Rojas-Piloni Gerardo, López-Hidalgo Mónica, Martínez-Lorenzana Guadalupe, Rodríguez-Jiménez Javier, Condés-Lara Miguel
Departamento de Neurobiología del Desarrollo y Neurofisiología, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-Juriquilla, Querétaro, Mexico.
Brain Res. 2007 Mar 16;1137(1):69-77. doi: 10.1016/j.brainres.2006.12.045. Epub 2006 Dec 22.
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 Adelta, Abeta, and C-fibers were studied. Suspected interneurons that are typically silent and lack peripheral receptive field responses were also analyzed. PVN electrical stimulation inhibits Adelta (-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 Adelta and C-fiber activity without affecting Abeta fibers. We conclude that Adelta and C-fibers receive a presynaptic inhibition mediated by GABA.
在麻醉大鼠中，我们测试了接受伤害性输入的背角神经元的单位活动是否受到下丘脑室旁核（PVN）电刺激的调节。对L3-L4节段的背角神经元进行电生理定位，使我们能够选择对位于左后爪趾部区域的感受野有反应的细胞。背角神经元根据其对周围刺激的反应特性进行分类。研究了对周围感受野电刺激有反应并呈现Aδ、Aβ和C纤维突触输入的广动力范围（WDR）细胞。还分析了通常沉默且缺乏周围感受野反应的疑似中间神经元。PVN电刺激抑制了WDR细胞中Aδ（-55.0±10.2%）、C纤维（-73.1±6.7%）和放电后（-75.0±8.9%）的周围激活，并且沉默中间神经元被激活。因此，最后这种类型的中间神经元被称为PVN-ON细胞。在WDR细胞中，鞘内注射特异性催产素拮抗剂或荷包牡丹碱可阻断PVN刺激引起的周围反应抑制。然而，相同的特异性催产素拮抗剂可阻断PVN-ON细胞的激活，但荷包牡丹碱则不能。我们的结果表明，PVN刺激通过由GABA能PVN-ON细胞介导的下行催产素能通路抑制WDR神经元中伤害性外周诱发反应。我们讨论了PVN电刺激选择性抑制Aδ和C纤维活动而不影响Aβ纤维的观察结果。我们得出结论，Aδ和C纤维接受由GABA介导的突触前抑制。
