Relationship between depression of Kv and excitability of TRG neurons under trigeminal neuropathic/inflammatory conditions. A: The operational component of primary sensory neurons (1st) includes a peripheral terminal that innervates target tissues and transduces sensory stimuli. An axon conducts action potentials from the periphery to the central nervous system via the cell body in the trigeminal ganglion and central terminal, from where information is transferred to second order neurons (2nd) at the central synapse (e.g., trigeminal spinal nucleus). B: The relationship between the depression of Kv channels and the excitability of TRG neurons. The increases in action potential firing and duration prolongs the opening of voltage-gated Ca2+ channels (Cav), potentiating Ca2+ influx, and causing an increase in neurotransmitter released from the cell bodies and nerve terminals. These changes can alter the properties of trigeminal pain pathways.