Ectopic substance P-immunoreactive boutons are preferentially presynaptic to neurokinin-1 receptor immunoreactive dendrites in the spinal white matter of transgenic mice.
A recent immunocytochemical study has shown that substance P (SP) preferentially innervates targets expressing the neurokinin-1 receptor (NK-1r) in the superficial spinal dorsal horn of the rat. Based on these findings, we decided to further investigate the relationship between SP and the NK-1r in a transgenic mouse model in which SP fibres are ectopically located. Double-labelling immunocytochemistry at both the light and electron microscopic levels was performed to study the association between SP and the NK-1r in the spinal white matter of both control and transgenic mice. Light microscopy revealed NK-1r-immunoreactive (IR) dendrites in the white matter of the dorsolateral funiculus in both control and transgenic mice. In transgenic mice, but not in controls, SP-IR fibres were observed in close proximity to the NK-1r-IR dendrites in the white matter. At the ultrastructural level, SP-IR boutons were apposed to NK-1r-IR dendrites in the dorsolateral funiculus of transgenic mice, and a synapse was frequently observed as well. These results indicate that, even in conditions in which SP fibres are ectopically located, they still preferentially innervate targets expressing the NK-1r.
McLeod
A L
AL
Department of Pharmacology and Therapeutics, McGill University, 3655 Drummond St., Room 1325, Montreal, Quebec, Canada.
Julien
J P
JP
Cuello
A C
AC
Krause
J E
JE
Ribeiro-da-Silva
A
A
D000818:Animals; D003712:Dendrites / Q000737:chemistry*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D009412:Nerve Fibers / Q000737:chemistry; D018041:Receptors, Neurokinin-2 / Q000032:analysis*; D017661:Receptors, Presynaptic / Q000032:analysis*; D013116:Spinal Cord / Q000737:chemistry* / Q000648:ultrastructure; D013373:Substance P / Q000032:analysis*
D018041:Receptors, Neurokinin-2; D017661:Receptors, Presynaptic; D013373:Substance P