Stress-induced analgesia (SIA) is an evolutionarily conserved phenomenon during stress. Neuropeptide S (NPS), orexins, substance P, glutamate and endocannabinoids are known to be involved in stress and/or SIA, however their causal links remain unclear. Here, we reveal an unprecedented sequential cascade involving these mediators in the lateral hypothalamus (LH) and ventrolateral periaqueductal gray (vlPAG) using a restraint stress-induced SIA model. Male C57BL/6 mice of 8–12 week-old were subjected to intra-cerebroventricular (i.c.v.) and/or intra-vlPAG (i.pag.) microinjection of NPS, orexin-A or substance P alone or in combination with selective antagonists of NPS receptors (NPSRs), OX1 receptors (OX1Rs), NK1 receptors (NK1Rs), mGlu5 receptors (mGlu5Rs) and CB1 receptors (CB1Rs), respectively. Antinociceptive effects of these mediators were evaluated via the hot-plate test. SIA in mice was induced by a 30-min restraint stress. NPS levels in the LH and substance P levels in vlPAG homogenates were compared in restrained and unrestrained mice. NPS (i.c.v., but not i.pag.) induced antinociception. This effect was prevented by i.c.v. blockade of NPSRs. Substance P (i.pag.) and orexin-A (i.pag.) also induced antinociception. Substance P (i.pag.)-induced antinociception was prevented by i.pag. Blockade of NK1Rs, mGlu5Rs or CB1Rs. Orexin-A (i.pag.)-induced antinociception has been shown previously to be prevented by i.pag. blockade of OX1Rs or CB1Rs, and here was prevented by NK1R or mGlu5R antagonist (i.pag.). NPS (i.c.v.)-induced antinociception was prevented by i.pag. blockade of OX1Rs, NK1Rs, mGlu5Rs or CB1Rs. SIA has been previously shown to be prevented by i.pag. blockade of OX1Rs or CB1Rs. Here, we found that SIA was also prevented by i.c.v. blockade of NPSRs or i.pag. blockade of NK1Rs or mGlu5Rs. Restrained mice had higher levels of NPS in the LH and substance P in the vlPAG than unrestrained mice. These results suggest that, during stress, NPS is released and activates LH orexin neurons via NPSRs, releasing orexins in the vlPAG. Orexins then activate OX1Rs on substance P-containing neurons in the vlPAG to release substance P that subsequently. Activates NK1Rs on glutamatergic neurons to release glutamate. Glutamate then activates perisynaptic mGlu5Rs to initiate the endocannabinoid retrograde inhibition of GABAergic transmission in the vlPAG, leading to analgesia.

中文翻译：

---

由OX ₁，NK ₁，mGlu ₅和CB ₁受体介导的神经肽S启动的级联反应：在应激诱导的镇痛中起关键作用

应激诱导的镇痛（SIA）是应激期间的进化保守现象。已知神经肽S（NPS），食欲肽，P物质，谷氨酸和内源性大麻素与压力和/或SIA有关，但其因果关系仍不清楚。在这里，我们揭示了一个空前的顺序级联反应，涉及使用约束应激诱导的SIA模型在下丘脑外侧（LH）和腹侧导水管周围灰色（vlPAG）中的这些介体。对8-12周大的雄性C57BL / 6小鼠进行脑室内（icv）和/或vlPAG（i.pag。）显微注射NPS，orexin-A或P物质单独注射或与选择性拮抗剂联合注射NPS受体（NPSRs），OX1受体（OX1Rs），NK1受体（NK1Rs），mGlu5受体（mGlu5Rs）和CB1受体（CB1Rs）。通过热板试验评估了这些介体的抗伤害感受作用。30分钟的束缚压力诱发小鼠SIA。比较了受约束和不受约束的小鼠的LH中的NPS水平和vlPAG匀浆中的P物质水平。NPS（icv，但不是i.pag。）诱导抗伤害感受。icv阻止NPSR阻止了这种作用。P（i.pag。）物质和orexin-A（i.pag。）也诱导抗伤害感受。i.pag预防了物质P（i.pag。）诱导的镇痛作用。NK1R，mGlu5R或CB1R的封锁。以前已显示由Orexin-A（i.pag。）诱导的抗伤害感受可被i.pag预防。OX1Rs或CB1Rs的阻断，在这里被NK1R或mGlu5R拮抗剂（i.pag。）阻止。i.pag可防止NPS（icv）诱导的抗伤害感受。阻断OX1R，NK1R，mGlu5R或CB1R。先前已显示i.pag可以防止SIA。阻断OX1R或CB1R。在这里，我们发现icv阻止NPSR或i.pag也可以预防SIA。NK1Rs或mGlu5Rs的封锁。与未受约束的小鼠相比，受约束的小鼠的LH中的NPS和vlPAG中的P物质含量更高。这些结果表明，在压力下，NPS被释放并通过NPSR激活LH食欲素神经元，从而在vPAG中释放食欲素。然后，食欲素激活vlPAG中含P物质的神经元上的OX1Rs，随后释放P物质。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。我们发现icv阻止NPSR或i.pag也可以预防SIA。NK1Rs或mGlu5Rs的封锁。与未受约束的小鼠相比，受约束的小鼠的LH中的NPS和vlPAG中的P物质含量更高。这些结果表明，在压力下，NPS被释放并通过NPSR激活LH食欲素神经元，从而在vPAG中释放食欲素。然后，食欲素激活vlPAG中含P物质的神经元上的OX1Rs，随后释放P物质。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。我们发现icv阻止NPSR或i.pag也可以预防SIA。NK1Rs或mGlu5Rs的封锁。与未受约束的小鼠相比，受约束的小鼠的LH中的NPS和vlPAG中的P物质含量更高。这些结果表明，在压力下，NPS被释放并通过NPSR激活LH食欲素神经元，从而在vPAG中释放食欲素。然后，食欲素激活vlPAG中含P物质的神经元上的OX1Rs，随后释放P物质。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。与未受约束的小鼠相比，受约束的小鼠的LH中的NPS和vlPAG中的P物质含量更高。这些结果表明，在压力下，NPS被释放并通过NPSR激活LH食欲素神经元，从而在vPAG中释放食欲素。然后，食欲素激活vlPAG中含P物质的神经元上的OX1Rs，随后释放P物质。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。与未受约束的小鼠相比，受约束的小鼠的LH中的NPS和vlPAG中的P物质含量更高。这些结果表明，在压力下，NPS被释放并通过NPSR激活LH食欲素神经元，从而在vPAG中释放食欲素。然后，食欲素激活vlPAG中含P物质的神经元上的OX1Rs，随后释放P物质。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。激活谷氨酸能神经元上的NK1R释放谷氨酸。谷氨酸然后激活突触周围的mGlu5Rs，以启动内源性大麻素逆行抑制vlPAG中的GABA能传递，从而导致镇痛。