McEchron M D, Green E J, Winters R W, Nolen T G, Schneiderman N, McCabe P M
Department of Psychology, University of Miami, Coral Gables, Florida 33124, USA.
J Neurosci. 1996 Feb 1;16(3):1273-83. doi: 10.1523/JNEUROSCI.16-03-01273.1996.
In this study we examined inputs to neurons in the medial subnucleus of the medial geniculate nucleus (mMG) for changes of synaptic efficacy associated with heart-rate conditioning to an auditory conditioned stimulus (CS). Conditioning-related changes of synaptic efficacy were measured in awake animals by examining mMG single-unit responses evoked by stimulation of one of two areas that send auditory CS and nonauditory information monosynaptically to the mMG, the brachium of the inferior colliculus (BlC) and the superior colliculus (SC). Synaptic efficacy was measured before, immediately after, and 1 hr after one session of classical conditioning with a tone CS and a corneal airpuff unconditioned stimulus. To determine whether conditioning produced changes of synaptic efficacy on the auditory BlC inputs to mMG cells and not general changes of cellular excitability, analyses of synaptic efficacy were performed on the mMG units that exhibited short-latency evoked responses (< 3.5 msec) to both BlC and SC stimulation. Analyses revealed that the BlC but not the SC test stimulus-evoked unit activity from the same neurons exhibited the following changes immediately after conditioning: decreases in unit response latency, increases in unit response reliability, and increases in spike frequency. BlC-evoked unit responses after pseudoconditioning did not exhibit these changes in unit responding. These results suggest that the synapses carrying auditory CS information to mMG neurons increase in strength as the result of associative conditioning with an acoustic CS. Some of these changes of synaptic efficacy remained 1 hr after training.
在本研究中，我们检查了内侧膝状核内侧亚核（mMG）中神经元的输入，以寻找与对听觉条件刺激（CS）进行心率条件反射相关的突触效能变化。通过检查由两个区域之一的刺激诱发的mMG单单位反应来测量清醒动物中与条件反射相关的突触效能变化，这两个区域将听觉CS和非听觉信息单突触地发送到mMG，即下丘臂（BlC）和上丘（SC）。在使用音调CS和角膜吹气非条件刺激进行一次经典条件反射之前、之后立即以及1小时后测量突触效能。为了确定条件反射是否在mMG细胞的听觉BlC输入上产生了突触效能变化，而不是细胞兴奋性的一般变化，对那些对BlC和SC刺激均表现出短潜伏期诱发反应（<3.5毫秒）的mMG单位进行了突触效能分析。分析显示，在条件反射后立即，来自相同神经元的BlC而非SC测试刺激诱发的单位活动表现出以下变化：单位反应潜伏期缩短、单位反应可靠性增加以及放电频率增加。假条件反射后BlC诱发的单位反应在单位反应方面未表现出这些变化。这些结果表明，将听觉CS信息传递给mMG神经元的突触由于与声学CS的联合条件反射而增强。其中一些突触效能变化在训练后1小时仍然存在。
