GABA-mediated oxytocinergic inhibition in dorsal horn neurons by hypothalamic paraventricular nucleus stimulation
- 作者：Gerardo Rojas-Piloni ; Mó ; nica Ló ; pez-Hidalgo ; Guadalupe Martí ; nez-Lorenzana ; Javier Rodrí ; guez-Jimé ; nez ; Miguel Condé ; s-Lara
- 关键词：Pain ; Antinociception ; Presynaptic inhibition ; Endogenous analgesia
- 刊名：Brain Research
- 出版年：2007
- 期刊代码：8_00068993
- 类别：neu
- 出版时间：16 March 2007
- 卷：1137
- 期：Complete
- 页码：69-77
- 文件大小：714 K
摘要
In anaesthetized rats, we tested whether the unit activity of dorsal horn neurons that receive nociceptive input is modulated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN). An electrophysiological mapping of dorsal horn neurons at L3–L4 let us choose cells responding to a receptive field located in the toes region of the left hindpaw. Dorsal horn neurons were classified according to their response properties to peripheral stimulation. Wide Dynamic Range (WDR) cells responding to electrical stimulation of the peripheral receptive field and presenting synaptic input of Aδ, Aβ, and C-fibers were studied. Suspected interneurons that are typically silent and lack peripheral receptive field responses were also analyzed. PVN electrical stimulation inhibits Aδ (− 55.0 ± 10.2%), C-fiber (− 73.1 ± 6.7%), and post-discharge (− 75.0 ± 8.9%) peripheral activation in WDR cells, and silent interneurons were activated. So, this last type of interneuron was called a PVN-ON cell. In WDR cells, the inhibition of peripheral responses caused by PVN stimulation was blocked by intrathecal administration of a specific oxytocin antagonist or bicuculline. However, PVN-ON cell activation was blocked by the same specific oxytocin antagonist, but not by bicuculline. Our results suggest that PVN stimulation inhibits nociceptive peripheral-evoked responses in WDR neurons by a descending oxytocinergic pathway mediated by GABAergic PVN-ON cells. We discuss our observation that the PVN electrical stimulation selectively inhibits Aδ and C-fiber activity without affecting Aβ fibers. We conclude that Aδ and C-fibers receive a presynaptic inhibition mediated by GABA.