Previous study suggested that acupuncture may influence visceral function via the activation of the somatosensory neurons (Kim, et al., 2012). However, most researches focused on the physiological responses induced by acupuncture (Chao, et al., 1999, Peng, 2002, Sun and Yao, 1985). The purpose of our study is to investigate and provide the
33
morphological evidence of somatovisceral reflex and possible neuronal pathway of
acupuncture. Our result suggests that the PVN, NTS, and DMX could be the relay center of the somatovisceral reflex. The visceral organs usually receive sympathetic and
parasympathetic dual interacted and the interaction is antagonistic. Therefore, our study proved morphological evidence of both sympathetic and parasympathetic pathways of somatovisceral reflex between the groin A-shi point and the uterus (Fig. 10). The somato-parasympathetic pathway starts from the stimulation of the groin A-shi point, which activates neurons in the spinal dorsal horn. The signal in turn elicits noxious input to the NTS (Esteves, et al., 1993). Neurons in the NTS relay the information and project to the DMX (Norgren, 1978), which innervates the uterus through the vagus nerve
(Ortega-Villalobos, et al., 1990) (Fig. 10 A). The somato-sympathetic pathways from the neurons in the spinal dorsal horn project to the NTS (Esteves, et al., 1993) than direct connection to the PVN (Ter Horst, et al., 1989), it innervates the visceral organ through the sympathetic pre- and postganglionic neurons (Hosoya, et al., 1991) (Fig. 10 B). These complementary somato-sympathetic and -parasympathetic systems coincidentally match the concept of yin-yang theory in traditional Chinese medicine (Paton, et al., 2005, World Health Organization. Regional Office for the Western Pacific., 1993).
The present study provides the morphological evidences of the neuronal connection between somatic groin A-shi point and its corresponding visceral organ-uterus. Therefore,
34
we come up to the conclusion that the somato-sympathetic/-parasympathetic pathways are the morphological basis of somatovisceral reflex and also the neuronal substrate of
acupuncture pathways.
In conclusion, the study helps us better understanding the interaction between somatic and visceral system. The mechanism of somatovisceral reflex, acupuncture and referred pain are all involved the connection between somatic and visceral system. This study provides the morphological evidences of the pathways between somatic and visceral system.
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Figure 1
Fos expression neurons in dorsal root ganglia
A：Fos expression neuron (arrow) in T13 DRG (scale bar : 100um)
B：Fos expression neurons in T10-S1 DRG, T10(8.7±3.4), T11(5.0±1.5), T12(6.3±1.5), T13(7.9±3.4), L1(13.1±4.4), L2(5.4±1.9), L3(0.9±0.5), L4(0.±0.1), L6(5.1±2.1) and S1(10.3±4.6) (±SEM)
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Figure 2
Fos expression neurons in the spinal cord after bee venom injection in the left groin region (n =9) A: Neurons express Fos protein (arrow) in ipsilateral L2 spinal dorsal horn. B:
Higher magnification of Fos expression neurons in A (scale bar : 100um). C: Mean number of Fos expression neurons in T10 to S3 spinal segments (±SEM). *P＜0.05 D: Mean number of Fos expression neurons in lamina I to V of L2 spinal segment.
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40
Figure 3
Fos expression neurons (arrow) in the supraspinal area after bee venom injection in the left groin region (n=9). A: nucleus of solitary tract (NTS). B: locus coeruleus (LC),
parabrachial nucleus (PB) C: raphe pallidus nucleus (RPa). D: paraventricular
hypothalamic nucleus (PVN). E: lateral hypothalamic area. F: paraventricular thalamic nucleus (PV). 3 V: third ventricle; 4 V: fourth ventricle; D3 V: dorsal third ventricle; d:
dorsal; f: fornix; ic: internal capsule; l: lateral; m: medial; opt: optic tract; scp: superior cerebellar peduncle; v: ventral (scale bar : 100um).
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42
Table 1
Fos expression neurons in supraspinal area between saline and bee venom injection group.
(*：significant difference between saline group, p<0.1)
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Fig. 4
PrV infected neurons in dorsal root ganglia 7~8 days after PrV injection in left uterine horn A：PrV infected neuron (arrow) in L1 dorsal root ganglion
B：Mean of PrV infected neurons in T10~S1 dorsal root ganglia (±SEM)
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Figure 5
PrV-infected neurons in spinal cord after 6 to 8 d PrV-injection in the left uterine horn (n=8). A: PrV-infected neuron (arrow) in T12 spinal segment. B: Higher magnification of PrV-infected neuron in A (arrow) (scale bar : 100um) C: Mean number of PrV-infected neurons inT10 to S2 spinal segments (±SEM).
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Figure 6
PrV-infected neurons (arrow) in the supraspinal area after 7-8 d PrV injection in the left uterus horn (n=8). A: PrV-infected neurons in the NTS and DMX. B: PrV-infected neurons in the A5 noradrenaline cell group. C: PrV-infected neurons in the RPa and RMg. D:
PrV-infected neurons in the Gi. E: PrV-infected neurons in the PVN. 3 V: third ventricle;
AP: area postrema; DMX: motor nucleus of vagus; Gi: gigantocellular reticular nucleus;
Gr: gracile nucleus; NTS: nucleus of solitary tract; PVN: paraventricular hypothalamic nucleus; RPa: raphe pallidus nucleus; RMg: raphe magnus nucleus (scale bar : 100um).
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Table 2
PrV infected neurons in supraspinal area. (+：1-3 infected neurons, ++：4-8 infected neurons, +++：>9 infected neurons)
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Figure 7
Double labeled of Fos expression and PrV infected neurons in dorsal root ganglia Fos expression neurons (A, red), PrV infected neurons (B, green) and merged double labeled Fos expression and PrV infected neuron (C, yellow) in T11 DRG.
D：Percentage of Fos expression and PrV infected double dorsal root ganglion neurons (double labeled / PrV infected neurons) through T10-S1 spinal segment.
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50
Figure 8
Double-labeled neurons of Fos expression and PrV infection (n=8)
Fos expression neurons (A, red, arrow) in the PVN (A1), NTS (A2, A3) and DMX (A2, A4). PrV-infected neurons (B, green, arrow) in the PVN (B1), NTS (B2, B3) and DMX (B2, B4). Merged double labeling Fos expression and PrV-infected neurons (C, yellow, arrow) in the PVN (C1), NTS (C2, C3), and DMX (C2, C4) (scale bar : 1000um). D : The percentage of double labeled neurons in PVN, DMX and NTS between saline and bee venom injection groups (*:p<0.1)
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Figure 9
Diagram showing the peripheral process of dichotomizing DRG neurons receive afferents from both the uterus and groin. The central process of the dichotomizing DRG neurons projects to the NTS.
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Figure 10
Schematic drawing three neuronal pathway of somatovisceral reflex.
A：Somato-parasympathetic reflex pathway through the vagus nerve B：Somato-sympathetic reflex pathways through the NTS and PVN
DMX：dorsal motor nucleus of vagus DRG：dorsal root ganglia NTS：nucleus of solitary tract
SPN：sympathetic preganglionic neurons PVN：paraventricular hypothalamic nucleus Blue：somatic afferent Red：visceral efferent
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