Connections between EM2- and SP-containing terminals and GABAergic neurons in the mouse spinal dorsal horn.
Endomorphin-2 (EM2) demonstrates a potent antinociceptive effect in pain modulation. To investigate the potential interactions of EM2- and substance P (SP)-containing primary afferents and γ-amino butyric acid (GABA)-containing interneurons in lamina II in nociceptive transmission, connections between EM2- and SP-containing terminals and GABAergic neurons in the spinal dorsal horn were studied. Double-immunofluorescent labeling showed that approximately 62.3 % of EM2-immunoreactive neurons exhibited SP-immunostaining, and 76.9 % of SP-immunoreactive neurons demonstrated EM2-immunoreactivities in the dorsal root ganglion (DRG). Dense double-labeled EM2- and SP-immunoreactivities were mainly observed in lamina II of the lumbar dorsal horn. Furthermore, triple-immunofluorescent labeling results revealed that EM2 and SP double-labeled terminals overlapped with GABAergic neurons. Immuno-electron microscopy confirmed that the EM2- or SP-immunoreactive terminals formed synapses with GABA-immunoreactive dendrites in lamina II of the lumbar dorsal horn. During noxious information transmission induced by formalin plantar injection, GABAergic neurons expressing FOS in their nuclei were contacted with EM2- or SP-immunoreactive terminals. These results suggest that the interactions between EM2- and SP-containing terminals and GABAergic interneurons in the lamina II influence pain transmission and modulation in the spinal dorsal horn.
Department of Anatomy, Histology and Embryology, Basic Medical College, Fujian Medical University, Fuzhou, 350004, China.
Dao-Shu
DS
Luo
Jing
J
Huang
Yu-Lin
YL
Dong
Zhen-Yu
ZY
Wu
Yan-Yan
YY
Wei
Ya-Cheng
YC
Lu
Ya-Yun
YY
Wang
Yuchio
Y
Yanagawa
Sheng-Xi
SX
Wu
Wei
W
Wang
Yun-Qing
YQ
Li
D000818:Animals; D059330:GABAergic Neurons / Q000166:cytology* / Q000378:metabolism*; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron; D009842:Oligopeptides / Q000378:metabolism*; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D066148:Spinal Cord Dorsal Horn / Q000166:cytology*; D013373:Substance P / Q000378:metabolism*
D009842:Oligopeptides; D016761:Oncogene Proteins v-fos; D049452:Green Fluorescent Proteins; D013373:Substance P; C105294:endomorphin 2; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1