Tanabe Ayaka, Fujii Tomoko, Onimaru Hiroshi
Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Neurosci Lett. 2005 Feb 25;375(1):19-22. doi: 10.1016/j.neulet.2004.10.058. Epub 2004 Nov 30.
We investigated the effect of a mu-opioid agonist, DAGO, on the respiratory frequency of pons-medulla-spinal cord preparations from newborn rats. Bath application of a low concentration of DAGO (0.2 microM) facilitated respiratory rhythm in pons-medulla-spinal cord preparations, whereas it induced respiratory depression in medulla-spinal cord preparations (without pons). At a higher concentration (1.0 microM), at which the inspiratory burst generation in the medulla was strongly depressed, the respiratory rhythm in half of the pons-medulla-spinal cord preparations increased and then decreased, thus showing a biphasic response. In the other half of these preparations, only the facilitatory effect was observed. The burst rate of pre-inspiratory neurons in the rostral ventrolateral medulla was also facilitated by DAGO application. Such facilitation of the respiratory rhythm is probably due to disinhibition of a pontine inhibitory system. Our findings also suggest the existence of a pontine excitatory system, which is depressed by the pontine inhibitory system under control conditions.
我们研究了μ阿片受体激动剂DAGO对新生大鼠脑桥-延髓-脊髓标本呼吸频率的影响。浴槽给药低浓度的DAGO（0.2微摩尔）可促进脑桥-延髓-脊髓标本的呼吸节律，而在延髓-脊髓标本（无脑桥）中则诱导呼吸抑制。在较高浓度（1.0微摩尔）时，延髓吸气爆发的产生受到强烈抑制，一半的脑桥-延髓-脊髓标本的呼吸节律先增加后降低，呈现双相反应。在另一半这些标本中，仅观察到促进作用。应用DAGO也可促进延髓头端腹外侧前吸气神经元的爆发频率。这种呼吸节律的促进作用可能是由于脑桥抑制系统的去抑制作用。我们的研究结果还提示存在一个脑桥兴奋系统，在对照条件下该系统受到脑桥抑制系统的抑制。
