Tunstall Mark J, Oorschot Dorothy E, Kean Annabel, Wickens Jeffery R
Department of Anatomy and Structural Biology and the Neuroscience Research Centre, School of Medical Sciences, University of Otago, Dunedin, New Zealand.
J Neurophysiol. 2002 Sep;88(3):1263-9. doi: 10.1152/jn.2002.88.3.1263.
The spiny projection neurons are by far the most numerous type of striatal neuron. In addition to being the principal projection neurons of the striatum, the spiny projection neurons also have an extensive network of local axon collaterals by which they make synaptic connections with other striatal projection neurons. However, up to now there has been no direct physiological evidence for functional inhibitory interactions between spiny projection neurons. Here we present new evidence that striatal projection neurons are interconnected by functional inhibitory synapses. To examine the physiological properties of unitary inhibitory postsynaptic potentials (IPSPs), dual intracellular recordings were made from pairs of spiny projection neurons in brain slices of adult rat striatum. Synaptic interactions were found in 9 of 45 pairs of neurons using averages of 200 traces that were triggered by a single presynaptic action potential. In all cases, synaptic interactions were unidirectional, and no bidirectional interactions were detected. Unitary IPSPs evoked by a single presynaptic action potential had a peak amplitude ranging from 157 to 319 microV in different connections (mean: 277 +/- 46 microV, n = 9). The percentage of failures of single action potentials to evoke a unitary IPSP was estimated and ranged from 9 to 63% (mean: 38 +/- 14%, n = 9). Unitary IPSPs were reversibly blocked by bicuculline (n = 4) and had a reversal potential of -62.4 +/- 0.7 mV (n = 5), consistent with GABA-mediated inhibition. The findings of the present study correlate very well with anatomical evidence for local synaptic connectivity between spiny projection neurons and suggest that lateral inhibition plays a significant role in the information processing operations of the striatum.
棘状投射神经元是迄今为止纹状体中数量最多的神经元类型。除了作为纹状体的主要投射神经元外，棘状投射神经元还具有广泛的局部轴突侧支网络，通过这些网络它们与其他纹状体投射神经元形成突触连接。然而，到目前为止，尚无直接的生理学证据表明棘状投射神经元之间存在功能性抑制性相互作用。在此，我们提供了新的证据，表明纹状体投射神经元通过功能性抑制性突触相互连接。为了研究单突触抑制性突触后电位（IPSPs）的生理学特性，在成年大鼠纹状体脑片上对成对的棘状投射神经元进行了双细胞内记录。在45对神经元中的9对中发现了突触相互作用，使用由单个突触前动作电位触发的200条轨迹的平均值。在所有情况下，突触相互作用都是单向的，未检测到双向相互作用。单个突触前动作电位诱发的单突触IPSPs在不同连接中的峰值幅度范围为157至319微伏（平均值：277±46微伏，n = 9）。估计单个动作电位未能诱发单突触IPSPs的失败百分比范围为9%至63%（平均值：38±14%，n = 9）。单突触IPSPs被荷包牡丹碱可逆性阻断（n = 4），其反转电位为-62.4±0.7毫伏（n = 5），与GABA介导的抑制作用一致。本研究的结果与棘状投射神经元之间局部突触连接的解剖学证据非常吻合，并表明侧向抑制在纹状体的信息处理操作中起重要作用。
