5-HT_(1A)受体对新生大鼠离体延髓脑片呼吸节律性放电的调制

5-HT_(1A) receptors are involved in the modulation of respiratory rhythmical discharge activity in the medulla oblongata slice preparation of neonatal rats

本研究探讨5-HT1A受体在延髓基本节律性呼吸放电发生和调节中的作用。以改良Kreb’s液恒温灌流新生Sprague-Dawley大鼠离体延髓脑片标本,稳定记录与之相连的舌下神经根的呼吸节律性放电活动(respiratory rhythmical discharge activity,RRDA)后,第一组在灌流液中分别单独给予5-HT1A受体的特异性激动剂8-羟四氢萘[(+/-)-8-hydroxy-2-(di-N-propylamino)tetralin hydrobromide,8-OHDPAT]和特异性拮抗剂多次甲基多苯基多异氰酸酯[4-iodo-N-[2-[4-methoxyphenyl]-1-piperazinyl]ethyl]-N-2-pyridynyl-benzamide hydrochloride,PMPPI];第二组分别先后给予8-OHDPAT和8-OHDPAT+PMPPI,观察舌下神经根RRDA的变化,探讨5-HT1A受体对其调节作用。结果显示,给予8-OHDPAT后,呼吸周期(respiratory cycle,RC)和呼气时程(expiratory time,TE)显著延长,放电的积分幅度(integral amplitude,IA)持续降低,吸气时程(inspiratory time,TI)无明显变化;给予PMPPI后RC、TI和TE明显缩短,舌下神经根IA无明显变化,且8-OHDPAT的作用可部分被PMPPI逆转。结果提示,5-HT1A受体参与了哺乳动物基本呼吸节律的产生和调节。

The present study was carried out to determine the role of 5-HT1A receptors in the generation and modulation of basic respiratory rhythm. Neonatal （aged 0-3 d） Sprague-Dawley rats of either sex were used. The medulla oblongata slice was prepared and the surgical procedure was performed in the modified Kreb＇s solution （MKS） with continuous carbogen （95% O2 and 5% CO2）, and ended in 3 min. In cold MKS, a 600-700 μm single transverse slice was cut, which was rostral to the edge of area postrema and retained the hypoglossal nerve roots and some parts of the ventral respiratory group. The preparation was quickly transferred to a recording chamber and continuously perfused with carbogen-saturated MKS at a rate of 4-6 mL/min at 27-29 ℃. Glass adsorb-electrodes containing Ag-AgCl needle were attached to the ventral roots of the hypoglossal nerve. Respiratory rhythmical discharge activity （RRDA） of the rootlets of hypoglossal nerve was recorded. Ten medulla oblongata slice preparations were divided into two groups. In group I, 5-HT1A receptor specific agonist （＋/-）-8-hydroxy-2-（di-N-propylamino）tetralin hydrobromide （8-OHDPAT, 20 μmol/L） was added into the perfusion solution for 10 rain first, after washing out, the 5-HT1A antagonist [4-iodo-N-[2-[4-methoxyphenyl]-1-piperazinyl]ethyl]-N-2-pyridynyl- benzamide hydrochloride] （PMPPI, 10 μmol/L） was applied to the perfusion solution for 10 min. In group II, after application of 8-OHDPAT for 10 min, additional PMPPI was added into the perfusion solution for 10 min. The discharges of the rootlets of hypoglossal nerve were recorded. Signals were amplified and band-pass filtered （100-3.3 kHz）. Data were sampled （1-10 kHz） and stored in the computer via BL-420 biological signal processing system. Our results showed that 8-OHDPAT increased the respiratory cycle （RC） and expiratory time （TE） as well as reduced the integral amplitude （IA）, but the changes of the inspiratory time （TI） were not statistically significant. PMPPI induced a significant decrease in RC, TE and TI, but the changes of IA were not statisticallysignificant. The effect of 8-OHDPAT on the respiratory rhythm was partially reversed by additional application of PMPPI. Taken together with previous results, 5-HT1A receptors may play an important role in the modulation of RRDA in the medulla oblongata slice preparation of neonatal rats.