King A S, King D Z, Hodges R D, Henry J
Cell Tissue Res. 1975 Oct 27;162(4):459-73. doi: 10.1007/BF00209346.
Efferent and reciprocal synapses have been demonstrated in the carotid body of the domestic fowl (Gallus gallus domesticus). Synapses were also found with purely afferent morphology, but were probably components of reciprocal synapses. The general morphology of the endings suggested the presence of two types of axon, afferent axons making reciprocal and perhaps afferent synapses with Type I cells, and efferent axons making efferent synapses with Type I cells. A few axo-dendritic synapses were also found. The dense-cored vesicles associated with the afferent components of reciprocal synapses and with the possible true afferent synapses varied in diameter and core but could belong to one population of pre-synaptic vesicles. These observations are consistent wtih a new theory for the carotid body receptor mechanism. This proposes a spontaneously discharging afferent axon inhibited by an inhibitory transmitter substance released by the Type I cell via the "afferent" component of its reciprocal synapse, the "efferent" component inhibiting this release. Besides this chemoreceptor modulation of its afferent axon, the Type I cell may also have a general secretory function.
在家禽（家鸡）的颈动脉体中已证实存在传出性和交互性突触。也发现了具有纯传入形态的突触，但它们可能是交互性突触的组成部分。末梢的一般形态表明存在两种类型的轴突，传入轴突与I型细胞形成交互性突触，可能还有传入性突触，传出轴突与I型细胞形成传出性突触。还发现了一些轴突-树突突触。与交互性突触的传入成分以及可能真正的传入性突触相关的有致密核心小泡，其直径和核心各不相同，但可能属于一个突触前小泡群体。这些观察结果与颈动脉体受体机制的新理论一致。该理论提出，一个自发放电的传入轴突受到I型细胞通过其交互性突触的“传入”成分释放的抑制性递质物质的抑制，“传出”成分抑制这种释放。除了对其传入轴突的这种化学感受器调节外，I型细胞可能还具有一般的分泌功能。
