Truitt WA, Stanton LA, Coolen LM (2001) Targeted lesions of Substance P receptor cells in L3-4 lumbar spinal cord severely impair male ejaculatory behavior. Neuroscience 2001 Abstracts 958.18. Society for Neuroscience, San Diego, CA.
Summary: Previously we demonstrated the existence of a spinothalamic pathway in the male rat where neural activation is specifically induced by ejaculation. This pathway consists of the parvocellular subparafascicular thalamic nucleus (SPFp) and the neurons projecting to the SPFp that are located in the lumbar spinal cord, specifically in laminae 10 and 7 of segments L3-L4. This neuron population coexpresses galanin (Gal) and substance P receptors (SPR). To test the hypothesis that these cells relay sensory information related to ejaculation, these neurons were lesioned by targeting the SPR with the neurotoxin SSP-saporin, a high affinity analogue of substance P conjugated to the ribosome inhibitor saporin. SSP-saporin (4 ng/µl) or an equal concentration of unconjugated saporin was injected bilaterally into L3-L4 region in either sexually experienced or naïve male Sprague Dawley rats (n=5 each). Sexual behavior was tested weekly, starting ten days following surgery. Following the sixth behavioral test, rats were sacrificed and spinal cord tissue was immunostained for GAL, SPR, or NeuN to assess specific and nonspecific tissue damage. In rats injected with unconjugated saporin, the Gal/SPR cell population was intact and sexual behavior was not altered. In contrast, in rats receiving SSP-saporin, Gal/SPR cell population was significantly decreased (77%) or absent. Moreover, SSP-saporin lesions severely disrupted ejaculatory behavior. Interestingly, display of mounts and intromissions remained intact. These results suggest that Gal/SPR cells in laminae 10 and 7 of L3-4 lumbar spinal cord may be essential for male ejaculatory behavior.
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