Brown M C, Levine J L
Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02115, USA.
Neuroscience. 2008 Jun 12;154(1):147-59. doi: 10.1016/j.neuroscience.2007.12.045. Epub 2008 Jan 16.
Stains for acetylcholinesterase (AChE) and retrograde labeling with Fluorogold (FG) were used to study olivocochlear neurons and their dendritic patterns in mice. The two methods gave similar results for location and number of somata. The total number of medial olivocochlear (MOC) neurons in the ventral nucleus of the trapezoid body (VNTB) is about 170 per side. An additional dozen large olivocochlear neurons are located in the dorsal periolivary nucleus (DPO). Dendrites of all of these neurons are long and extend in all directions from the cell bodies, a pattern that contrasts with the sharp frequency tuning of their responses. For VNTB neurons, there were greater numbers of dendrites directed medially than laterally and those directed medially were longer (on average, 25-50% longer). Dendrite extensions were most pronounced for neurons located in the rostral portion of the VNTB. When each dendrite from a single neuron was represented as a vector, and all the vectors summed, the result was also skewed toward the medial direction. DPO neurons, however, had more symmetric dendrites that projected into more dorsal parts of the trapezoid body, suggesting that this small group of olivocochlear neurons has very different physiological properties. Dendrites of both types of neurons were somewhat elongated rostrally, about 20% longer than those directed caudally. These results can be interpreted as extensions of dendrites of olivocochlear neurons toward their synaptic inputs: medially to meet crossing fibers from the cochlear nucleus that are part of the MOC reflex pathway, and rostrally to meet descending inputs from higher centers.
采用乙酰胆碱酯酶（AChE）染色和荧光金（FG）逆行标记法研究小鼠橄榄耳蜗神经元及其树突模式。两种方法在胞体位置和数量上得到了相似的结果。梯形体腹侧核（VNTB）中内侧橄榄耳蜗（MOC）神经元的总数每侧约为170个。另外还有十几个大型橄榄耳蜗神经元位于背侧橄榄旁核（DPO）。所有这些神经元的树突都很长，从细胞体向各个方向延伸，这种模式与其反应的尖锐频率调谐形成对比。对于VNTB神经元，向内侧的树突数量多于向外侧的，且向内侧的树突更长（平均长25 - 50%）。位于VNTB Rostral部分的神经元树突延伸最为明显。当将单个神经元的每个树突表示为一个向量，并将所有向量相加时，结果也偏向内侧方向。然而，DPO神经元的树突更对称，伸向梯形体更靠背侧的部分，这表明这一小群橄榄耳蜗神经元具有非常不同的生理特性。两种类型神经元的树突在 Rostral方向上都有所拉长，比向尾侧的树突长约20%。这些结果可以解释为橄榄耳蜗神经元树突向其突触输入的延伸：向内侧与来自耳蜗核的交叉纤维相遇，这些纤维是MOC反射通路的一部分；向 Rostral与来自更高中枢的下行输入相遇。
