Ion channels in airway afferent neurons.

Action potentials initiated at the peripheral terminal of an afferent nerve are conducted to the central nervous system therein causing release of neurotransmitters that excite secondary neurons in the brain stem or spinal cord. Various chemicals, extremes in osmolarity and pH as well as mechanical stimuli are sensed by primary afferent nerves that innervate the airways. The processes leading to excitation of afferent nerve endings, conduction of action potentials along axons, transmitter secretion, and neuronal excitability are regulated by ions flowing through channels in the nerve membrane. Voltage-gated ion channels selective for K+ and Na+ ions allow the generation and conduction of action potentials and along with families of ion channels selective for other ions such as Ca2+ or Cl- are thought to play distinctive roles in regulating neuronal excitability and transmitter secretion. Here we discuss, in general terms, the roles played by various classes of ion channels in the activation, neurotransmitter secretion and excitability of primary afferent neurons.