8-OH-DPAT对新生鼠离体延髓脑片呼吸节律性放电的影响

Effects of 8-OH-DPAT on respiratory rhythmical discharge activity in isolated neonatal rat brainstem slice

目的探讨激活5-HT1A受体对延髓基本节律性呼吸放电的影响。方法制备20只新生SD大鼠(0～3d)离体延髓脑片标本,以改良的Kreb's液恒温灌流,稳定记录到与之相连的舌下神经的呼吸节律性放电活动(RRDA)后,随机分成Ⅰ～Ⅳ组(每组n=5)。Ⅰ～Ⅳ组给予5-HT1A受体的特异性激动剂(+/-)-8-hydroxy-2-(di-N-propylamino)tetralin hydrobromide(8-OH-DPAT),浓度分别为1、5、10、20μmol/L持续灌流10min,观察给药后1、3、5min时舌下神经的呼吸节律性放电活动的变化。结果给药前后不同时间点之间呼吸周期(RC)有显著性差异(F=181.219,P<0.001),各浓度在给药前RC最小,给药后逐渐延长,5min时达到最大。各浓度之间有显著性差异(P<0.001),给药后各时间点1μmol/L的RC最小,给药浓度增大,RC延长,20μmol/L时RC最大。给药前后和不同浓度之间存在交互效应(P<0.001)。给药前后不同时间点之间积分幅度(IA)有显著性差异(P<0.001),在10μmol/L和20μmol/L浓度组中给药前后不同时间点之间有显著性差异(P=0.017和0.001)。各浓度之间有显著性差异(P<0.001),给药后各时间点1μmol/L的IA最大,给药浓度增大IA减小,20μmol/L的IA最小。给药前后和不同浓度之间存在交互效应(P=0.002)。结论(1)8-OH-DPAT长效抑制吸气活动,对新生大鼠离体延髓脑片标本呼吸周期具有剂量依赖性延长作用,对频率和积分幅度具有剂量依赖性抑制作用。(2)5-HT1A受体参与了哺乳动物基本呼吸节律的产生和调节。

Objective To investigate the role of 5-HT1A receptors in the generation and modulation of basic respiration rhythm. Methods Brainstem slices of 20 newborn SD rats （0-3 days） were prepared and respiratory rhythmical discharge activity （RRDA） of the hypoglossal nerve was recorded by suction electrode on these preparations including the medial region of the nucleus retrofacialis （mNRF） with the hypoglossal nerve rootlets retained, and the effects of 5-HT1A receptors on RRDA were investigated by application of specific agonist of 5-HT1A receptors 8-OH-DPAT in the perfusion solution. The 20 neonatal rats were divided into 4 groups and the brainstem slices were perfused continuously for 10 min with different concentrations of S-OH-DPAT （1, 5, 10, 20 μmol/L, respectively）. RRDA was recorded before and 1, 3, 5 min after 8-OH-DPAT perfusion. Results The respiratory cycles （RC） varied significantly between the different time points of 8-OH-DPAT administration （F=181.219, P〈0.001）, which was the shortest before 8-OH-DPAT administration and increased progressively after administration till reaching the maximum 5 min after the administration. The RC also varied significantly between different 8-OH-DPAT concentrations （F=61.675, P〈0.001）. At each time point after 8-OH-DPAT administration, RC was the shortest with 1 μmol/L and maximum with 20 μmol/L 8-OH-DPAT. A crossover effect was observed between the time and administered 8-OH-DPAT concentration （F=22.940, P〈0.001）. The integrated amplitude （IA） was significantly different between different time points of 8-OH-DPAT administration （F=20.949, P〈0.001）, and the application of 10 and 20 μmol/L 8-OH-DPAT resulted in significant IA decrement （F=5.050, P=0.017; F=51.389, P=0.001, respectively）. Different concentrations of 8-OH-DPAT also significantly affected IA （F=41.027, P〈0.001）, and at each time point after administration, IA was the maximum with 1 μmol/L and minimum with 20 μmol/L 8-OH-DPAT, also showing a crossover effect between time and 8-OH-DPAT concentration （F=3.483, P=0.002）. Conclusions 8-OH-DPAT induces a dose-dependent increase in RC and a dose-dependent inhibition of the IA and burst frequency, with long-lasting inhibitory effect on the inspiration. 5-HT1A receptors play an important role in the modulation of the RRDA in isolated neonatal rat brainstem slice.