Ca2+-activated Cl− channels as Ca2+ sensors with particular reference to the modulation of neuronal excitability

Abstract

Publisher Summary This chapter discusses the function, significance, and activation of Ca 2+ -activated Cl – channels. A variety of neurons express Ca 2+ -activated Cl – channels that open in response to an increase in intracellular Ca 2+ ([Ca 2+ ] i ) and mediate a Ca 2+ -activated Cl – current [ I Cl ( Ca )]. Such currents are described in central nervous system (CNS) neurons from the spinal cord and hippocampus, sympathetic and parasympathetic neurons, and neurons from sensory systems, including olfactory, photoreceptor, trigeminal, and dorsal root ganglion (DRG) neurons. Ca 2+ -activated Cl – channels may be expressed in a limited subset of these neurons. The opening of Ca 2+ -activated Cl – channels shift the membrane potential toward the equilibrium potential for Cl – (E Cl ) established by the Cl – transport mechanisms of the neuron. These mechanisms vary among neurons expressing Ca 2+ -activated Cl – channels. The distribution of Cl – varies among different neurons; hence, the effect of activating Ca 2+ -activated Cl – channels also varies. The activation of Cl – conductance stabilizes the resting potential of neurons where Cl‑ is passively distributed or hyperpolarizes neurons that actively extrude Cl – .