Oxytocin Influences Male Sexual Activity via Non-synaptic Axonal Release in the Spinal Cord

Takumi Oti, Keita Satoh, Daisuke Uta, Junta Nagafuchi, Sayaka Tateishi, Ryota Ueda, Keiko Takanami, Larry J. Young, Antony Galione, John F. Morris, Tatsuya Sakamoto, Hirotaka Sakamoto

Research output: Contribution to journalArticlepeer-review

Abstract

Oxytocinergic neurons in the paraventricular nucleus of the hypothalamus that project to extrahypothalamic brain areas and the lumbar spinal cord play an important role in the control of erectile function and male sexual behavior in mammals. 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).” We have examined the functional interaction between the SEG neurons and the hypothalamo-spinal oxytocin system in rats. Here, we show that SEG/GRP neurons express oxytocin receptors and are activated by oxytocin during male sexual behavior. Intrathecal injection of oxytocin receptor antagonist not only attenuates ejaculation but also affects pre-ejaculatory behavior during normal sexual activity. Electron microscopy of potassium-stimulated acute slices of the lumbar cord showed that oxytocin-neurophysin-immunoreactivity was detected in large numbers of neurosecretory dense-cored vesicles, many of which are located close to the plasmalemma of axonal varicosities in which no electron-lucent microvesicles or synaptic membrane thickenings were visible. These results suggested that, in rats, release of oxytocin in the lumbar spinal cord is not limited to conventional synapses but occurs by exocytosis of the dense-cored vesicles from axonal varicosities and acts by diffusion—a localized volume transmission—to reach oxytocin receptors on GRP neurons and facilitate male sexual function.

Original languageEnglish
Pages (from-to)103-114.e5
JournalCurrent Biology
Volume31
Issue number1
DOIs
Publication statusPublished - Jan 11 2021

Keywords

  • gastrin-releasing peptide
  • localized volume transmission
  • male sexual activity
  • oxytocin
  • spinal cord
  • spinal ejaculation generator

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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