That prospect is a long way off, says Lique M. Coolen, assistant professor of cell biology, neurobiology, and anatomy at the University of Cincinnati, lead author of a report on the finding in the journal Science. A lot more work must be done, starting with studies to determine whether the same cell clusters exist in the human spinal cord.
Still, finding the center in any animal is important, she says. "We did know that something in the spinal cord triggered ejaculation, but we didn't know where the center is located," Coolen says. "Now we have found the anatomical site, and we can investigate the chemical signals that activate the cells and the chemical signals that the cells use to relay information to the brain."The Cincinnati researchers are starting to look for the same cells in samples of human spinal cord tissue. There is good reason to expect that they will be there, Coolen says, because "so far, every study of sexual function in animals has been found to be true in humans."
A first step will be to identify all the chemical signals that go into and out of the rat spinal cord cells. Once they are identified, the same chemicals can be sought in the human tissue samples.
"Hopefully, at some point we may be able to use this information to treat ejaculation dysfunction, such as premature ejaculation, but that is very far off," Coolen says.
The report is "exciting stuff" and "a good, positive first step," says David Rowland, professor of psychology at Valparaiso University in Indiana, who is doing research on ejaculation problems in men.
"It could be relevant to human problems, especially if there can be ways to sustain or enhance the activity of the neural cells in a noninvasive way," Rowland says. "Perhaps one could develop a pharmacological, site-specific treatment. If so, there is great value in knowing the location of these cells."
The specific clusters have been named LSt, or lumbar spinothalamic cells, after their site in the spinal cord. They were identified in a series of tests looking for cells that were activated in relation to ejaculation, but not with other aspects of the male rats' sexual behavior.
In a final test, the LSt cells were deactivated in male rats that were put in cages with sexually receptive females. The animals went through a sexual performance, but studies of the female rats afterward showed that the males had not ejaculated.
In humans, failure to ejaculate properly can result in inadequate delivery of sperm to the vaginal canal, so that fertilization does not take place. One of the most common problems, premature ejaculation, now is treated primarily by behavioral modification.
The finding could have implication for both sexes, Coolen says. "These cells also exist in female rats, so we want to find out what their function is in females," she says.
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