Topographical relation between serotonin-containing paraneurons and peptidergic neurons in the intestine and urethra.
Luminal stimulation of enterochromaffin (EC) cells is known to cause their release of serotonin which in turn may induce a variety of reflexes via mucosal intrinsic neurons. To morphologically support this idea, the present study demonstrates a close topographical relationship between EC cells and nerves, using whole-mount preparations. Beaded nerve fibers containing vasoactive intestinal polypeptide (VIP) were observed in close proximity to serotonin-immunoreactive EC cells in the small and large intestines of the rat and guinea pig; in whole-mount preparations, the VIP nerve fibers appeared to underlie EC cells. This finding correlates with the physiological datum that the intra-arterial infusion of serotonin causes VIP release from the intestine. Canine urethral serotonin cells, a counterpart of the intestinal EC cells, were shown to contact intraepithelial nerves immunoreactive for calcitonin gene-related peptide. The neuroparaneuronal connection in the urethra may play an important role in the serotonin-evoked urethrogenital reflex. Intestinal and urethral serotonin-containing paraneurons, which are sensory in nature, may release serotonin in response to luminal stimuli, and directly activate adjacent peptidergic neurons to initiate the reflex arcs.
Iwanaga
T
T
Department of Anatomy, Niigata University School of Medicine, Japan.
Han
H
H
Hoshi
O
O
Kanazawa
H
H
Adachi
I
I
Fujita
T
T
D000818:Animals; D004759:Enterochromaffin Cells / Q000378:metabolism; D004847:Epithelial Cells; D004848:Epithelium / Q000294:innervation / Q000378:metabolism; D006168:Guinea Pigs; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology / Q000294:innervation*; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D015398:Signal Transduction; D014521:Urethra / Q000166:cytology / Q000294:innervation* / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D012701:Serotonin; D014660:Vasoactive Intestinal Peptide