Activation of MAP kinase in lumbar spinothalamic cells is required for ejaculation.
BACKGROUND
Ejaculation is a reflex controlled by a spinal ejaculation generator located in the lumbosacral spinal cord responsible for the coordination of genital sensory with autonomic and motor outputs that regulate ejaculation. In the male rat, a population of lumbar spinothalamic cells (LSt cells) comprises an essential component of the spinal ejaculation generator. LSt cells are activated with ejaculation, but the nature of the signal transduction pathways involved in this activation is unknown. Moreover, it is unknown if LSt cell activation is required for expression of ejaculation.


OBJECTIVE
The current study tested the hypothesis that ejaculatory reflexes are triggered via activation of the mitogen-activated protein (MAP) kinase signaling pathway in the LSt cells.


METHODS
Expression of phosphorylated extracellular signal-related kinases 1 and 2 (pERK) was investigated following mating behavior, or following ejaculation induced by electrical stimulation of the dorsal penile nerve (DPN) in anesthetized, spinalized male rats. Next, the effects of intrathecal or intraspinal delivery of Mitogen-activated protein/extracellular signal-regulated kinase (MEK) inhibitor U0126 on DPN stimulation-induced ejaculation was examined.


METHODS
Expression of pERK in LSt cells and associated areas was analyzed. Electromyographic recordings of the bulbocavernosus muscle were recorded in anesthetized, spinalized rats.


RESULTS
Results indicate that the MAP kinase signaling pathway is activated in LSt cells following ejaculation in mating animals or induced by DPN stimulation in anesthetized, spinalized animals. Moreover, ERK activation in LSt cells is an essential trigger for ejaculation, as DPN stimulation-induced reflexes were absent following administration of MEK inhibitor in the L3-L4 spinal area.


CONCLUSIONS
These data provide insight into the nature of the signal transduction pathways involved in the activation of ejaculation through LSt cells. The data demonstrate that ERK activation in LSt cells is essential for ejaculation and contribute to a more detailed understanding of the spinal generation of ejaculation.
Department of Anatomy and Cell Biology, The University of Western Ontario, London, Canada.
Michael D
MD
Staudt
Cleusa V R
CV
de Oliveira
Michael N
MN
Lehman
Kevin E
KE
McKenna
Lique M
LM
Coolen
D000818:Animals; D003307:Copulation / Q000502:physiology*; D004542:Ejaculation / Q000502:physiology*; D004576:Electromyography; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012726:Sexual Behavior, Animal / Q000502:physiology; D013116:Spinal Cord / Q000201:enzymology; D013133:Spinothalamic Tracts / Q000201:enzymology*
D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1