Origins of GABA(B) receptor-like immunoreactive terminals in the rat spinal dorsal horn.
By means of immunohistochemistry for gamma-aminobutyric acid receptor B subtype (GABA(B)R), the origins of GABA(B)R-like immunoreactive (GABA(B)R-LI) terminals in the rat spinal dorsal horn were investigated. After dorsal root rhizotomy and/or spinal cord hemisection, the densities of GABA(B)R-LI terminals were remarkably depleted in the ipsilateral superficial dorsal horn of relevant segments, whereas GABA(B)R-LI neurons and sparsely distributed GABA(B)R-LI terminals remained. After injection of Fluoro-Gold (FG) into the left side of superficial lumbar dorsal horn, FG retrograde-labeled neurons were mainly observed in the ipsilateral rostral ventromedial medulla (RVM) and brainstem raphe nuclei. Some of the FG-labeled neurons, especially in the RVM, exhibited GABA(B)R-like immunoreactivity. Additionally, immunofluorescence histochemical double-staining revealed that the majority of GABA(B)R-LI neurons in the periaqueductal gray (PAG), RVM and brainstem raphe nuclei showed 5-hydroxytryptamine (5-HT)-like immunoreactivity. The present study morphologically proves that GABA(B)R-LI terminals in the spinal dorsal horn originate from peripheral afferents, intrinsic neurons and supraspinal structures; GABA(B)R and 5-HT co-exist in many neurons in the PAG, RVM and brainstem raphe nuclei. Considering that PAG, RVM, brainstem raphe nuclei and spinal dorsal horn are important structures involved in the pain modulation, we suggest that the descending pain modulation system might be mediated, at least in part, by GABA(B)R.
Yang
Kun
K
Department of Anatomy and K K Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, PR China.
Ma
Wen-Ling
WL
Feng
Yu-Peng
YP
Dong
Yuan-Xiang
YX
Li
Yun-Qing
YQ
D000344:Afferent Pathways / Q000378:metabolism / Q000473:pathology; D000818:Animals; D007150:Immunohistochemistry; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D020671:Posterior Horn Cells / Q000378:metabolism* / Q000473:pathology; D011903:Raphe Nuclei / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018080:Receptors, GABA-B / Q000378:metabolism*; D019051:Rhizotomy; D012701:Serotonin / Q000378:metabolism; D013904:Thoracic Vertebrae
D018080:Receptors, GABA-B; D012701:Serotonin