Silwal Prabhisha, Singhal Pratyaksh, Senecal Joanne Mm, Senecal Julie Em, Lynn Bruce D, Nagy James I
Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada.
Int J Physiol Pathophysiol Pharmacol. 2024 Jun 15;16(3):55-76. doi: 10.62347/OGWV9376. eCollection 2024.
Sexually dimorphic spinal motoneurons (MNs) in the dorsomedial nucleus (DMN) and dorsolateral nucleus (DLN) as well as those in the cremaster nucleus are involved in reproductive behaviours, and the cremaster nucleus additionally contributes to testicular thermoregulation. It has been reported that MNs in DMN and DLN are extensively linked by gap junctions forming electrical synapses composed of connexin36 (Cx36) and there is evidence that subpopulation of MNs in the cremaster nucleus are also electrically coupled by these synapses.
We used immunofluorescence methods to detect enhanced green fluorescent protein (eGFP) reporter for Cx36 expression in these motor nuclei.
We document in male mice that about half the MNs in each of DMN and DLN express eGFP, while the remaining half do not. Further, we found that the eGFP vs. eGFP subsets of MNs in each of these motor nuclei innervate different target muscles; eGFP MNs in DMN and DLN project to sexually dimorphic bulbocavernosus and ischiocavernosus muscles, while the eGFP subsets project to sexually non-dimorphic anal and external urethral sphincter muscles. Similarly, eGFP vs. eGFP cremaster MNs were found to project to anatomically distinct portions of the cremaster muscle. By immunofluorescence, nearly all motoneurons in both DMN and DLN displayed punctate labelling for Cx36, including at eGFP/eGFP, eGFP/eGFP and eGFP/eGFP cell appositions.
Most if not all motoneurons in DMN and DLN are electrically coupled, including sexually dimorphic and non-dimorphic motoneurons with each other, despite absence of eGFP reporter in the non-dimorphic populations in these nuclei that have selective projections to sexually non-dimorphic target muscles.
位于背内侧核（DMN）和背外侧核（DLN）的性二态性脊髓运动神经元以及提睾肌核中的运动神经元参与生殖行为，提睾肌核还对睾丸温度调节起作用。据报道，DMN和DLN中的运动神经元通过由连接蛋白36（Cx36）组成的缝隙连接广泛相连，形成电突触，并且有证据表明提睾肌核中的部分运动神经元亚群也通过这些突触进行电耦合。
我们使用免疫荧光方法检测这些运动核中Cx36表达的增强绿色荧光蛋白（eGFP）报告基因。
我们在雄性小鼠中发现，DMN和DLN中各约一半的运动神经元表达eGFP，而另一半不表达。此外，我们发现这些运动核中每个核的eGFP与非eGFP运动神经元亚群支配不同的靶肌肉；DMN和DLN中的eGFP运动神经元投射到性二态性的球海绵体肌和坐骨海绵体肌，而非eGFP亚群投射到性非二态性的肛门和尿道外括约肌。同样，发现eGFP与非eGFP提睾肌运动神经元投射到提睾肌的不同解剖部位。通过免疫荧光，DMN和DLN中的几乎所有运动神经元都显示出Cx36的点状标记，包括在eGFP/非eGFP、非eGFP/eGFP和eGFP/eGFP细胞邻接处。
DMN和DLN中的大多数（如果不是全部）运动神经元是电耦合的，包括性二态性和非二态性运动神经元之间，尽管这些核中对性非二态性靶肌肉有选择性投射的非二态性群体中没有eGFP报告基因。
