Ingham N J, Thornton S K, McCrossan D, Withington D J
Department of Physiology, The Worsley Medical and Dental Building, University of Leeds, Leeds LS2 9NQ, United Kingdom.
J Neurophysiol. 1998 Dec;80(6):2941-53. doi: 10.1152/jn.1998.80.6.2941.
Neurotransmitter involvement in development and maintenance of the auditory space map in the guinea pig superior colliculus. J. Neurophysiol. 80: 2941-2953, 1998. The mammalian superior colliculus (SC) is a complex area of the midbrain in terms of anatomy, physiology, and neurochemistry. The SC bears representations of the major sensory modalites integrated with a motor output system. It is implicated with saccade generation, in behavioral responses to novel sensory stimuli and receives innervation from diverse regions of the brain using many neurotransmitter classes. Ethylene-vinyl acetate copolymer (Elvax-40W polymer) was used here to deliver chronically neurotransmitter receptor antagonists to the SC of the guinea pig to investigate the potential role played by the major neurotransmitter systems in the collicular representation of auditory space. Slices of polymer containing different drugs were implanted onto the SC of guinea pigs before the development of the SC azimuthal auditory space map, at approximately 20 days after birth (DAB). A further group of animals was exposed to aminophosphonopentanoic acid (AP5) at approximately 250 DAB. Azimuthal spatial tuning properties of deep layer multiunits of anesthetized guinea pigs were examined approximately 20 days after implantation of the Elvax polymer. Broadband noise bursts were presented to the animals under anechoic, free-field conditions. Neuronal responses were used to construct polar plots representative of the auditory spatial multiunit receptive fields (MURFs). Animals exposed to control polymer could develop a map of auditory space in the SC comparable with that seen in unimplanted normal animals. Exposure of the SC of young animals to AP5, 6-cyano-7-nitroquinoxaline-2,3-dione, or atropine, resulted in a reduction in the proportion of spatially tuned responses with an increase in the proportion of broadly tuned responses and a degradation in topographic order. Thus N-methyl--aspartate (NMDA) and non-NMDA glutamate receptors and muscarinic acetylcholine receptors appear to play vital roles in the development of the SC auditory space map. A group of animals exposed to AP5 beginning at approximately 250 DAB produced results very similar to those obtained in the young group exposed to AP5. Thus NMDA glutamate receptors also seem to be involved in the maintenance of the SC representation of auditory space in the adult guinea pig. Exposure of the SC of young guinea pigs to gamma-aminobutyric acid (GABA) receptor blocking agents produced some but not total disruption of the spatial tuning of auditory MURFs. Receptive fields were large compared with controls, but a significant degree of topographical organization was maintained. GABA receptors may play a role in the development of fine tuning and sharpening of auditory spatial responses in the SC but not necessarily in the generation of topographical order of the these responses.
神经递质参与豚鼠上丘听觉空间图谱的发育和维持。《神经生理学杂志》80: 2941 - 2953, 1998年。从解剖学、生理学和神经化学角度来看，哺乳动物的上丘（SC）是中脑的一个复杂区域。上丘承载着与运动输出系统整合的主要感觉模态的表征。它与扫视的产生、对新感觉刺激的行为反应有关，并接受来自大脑不同区域、使用多种神经递质类别的神经支配。在这里使用乙烯 - 醋酸乙烯共聚物（Elvax - 40W聚合物）将慢性神经递质受体拮抗剂递送至豚鼠的上丘，以研究主要神经递质系统在听觉空间的丘系表征中所起的潜在作用。在出生后约20天（DAB），即上丘方位听觉空间图谱发育之前，将含有不同药物的聚合物切片植入豚鼠的上丘。另一组动物在约250 DAB时暴露于氨基膦酰戊酸（AP5）。在植入Elvax聚合物后约20天，检查麻醉豚鼠深层多单元的方位空间调谐特性。在消声、自由场条件下向动物呈现宽带噪声脉冲。神经元反应被用于构建代表听觉空间多单元感受野（MURF）的极坐标图。暴露于对照聚合物的动物能够在上丘中形成与未植入的正常动物所见相当的听觉空间图谱。幼年动物的上丘暴露于AP5、6 - 氰基 - 7 - 硝基喹喔啉 - 2,3 - 二酮或阿托品后，空间调谐反应的比例降低，广谱调谐反应的比例增加，并且地形顺序退化。因此，N - 甲基 - D - 天冬氨酸（NMDA）和非NMDA谷氨酸受体以及毒蕈碱型乙酰胆碱受体似乎在上丘听觉空间图谱的发育中起重要作用。一组从约250 DAB开始暴露于AP5的动物产生的结果与暴露于AP5的幼年组获得的结果非常相似。因此，NMDA谷氨酸受体似乎也参与成年豚鼠上丘听觉空间表征的维持。幼年豚鼠的上丘暴露于γ - 氨基丁酸（GABA）受体阻断剂后，听觉MURF的空间调谐受到了一些但并非完全的破坏。与对照组相比，感受野较大，但仍保持了显著程度的地形组织。GABA受体可能在上丘听觉空间反应的微调与锐化的发育中起作用，但不一定在这些反应的地形顺序的产生中起作用。
