Oti Takumi, Sakamoto Hirotaka
Department of Biological Sciences, Faculty of Science, Kanagawa University, Hiratsuka, Japan.
Ushimado Marine Institute (UMI), Faculty of Environmental, Life, Natural Science and Technology, Okayama University, Okayama, Japan.
J Neuroendocrinol. 2023 Sep;35(9):e13324. doi: 10.1111/jne.13324. Epub 2023 Jul 29.
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.
控制社会性行为的神经肽能机制由大脑和脊髓广泛分布区域中的复杂神经元回路系统组成。在机体水平上，现在越来越清楚的是，除了神经元回路的激活外，“激素调节”也起着重要作用。腰骶脊髓中的胃泌素释放肽（GRP）系统是控制大鼠阴茎反射的神经回路的重要组成部分，这些回路通常被称为“脊髓射精发生器（SEG）”。催产素长期以来被认为是一种神经垂体激素，现在已知它参与哺乳动物社会性行为的调节，范围从社会联系到共情。然而，SEG神经元与下丘脑 - 脊髓催产素系统之间的功能相互作用仍不清楚。已知催产素主要在下丘脑神经元中合成，并从垂体后叶释放到循环中。催产素也从神经元的树突释放到下丘脑，在那里它们通过非突触性容积传递在社会行为中发挥重要作用。由于催产素最常见的功能是调节包括分娩、射乳和母性行为在内的女性生殖功能，催产素常被认为是一种“女性”激素。然而，有证据表明，一组小细胞催产素神经元投射到脊髓下部并控制大鼠的雄性性功能。在本报告中，我们综述了SEG神经元与下丘脑 - 脊髓催产素系统之间的功能相互作用以及这些神经肽对雄性性行为的影响。此外，我们讨论了最近发现的催产素在脊髓中的局部“容积传递”作用。我们研究的结果表明，新发现的“催产素介导的脊髓对雄性性功能的控制”可能有助于治疗勃起和射精功能障碍。
