title: Morphological evidence for a neurotensinergic periaqueductal gray-rostral ventromedial medulla-spinal dorsal horn descending pathway in rat.
abstract: Neurotensin (NT) is an endogenous neuropeptide that exerts potent opioid-independent analgesic effects, most likely via the type 2 NT receptor (NTR2). Previous morphological and electrophysiological studies suggested that the NT-NTR2 system is primarily localized in structures that constitute the descending pain control pathway, such as the periaqueductal gray (PAG), the rostral ventromedial medulla (RVM), and the spinal dorsal horn (SDH). However, relevant morphological evidence for this neurotensinergic (NTergic) circuit is lacking. Thus, the aim of the present study was to morphologically elucidate the potential sites and connections in the NT-NTR2 system that are involved in the descending pain control pathway. Based on light and electron microscopy combined with anterograde and retrograde tracing, we found evidence that NTR2-immunoreactive (IR) neurons in the RVM receive NT-IR projections originating from the PAG; express NT, serotonin (5-HT), or both; and send projections that terminate in laminae I and II of the SDH. These results suggest that NTR2 may contribute to pain control by binding to NT in the PAG-RVM-SDH pathway. In conclusion, our data provide morphological evidence for an NTergic PAG-RVM-SDH pathway, implicating novel mechanisms of NT-induced analgesia.
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Yu-Peng
authors.initials: YP
authors.lastname: Feng
authors.affiliation: Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Meng
authors.affiliation: Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China.
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Wu
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Jin-Shan
authors.initials: JS
authors.lastname: Zhang
authors.affiliation: Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China.
authors.forename: Yun-Qing
authors.initials: YQ
authors.lastname: Li
keywords: NTR2; analgesia; neurotensin; nociception; periaqueductal gray matter; rostral ventromedial medulla (RVM)