title: Activation of NMDA receptors in lumbar spinothalamic cells is required for ejaculation.
abstract: BACKGROUND
  The sexual reflex ejaculation is controlled by a spinal ejaculation generator located in the lumbosacral spinal cord. A population of spinothalamic (LSt) neurons forms a key component of this generator, as manipulations of LSt cells either block or trigger ejaculation. However, it is currently unknown which afferent signals contribute to the activation of LSt cells and ejaculation.
  
  
  OBJECTIVE
  The current study tested the hypothesis that glutamate, via activation of N-Methyl-D-aspartic acid (NMDA) receptors in LSt cells, is a key regulator of ejaculation.
  
  
  METHODS
  Expression of phosphorylated NMDA receptor subunit 1 (NR1) was investigated following mating, or following ejaculation induced by electrical stimulation of the dorsal penile nerve (DPN) in anesthetized, spinalized male rats. Next, the effects of intraspinal delivery of NMDA receptor antagonist AP-5 on DPN stimulation-induced ejaculation were examined. Moreover, the ability of intraspinal delivery of NMDA to trigger ejaculation was examined. Finally, the site of action of NMDA was determined by studying effects of NMDA in male rats with LSt cell-specific lesions.
  
  
  METHODS
  Expression of NR1 and phosphorylated NR1 in LSt cells was analyzed. Electromyographic recordings of the bulbocavernosus muscle (BCM) were recorded in anesthetized, spinalized rats following stimulation of the DPN and delivery of AP-5 or NMDA.
  
  
  RESULTS
  Results indicate that the NR1 receptors are activated in LSt cells following ejaculation in mating animals or induced by DPN stimulation in anesthetized, spinalized animals. Moreover, NR1 activation in LSt cells is an essential trigger for rhythmic BCM bursting, as DPN stimulation-induced reflexes were absent following administration of NMDA receptor antagonist in the L3-L4 spinal area, and were triggered by NMDA. NMDA effects were dependent on intact LSt cells and were absent in LSt-lesioned males.
  
  
  CONCLUSIONS
  These results demonstrate that glutamate, via activation of NMDA receptors in LSt cells, is a key afferent signal for ejaculation.
authors.affiliation: The University of Western Ontario-Department of Anatomy and Cell Biology, London, Canada.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Staudt
authors.forename: Cleusa V R
authors.initials: CV
authors.lastname: de Oliveira
authors.forename: Michael N
authors.initials: MN
authors.lastname: Lehman
authors.forename: Kevin E
authors.initials: KE
authors.lastname: McKenna
authors.forename: Lique M
authors.initials: LM
authors.lastname: Coolen
mesh_terms: D000818:Animals; D004542:Ejaculation / Q000187:drug effects*; D004558:Electric Stimulation; D018698:Glutamic Acid / Q000187:drug effects*; D008161:Lumbosacral Region; D008297:Male; D010413:Penis; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*; D012018:Reflex / Q000187:drug effects; D012726:Sexual Behavior, Animal; D013133:Spinothalamic Tracts / Q000187:drug effects*
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid