Bell C C, Grant K
Robert S. Dow Neurological Sciences Institute, Good Samaritan Hospital, Portland, Oregon 97210.
J Neurosci. 1989 Mar;9(3):1029-44. doi: 10.1523/JNEUROSCI.09-03-01029.1989.
Knollenorgan electroreceptors in mormyrid fish are concerned with electrocommunication, i.e., with detecting electric organ discharges (EODs) of other electric fish. But knollenorgan electroreceptors are also activated by the fish's own EOD. Potential interference by such self-stimulation is blocked by an inhibitory corollary discharge in the nucleus of the electrosensory lateral line lobe (NELL), the first central relay of the knollenorgan pathway. This study used intracellular recording and staining to examine the mechanism of the corollary inhibition and the specializations in anatomy and physiology that permit the accurate relaying of temporal information about the EODs of other fish. Several events are recorded inside primary knollenorgan afferents in addition to a large orthodromic action potential. The additional events include small orthodromic electronic epsps, postsynaptic action potentials, and a corollary discharge inhibitory postsynaptic potential (ipsp) associated with the EOD motor command. These additional events are also recorded in NELL cells and almost certainly originate there. Electrical coupling between afferents and cells makes it possible to observe the events inside primary afferents. The corollary discharge ipsp in the cell is associated with a conductance increase and inverts rapidly when recorded with chloride-containing electrodes, supporting a hypothesis of GABA mediation. The ipsp lasts longer in cells than in afferents. Each electrotonic excitatory postsynaptic potential (epsp) is probably caused by a single primary afferent, and any one of several epsps in a given cell seems capable of eliciting a postsynaptic spike in that cell. The epsps follow stimulation rates as high as 500/sec with minimal variability. No lateral inhibition is observed in NELL. These and other properties indicate that the knollenorgan pathway is specialized for temporal information rather than spatial or intensity information.
长颌鱼的球状体电感受器与电通讯有关，即用于探测其他发电鱼的放电（EOD）。但球状体电感受器也会被鱼自身的EOD激活。电感受侧线叶核（NELL）中的抑制性伴随放电会阻断这种自我刺激可能产生的干扰，NELL是球状体通路的第一个中枢中继站。本研究采用细胞内记录和染色技术，研究伴随抑制的机制以及在解剖学和生理学上的特化，这些特化使得关于其他鱼类EOD的时间信息能够准确中继。除了一个大的顺向动作电位外，在初级球状体传入纤维内还记录到了几个事件。这些额外的事件包括小的顺向电兴奋性突触后电位（epsp）、突触后动作电位以及与EOD运动指令相关的伴随放电抑制性突触后电位（ipsp）。这些额外的事件在NELL细胞中也有记录，几乎可以肯定是起源于那里。传入纤维与细胞之间的电耦合使得观察初级传入纤维内部的事件成为可能。细胞中的伴随放电ipsp与电导增加有关，当用含氯电极记录时会迅速反转，这支持了γ-氨基丁酸（GABA）介导的假说。ipsp在细胞中的持续时间比在传入纤维中更长。每个电紧张性兴奋性突触后电位（epsp）可能由单个初级传入纤维引起，给定细胞中的几个epsp中的任何一个似乎都能够在该细胞中引发突触后峰电位。epsp能够跟随高达500次/秒的刺激频率，且变化极小。在NELL中未观察到侧向抑制。这些以及其他特性表明，球状体通路专门用于传递时间信息，而非空间或强度信息。
