The V0 Interneurons: First-Order Interneurons of the Locomotor CPG?

Abstract

The locomotor Central Pattern Generator (CPG) is a neuronal network capable of producing rhythmic locomotor output independent of sensory or descending input. Attempts to identify component interneurons of the CPG have been aided by the discovery of transcription factors that are expressed by discrete interneuron populations during development. The V0 interneuron population is defined by the expression of the transcription factor Dbx1. Herein I test the hypothesis that V0 interneurons are first-order cells of the locomotor CPG responsible for initiating rhythmic locomotor activity. Anatomical tracing from brainstem sites known to be responsible for the initiation of locomotion reveal that these regions make monosynaptic connections onto V0 cells. Immunohistochemistry demonstrates that V0 cells express 5-HT7 and 5-HT2A receptors, previously shown to be required for locomotor initiation. Taken together these results support the hypothesis that V0 interneurons are first-order interneurons of the locomotor CPG responsible for initiating locomotion.