Brainstem premotor circuits transform dental sensory input into coordinated jaw opening

Protective actions require the rapid transformation of damage into coordinated activity of motor pools, yet the brainstem circuits implementing this operation remain poorly defined. Here, we use the tooth-trigeminal system to identify molecularly specified pathways linking intradental sensory input to opposing jaw motor pools. Optogenetic activation of tooth-associated sensory afferents evoked rapid, stimulus-locked jaw-opening. Intradental afferents formed functional monosynaptic connections with Pdyn+ neurons in the 5Sol transition zone and Calb2+ neurons in the 5Tr transition zone, identifying these regions as sensory-recipient premotor interfaces. Predominantly excitatory Pdyn+ 5Sol neurons provided monosynaptic input to anterior digastric motor neurons, whereas predominantly inhibitory Calb2+ 5Tr neurons provided bilateral monosynaptic input to masseter motor neurons. Activation of Pdyn+ 5Sol neurons was sufficient to evoke jaw opening. Together, these findings define complementary brainstem pathways positioned to couple jaw-opening drive with inhibition of antagonistic jaw-closing output, revealing a withdrawal-like sensorimotor computation adapted to cranial biomechanics.