Vagal pathways to spinothalamic tract cells in upper spinal cord. Vagal pathways are shown (green) with a relay through the nucleus of the solitary tract (NTS), but see Fig. 4 for other possibilities. Vagal input probably reaches the T₁-T₅ segments through a propriospinal relay with cell bodies in the C₁-C₂ segments (red). Vagal excitation primarily excites spinothalamic tract neurons in C₁-C₂ and inhibits spinothalamic tract neurons in T₁-T₅.