neuropeptidergic control circuits in the spinal cord for male sexual behaviour: Oxytocin–gastrin-releasing peptide systems. J Neuroendocrinol. 2023; 35(9):e13324. doi:10.1111/jne.13324], which has been published in final form at [https://doi.org/10.1111/jne.13324]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

This fulltext file will be available in Jul. 2024.