多巴胺D1受体在豚鼠耳蜗中的作用

Regulation of Dopamine D1 Receptors in Guinea Pig Cochlea

目的观察多巴胺D1受体拮抗剂对豚鼠耳蜗电位及耳声发射的影响,探讨多巴胺D1受体在豚鼠耳蜗中的作用。方法选用健康、耳廓反射灵敏的白色红目豚鼠20只,随机分组,每组10只,以左耳行全耳蜗灌流:(1)灌流人工外淋巴液组;(2)灌流20μmol/L多巴胺D1受体拮抗剂(SCH23390)组。分别在钻孔前、灌流前(0min)、灌流后(5min、15min、30min、60min、120min)通过圆窗记录:(1)短声(click)引出的复合动作电位(CAP)阈值和振幅;(2)4k Hz短音(tone burst)引出的耳蜗微音电位(CM)振幅;(3)畸变产物耳声发射(DPOAE)振幅。绘制CAP及CM振幅输入/输出(I/O)函数曲线。结果灌流人工外淋巴液前后,CAP阈值及振幅的变化均没有统计学意义(P>0.05)。灌流多巴胺D1受体拮抗剂5min后,CAP振幅增高,与灌流前相比具有统计学意义(P=0.005),灌流时间延长,CAP振幅逐渐降低,低于灌流前水平,在刺激声强为110、50、30dB SPL时最明显,差异具有统计学意义(P=0.02),CAP输入/输出函数曲线仍具有非线性特点。灌流人工外淋巴液和多巴胺D1受体拮抗剂前后,CM振幅轻度降低,CM输入/输出函数曲线非线性特点没有明显变化,组间差异没有统计学意义(P>0.05)。灌流人工外淋巴液和多巴胺D1受体拮抗剂对DPOAE振幅没有明显影响,灌流前后DPOAE振幅差异没有统计学意义(P>0.05)。结论多巴胺D1受体拮抗剂可以阻断多巴胺对传入神经的抑制作用,对外毛细胞无影响;这种阻断作用具有瞬时性。

Objective To study the regulation of dopamine D1 receptors in guinea pig cochlea, and changes of co-chlear potentials and otoacoustic emissions after dopamine D1 receptor antagonist perfusion. Methods Twenty healthy guinea pigs were randomly divided to receive left ear whole intracochlear perfusion with either artificial perilymph solu-tions, or with 20 μmol/L dopamine D1 receptor antagonist （SCH23390）. Before and 5, 15, 30, 60 and 120 min after per-fusion, compound action potentials （CAP） evoked by clicks, cochlear microphnics （CM） evoked by 4 kHz tone bursts and distortion product otoacoustic emissions （DPOAE） were recorded and their input/output （I/O） functions obtained. Results There was no significant difference in CAP threshold and amplitude before and after perfusion with the artifi-cial perilymph solution （P＞0.05）. Increased amplitude in CAP was noted 5 min after perfused with SCH23390 （P=0.005）, which decreased as perfusion time prolonged to a level below the pre-perfusion amplitude （P=0.02）. The ampli-tudes of CM and DPOAEs remained unchanged in both groups （P＞0.05）. The input/output function of CAP and CM re-mained nonlinear. Conclusions Dopamine D1 receptor antagonist can block the inhibitory effect of dopamine on the af-ferent nerve without influencing outer hair cells. The effect is temporary.