Distribution and ultrastructure of tachykinin-like immunoreactivity in the frog (Rana esculenta) spinal cord, notably, the dorsal horn.
Tachykinins are involved in pain transmission at the spinal level. In frog, at least four tachykinins [TK] have been isolated from the brain, but their organization in the dorsal horn of the spinal cord is still poorly known. We have reexamined TK distribution by immunocytochemistry using an antibody recognizing the sequence common to all tachykinins in the spinal cord and dorsal root ganglia of the green frog Rana esculenta. A dense tachykinin-like immunoreactivity (TK-LI) was observed in the dorsolateral fasciculus or Lissauer's tract running ventromedial to the entry of the dorsal root and in numerous small and medium-sized dorsal root ganglion cells showing a primary afferent origin for part of TK-LI of the dorsal horn. The observation of numerous cell bodies in the dorsal horn, in addition, suggested a local or propriospinal origin. One group of cells was localized at the entrance of the Lissauer's tract TK-LI fibers into the dorsal horn, and another group was localized in the upper dorsal horn, a region with a low density of TK-LI fibers. It was suggested that the latter group may correspond to neurokinin B. Electron microscopic examination of the Lissauer's tract showed numerous immunoreactive axons, some located at the center of glomerular-like arrangements, suggesting that the information brought by these fibers may be transmitted and most probably modulated before their entry in the dorsal horn. In conclusion, the functional organization of tachykinins in the frog spinal cord seems to be similar to that of mammals, albeit with a different morphological organization.
Departement de Neurobiologie des Signaux Intercellulaires, Institut des Neurosciences, CNRS UMR 7624, Université Pierre et Marie Curie, 75252 Paris Cedex 05, France.
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Salio
J
J
Fischer
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Wijkhuisen
M F
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Franzoni
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Conrath
D000818:Animals; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D011893:Rana esculenta / Q000378:metabolism*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D015320:Tachykinins / Q000378:metabolism*; D014018:Tissue Distribution
D015320:Tachykinins