d'Aldin C, Puel J L, Leducq R, Crambes O, Eybalin M, Pujol R
INSERM (U254), Laboratoire de Neurobiologie de l'Audition et Plasticité Synaptique, CHU Hôpital St. Charles, Montpellier, France.
Hear Res. 1995 Oct;90(1-2):202-11. doi: 10.1016/0378-5955(95)00167-5.
This study investigates the role of dopamine, a putative lateral efferent neurotransmitter/modulator, in cochlear physiology and physiopathology. Cochlear potentials were recorded in guinea pigs after intracochlear perfusion of increasing doses (0.1-1 mM) of piribedil, an agonist of the D2/D3 receptors. A dose-dependent reduction in the amplitude of auditory nerve compound action potential (CAP) was observed, predominantly at high-intensity tone-burst stimulations, and without significant effect on CAP threshold. There was no variation of cochlear microphonic and summating potential. When 1 mM piribedil was perfused into the cochlea during continuous 130 dB SPL pure tone exposure (6 kHz, 15 min), CAP threshold shifts were significantly less than in control animals with artificial perilymph-perfused cochleas. No dendritic damage was observed, although there was evident hair cell damage. Similarly, radial dendrites were clearly protected against ischemia-induced damage when 1 mM piribedil was applied prior to a 10-min ischemia. These results suggest that dopamine modulates the activity of radial afferent fibers via D2/D3 receptors. The protective effect of piribedil during acoustic trauma or ischemia suggests that this modulation corresponds to a prevention of excitotoxicity due to dysfunction of inner hair cell neurotransmission.
本研究探讨了多巴胺（一种假定的外侧传出神经递质/调节剂）在耳蜗生理和病理生理中的作用。在豚鼠耳蜗内灌注递增剂量（0.1 - 1 mM）的匹莫齐特（一种D2/D3受体激动剂）后，记录耳蜗电位。观察到听神经复合动作电位（CAP）幅度呈剂量依赖性降低，主要发生在高强度短纯音刺激时，且对CAP阈值无显著影响。耳蜗微音器电位和总和电位无变化。当在持续130 dB SPL纯音暴露（6 kHz，15分钟）期间向耳蜗灌注1 mM匹莫齐特时，CAP阈值变化明显小于人工外淋巴灌注耳蜗的对照动物。尽管存在明显的毛细胞损伤，但未观察到树突损伤。同样，在10分钟缺血前应用1 mM匹莫齐特时，放射状树突明显受到保护，免受缺血诱导的损伤。这些结果表明，多巴胺通过D2/D3受体调节放射状传入纤维的活性。匹莫齐特在声损伤或缺血期间的保护作用表明，这种调节对应于预防由于内毛细胞神经传递功能障碍引起的兴奋性毒性。
