| Summary: | 博士 === 國立成功大學 === 基礎醫學研究所 === 101 === The nerve system based on different innervation can be divided into somatic and visceral system. The nerve system based different function also can be divided as sensory and motor system. Therefore, there are somatic sensory, somatic motor, visceral sensory and visceral motor systems. The major two pathways of somatic sensory system are spinothalamic tract and posterior column – medial lemniscal tract. The somatic motor innervation is from cortex to skeletal muscle via corticospinal tract. The somatic sensory and motor systems have direct neuronal connection called spinal reflex between each other. The visceral sensory system translates visceral afferent through spinothalamic tract, spinoreticular tract, vagus nerve and glossopharyngeal nerve. The visceral motor system regulates the function of visceral organs by activating sympathetic and parasympathetic systems. The autonomic system is the reflex from visceral sensory afferent directly activate visceral motor efferent. However, it is still not clear whether the somatic and visceral systems have neuronal connection. The previous study using neurogenic plasma extravasation method showed that uterine pain referred to the groin region through a neuronal mechanism (Wesselmann and Lai, 1997). But, the relay center of this pathway is still not clearly identified. Our study proposes to investigate the neuronal connection between specific somatic point and visceral organ. In the present study, bee venom was injected in the groin region to induce central Fos expression to map the sensory innervation of groin region. Pseudorabies virus (PrV), a transneuronal tracer, was injected in the uterus to identify the innervation of the uterus. Immunohistochemistry staining revealed that the fos expression and PrV infected double labeled neurons in the nucleus of solitary tract (NTS), the dorsal motor nucleus of vagus (DMX), and the paraventricular hypothalamic nucleus (PVN). These results suggest a somato-parasympathetic neuronal connection (groin-spinal dorsal horn-NTS/DMX-uterus) and a somato-sympathetic neuronal connection (groin-spinal dorsal horn-NTS-PVN-uterus). These two neuronal connections could be the pre-requisites to the neuronal basis of the somatovisceral reflex and also the neuronal mechanism of acupuncture. On the other hand, Fos expression and PrV infected double labeled neurons were mainly found in the T11, T12, T13, L1, S1 dorsal root ganglia, the nucleus of solitary tract (NTS), the other nuclei of brainstem, but not in the spinal dorsal horn. These results suggest the peripheral processes of the dichotomizing DRG neurons receiving sensory afferents either from the uterus or the groin region and the central process projects to the NTS. This morphological evidence demonstrates that the neuronal substrate of referred pain is the dichotomizing DRG neurons (the first order sensory neurons) and the NTS (the second order sensory neurons). These connections between somatic and visceral systems provide more understanding about the interaction of the nerve system.
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