Inhibitory Effect of Endomorphin-2 Binding to the μ-Opioid Receptor in the Rat Pre-Bötzinger Complex on the Breathing Activity

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• 作者：Jian Qi ; Hui Li ; Ting-Bao Zhao ; Ya-Cheng Lu ; Ting Zhang…
• 关键词：Endomorphin ; 2 ; Neurokinin 1 receptor ; μ ; opioid receptor ; Pre ; Bötzinger complex ; Electron microscopy ; Respiratory depression ; Rat
• 刊名：Molecular Neurobiology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：54
• 期：1
• 页码：461-469
• 全文大小：
• 刊物主题：Neurosciences; Neurobiology; Cell Biology; Neurology;
• 出版者：Springer US
• ISSN：1559-1182
• 卷排序：54

文摘

Opiates are commonly used analgesics that often cause clinical respiratory depression. However, their underlying mechanisms remain unclear. Endomorphin-2 (EM2) is a novel, endogenous tetrapeptide opioid with very high affinity and selectivity for the μ-opioid receptor (MOR). The pre-Bötzinger complex (pre-BötC) is considered the center of respiratory rhythm generation, and the synaptic connections in this region are essential for respiratory rhythm. The present study identified EM2-like immunoreactive (LI) axonal terminals in the pre-BötC of adult rats. Some EM2-LI axonal terminals made principally symmetric synapses with neurokinin 1 receptor (NK1R)-LI or MOR-LI neuronal dendritic processes in the pre-BötC. Unilateral microinjection of EM2 into the pre-BötC decreased breathing frequency and amplitude. A prior microinjection of the selective MOR antagonist β-funaltrexamine (β-FNA) into the pre-BötC prevented the effects of EM2. The present results suggest that EM2-LI axonal terminals modulate NK1R-expressing neurons in the pre-BötC and that EM2 plays a role in respiratory depression through MORs in the pre-BötC.