Structural correlates of recurrent collateral interneurons producing both electrical and chemical inhibitions of the...

Intracellular injections of horseradish peroxidase provided a basis for morphological identification of inhibitory interneurons belonging to the recurrent collateral network of the Mauthner cell. Their axons dilate to form unusually large bulbs surrounding the axon cap. The morphological appearance of these bulbs as well as intracellular recordings at their level indicate that they behave as nodes and serve as a final source of current for electrical inhibition of the Mauthner cell. The axon of each interneuron gives rise to two different groups of fibres which are respectively fitted for the mediation of electrical and chemical inhibitions of their target cell.