Wu S H, Kelly J B
Psychology Department, Carleton University, Ottawa, Ontario, Canada.
J Neurosci. 1992 Aug;12(8):3084-97. doi: 10.1523/JNEUROSCI.12-08-03084.1992.
The synaptic pharmacology of the lateral superior olive (LSO) and medial nucleus of the trapezoid body (MNTB) was examined in a brain slice preparation of the mouse superior olivary complex (SOC). Physiological responses in SOC were elicited by electrical stimulation of the trapezoid body ipsilateral or contralateral to the recording site, and bilateral interactions were investigated by combined ipsilateral and contralateral stimulation. Pharmacological effects were tested by bath application of amino acid agonists and antagonists. Neurons in MNTB were excited by contralateral stimulation and unaffected by ipsilateral stimulation. Excitatory amino acid (EAA) agonists--kainic acid (KA), quisqualic acid (QA), or L-glutamate--caused spontaneous firing at low concentrations and eliminated responses at higher concentrations in MNTB. The EAA agonist NMDA had relatively little effect at comparable concentrations. Stimulus-elicited responses were blocked by non-NMDA antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitro-quinoxaline-2,3-dione (DNQX) and by the nonspecific EAA antagonist kynurenic acid, but were unaffected by the NMDA antagonist D,L-2-amino-5-phosphonovaleric acid (APV). LSO neurons were typically excited by ipsilateral stimulation and inhibited by contralateral stimulation. In LSO, KA, QA, and L-glutamate caused spontaneous firing at low concentrations and eliminated responses at higher concentrations, and NMDA had relatively little effect. Excitatory responses in the vast majority of LSO neurons were blocked by CNQX, DNQX, or kynurenic acid. Some responses were also blocked by APV. LSO neurons were affected by glycine, and contralateral inhibition in LSO was completely blocked by strychnine. NMDA also blocked inhibition in LSO. These results indicate that excitation of both MNTB and LSO neurons is mediated primarily by an EAA neurotransmitter through non-NMDA receptors and that contralateral inhibition of LSO cells is mediated through strychnine-dependent glycine receptors. NMDA receptors may play a role in binaural processing by modulating contralateral inhibitory input to LSO.
在小鼠上橄榄复合体（SOC）的脑片标本中，研究了外侧上橄榄核（LSO）和斜方体内侧核（MNTB）的突触药理学。通过电刺激记录位点同侧或对侧的斜方体来引发SOC中的生理反应，并通过同侧和对侧联合刺激来研究双侧相互作用。通过在浴槽中应用氨基酸激动剂和拮抗剂来测试药理学效应。MNTB中的神经元受到对侧刺激的兴奋，而不受同侧刺激的影响。兴奋性氨基酸（EAA）激动剂—— kainic酸（KA）、quisqualic酸（QA）或L-谷氨酸——在低浓度时引起自发放电，而在高浓度时消除MNTB中的反应。EAA激动剂NMDA在可比浓度下作用相对较小。刺激引发的反应被非NMDA拮抗剂6-氰基-7-硝基喹喔啉-2,3-二酮（CNQX）和6,7-二硝基喹喔啉-2,3-二酮（DNQX）以及非特异性EAA拮抗剂犬尿喹啉酸阻断，但不受NMDA拮抗剂D，L-2-氨基-5-磷酸戊酸（APV）的影响。LSO神经元通常受到同侧刺激的兴奋，并受到对侧刺激的抑制。在LSO中，KA、QA和L-谷氨酸在低浓度时引起自发放电，在高浓度时消除反应，而NMDA作用相对较小。绝大多数LSO神经元中的兴奋性反应被CNQX、DNQX或犬尿喹啉酸阻断。一些反应也被APV阻断。LSO神经元受甘氨酸影响，LSO中的对侧抑制被士的宁完全阻断。NMDA也阻断LSO中的抑制。这些结果表明，MNTB和LSO神经元的兴奋主要由EAA神经递质通过非NMDA受体介导介导，并且LSO细胞的对侧抑制是通过士的宁依赖性甘氨酸受体介导的。NMDA受体可能通过调节对LSO的对侧抑制性输入在双耳处理中发挥作用。
