Zhu Mingyan, Cho Young K, Li Cheng-Shu
Department of Anatomy, Southern Illinois University School of Medicine, Life Science III Room 2073, 1135 Lincoln Dr., Carbondale, IL 62901, USA.
J Neurophysiol. 2009 Jan;101(1):258-68. doi: 10.1152/jn.90648.2008. Epub 2008 Nov 19.
The rostral nucleus of the solitary tract (NST) is the first central relay in the gustatory pathway and plays a key role in processing and modulation of gustatory information. Here, we investigated the effects of opioid receptor agonists and antagonists on synaptic responses of the gustatory parabrachial nuclei (PbN)-projecting neurons in the rostral NST to electrical stimulation of the solitary tract (ST) using whole cell recordings in the hamster brain stem slices. ST-evoked excitatory postsynaptic currents (EPSCs) were significantly reduced by met-enkephalin (MetE) in a concentration-dependent fashion and this effect was eliminated by naltrexone hydrochloride, a nonselective opioid receptor antagonist. Bath application of naltrindole hydrochloride, a selective delta-opioid receptor antagonist, eliminated MetE-induced reduction of EPSCs, whereas CTOP, a selective mu-opioid receptor antagonist had no effect, indicating that delta-opioid receptors are involved in the reduction of ST-evoked EPSCs induced by MetE. SNC80, a selective delta-opioid receptor agonist, mimicked the effect of MetE. The SNC80-induced reduction of ST-evoked EPSCs was eliminated by 7-benzylidenenaltrexone, a selective delta1-opioid receptor antagonist but not by naltriben mesylate, a selective delta2-opioid receptor antagonist, indicating that delta1-opioid receptors mediate the reduction of ST-evoked EPSCs induced by SNC80. Single-cell reverse transcriptase-polymerase chain reaction analysis revealed the presence of delta1-opioid receptor mRNA in cells that responded to SNC80 with a reduction in ST-evoked EPSCs. Moreover, Western blot analysis demonstrated the presence of 40-kDa delta-opioid receptor proteins in the rostral NST tissue. These results suggest that postsynaptic delta1-opioid receptors are involved in opioid-induced reduction of ST-evoked EPSCs of PbN-projecting rostral NST cells.
孤束核吻侧亚核（NST）是味觉通路中的首个中枢中继站，在味觉信息的处理和调制中起关键作用。在此，我们使用仓鼠脑干切片的全细胞记录，研究了阿片受体激动剂和拮抗剂对吻侧NST中投射至味觉臂旁核（PbN）的神经元对孤束（ST）电刺激的突触反应的影响。甲硫氨酸脑啡肽（MetE）以浓度依赖性方式显著降低了ST诱发的兴奋性突触后电流（EPSCs），且这种效应被非选择性阿片受体拮抗剂盐酸纳曲酮消除。浴用选择性δ阿片受体拮抗剂盐酸纳曲吲哚消除了MetE诱导的EPSCs降低，而选择性μ阿片受体拮抗剂CTOP则无此作用，表明δ阿片受体参与了MetE诱导的ST诱发EPSCs的降低。选择性δ阿片受体激动剂SNC80模拟了MetE的作用。SNC80诱导的ST诱发EPSCs降低被选择性δ1阿片受体拮抗剂7-苄叉基纳曲酮消除，但未被选择性δ₂阿片受体拮抗剂甲磺酸纳曲苄消除，表明δ1阿片受体介导了SNC80诱导的ST诱发EPSCs的降低。单细胞逆转录聚合酶链反应分析显示，在对SNC80有反应且ST诱发EPSCs降低的细胞中存在δ1阿片受体mRNA。此外，蛋白质印迹分析表明吻侧NST组织中存在40 kDa的δ阿片受体蛋白。这些结果表明，突触后δ1阿片受体参与了阿片类药物诱导的投射至PbN的吻侧NST细胞的ST诱发EPSCs的降低。
