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Neurol Sci. 2014 Sep;35(9):1421-7. doi: 10.1007/s10072-014-1774-9. Epub 2014 Apr 10.

Connections between EM2- and SP-containing terminals and GABAergic neurons in the mouse spinal dorsal horn.

Author information

1
Department of Anatomy, Histology and Embryology, Basic Medical College, Fujian Medical University, Fuzhou, 350004, China.

Abstract

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.

PMID:
24718557
DOI:
10.1007/s10072-014-1774-9
[Indexed for MEDLINE]

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