A VTA-pontine GABA pathway biases locomotor direction via local and distal inhibition

Abstract

Locomotor direction in mammals is implemented by descending circuits, yet how midbrain selection systems bias directional motor output remains unclear. Here we define a projection-defined inhibitory pathway from the ventral tegmental area to the oral pontine reticular nucleus (VTAPnO) whose activation is sufficient to drive backward locomotion. These TH- VTA neurons form monosynaptic GABAA synapses locally while projecting to PnO, establishing a dual local-projection inhibitory architecture. Somatic activation reliably induced backward locomotion, and selective stimulation of VTAPnO terminals reproduced the effect. Pathway recruitment produced a rapid transient increase in dopaminergic single-unit activity and frequency-dependent increases in dopaminergic population calcium signals in awake mice. During forced locomotion, chronically recorded VTAPnO neurons were preferentially engaged during reverse compared to forward rotations. Together, these findings reveal a projection-defined midbrain pathway that biases locomotor direction through coordinated local inhibition and distal engagement of a brainstem premotor node.