von Bartheld C S
Hearing Development Laboratory, University of Washington School of Medicine, Seattle.
Brain Behav Evol. 1994;44(2):61-73. doi: 10.1159/000113570.
The paratympanic organ (PTO) is a small sense organ in the middle ear of birds. This luminal organ contains mechanoreceptors (hair cells) with afferent and efferent innervation and may function as a baroreceptor. The hypothesis that elastic ligaments of the middle ear may be involved in the transduction of barometric pressure was tested. Two elastic ligaments are shown to attach to the PTO. The columellar-squamosal ('Platner's') ligament inserts at its caudal pole; the superior portion of the superior drum-tubal ligament attaches at the rostral tip of the organ. To determine if pressure to the tympanic membrane and tension of ligaments may cause lumen changes in the PTO, the length of elastic ligaments, and the length, volume and configuration of the PTO were measured in normal animals and in animals following application of positive or negative pressure to the tympanic membrane. The rostral pole of the PTO changes its shape differentially as a function of the tension of the superior drum-tubal ligament, resulting in volume shifts of about 10% of the total volume in the PTO. With negative pressure, volume moves from the rostral pole to the caudal half of the PTO; with positive pressure, volume shifts rostrally. Displacement of fluid in the lumen of the PTO thus may stimulate the paratympanic hair cells. Tracing of efferent projections to the PTO with the fluorescent compound DiI reveals a cluster of about 40 labeled neurons at the caudal pole of the ventral facial motor nucleus adjacent to the superior olive. These findings support the notion that the PTO may be part of a neural circuit that controls the position of the tympanic membrane and may mediate barometric perception in birds.
鼓室旁器官（PTO）是鸟类中耳中的一个小感觉器官。这个腔内器官含有具有传入和传出神经支配的机械感受器（毛细胞），可能起到压力感受器的作用。我们测试了中耳的弹性韧带可能参与气压传导的假说。研究显示有两条弹性韧带附着于PTO。镫骨-鳞骨（“普拉特纳氏”）韧带在其尾极处插入；上鼓室-咽鼓管韧带的上部附着于该器官的吻端。为了确定鼓膜所受压力和韧带张力是否会导致PTO的管腔变化，我们在正常动物以及对鼓膜施加正压或负压后的动物中测量了弹性韧带的长度、PTO的长度、体积和形态。PTO的吻极会根据上鼓室-咽鼓管韧带的张力不同而改变其形状，导致PTO总体积发生约10%的体积变化。施加负压时，体积从PTO的吻极移向尾半部分；施加正压时，体积则向吻侧移位。因此，PTO管腔内液体的移位可能会刺激鼓室旁毛细胞。用荧光化合物DiI追踪至PTO的传出投射，发现在腹侧面神经运动核尾极靠近上橄榄核处有一群约40个标记神经元。这些发现支持了以下观点：PTO可能是控制鼓膜位置的神经回路的一部分，并且可能介导鸟类的气压感知。
