Neurochemical Properties of the Synapses in the Pathways of Orofacial Nociceptive ReflexesReportar como inadecuado

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The brainstem premotor neurons of the facial nucleus VII and hypoglossal XII nucleus can integrate orofacial nociceptive input from the caudal spinal trigeminal nucleus Vc and coordinate orofacial nociceptive reflex ONR responses. However, the synaptoarchitectures of the ONR pathways are still unknown. In the current study, we examined the distribution of GABAergic premotor neurons in the brainstem local ONR pathways, their connections with the Vc projections joining the brainstem ONR pathways and the neurochemical properties of these connections. Retrograde tracer fluoro-gold FG was injected into the VII or XII, and anterograde tracer biotinylated dextran amine BDA was injected into the Vc. Immunofluorescence histochemical labeling for inhibitory-excitatory neurotransmitters combined with BDA-FG tracing showed that GABAergic premotor neurons were mainly distributed bilaterally in the ponto-medullary reticular formation with an ipsilateral dominance. Some GABAergic premotor neurons made close appositions to the BDA-labeled fibers coming from the Vc, and these appostions were mainly distributed in the parvicellular reticular formation PCRt, dorsal medullary reticular formation MdD, and supratrigeminal nucleus Vsup. We further examined the synaptic relationships between the Vc projecting fibers and premotor neurons in the VII or XII under the confocal laser-scanning microscope and electron microscope, and found that the BDA-labeled axonal terminals that made asymmetric synapses on premotor neurons showed vesicular glutamate transporter 2 VGluT2 like immunoreactivity. These results indicate that the GABAergic premotor neurons receive excitatory neurotransmission from the Vc and may contribute to modulating the generation of the tonic ONR.

Autor: Yu-lin Dong , Wen Wang , Hui Li, Zhi-hong Li, Fu-xing Zhang, Ting Zhang, Ya-cheng Lu, Jin-lian Li , Sheng-xi Wu , Yun-qing Li



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