Crossinhibition

Crossinhibition, sometimes written cross-inhibition, is a phenomenon in which activation of one pathway, response, or cellular state suppresses the activity of a competing pathway, response, or state. It can occur between neural circuits, muscle groups, signaling pathways, or gene regulatory networks. The suppression may be direct, via inhibitory synapses, or indirect, through shared resources, feedback loops, or transcriptional cross-talk.

In the nervous system, crossinhibition is a form of reciprocal inhibition. Activation of a motor pool often triggers inhibitory interneurons that dampen the opposing pool, preventing simultaneous contraction of antagonistic muscles and enabling smooth, coordinated movement. Reciprocal inhibition is a widely observed feature of locomotor circuits and reflex pathways. Crossinhibition also appears in sensory circuits, where the activation of one channel or receptive field reduces the responsiveness of nearby channels, aiding contrast and discrimination.

In cellular signaling and gene regulation, crossinhibition can arise when two pathways compete for limited second messengers, kinases, or transcriptional co-factors. Activation of one pathway may inhibit another by mutual phosphorylation, conformational change, or transcriptional repression. Such cross-talk helps the cell prioritize responses under competing demands and can shape cell fate decisions.

Crossinhibition is related to, but distinct from, lateral inhibition, which emphasizes spatial contrast in sensory arrays. It is a general concept used across neuroscience, physiology, and cell biology to describe how competitive interactions shape behavior and function.