Intracellular calcium ions decrease the affinity of the GABA receptor.
Intracellular free Ca2+ [( Ca2+]i) plays a crucial role in the transduction of extracellular signals. It has been implicated in the modulation of light sensitivity in Limulus photoreceptors and in the efficacy of synaptic transmission; calcium ion fluxes are also involved in the postsynaptic facilitation of nicotinic transmission seen in sympathetic ganglia, and in activation of the acetylcholine (ACh) receptor. [Ca2+]i is also a second messenger for many biologically active substances. We recorded neuronal activities of sensory neurones from the bullfrog (Rana catesbiana), using the suction pipette method and a 'concentration clamp' technique to apply gamma-aminobutyric acid (GABA) to the cell. We report the first evidence that [Ca2+]i suppresses the GABA-activated Cl- conductance, by decreasing the apparent affinity of the GABA receptor.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D005727:Ganglia, Spinal / Q000502:physiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D011892:Rana catesbeiana; D011963:Receptors, GABA-A / Q000502:physiology*; D012964:Sodium / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D002712:Chlorides; D007473:Ion Channels; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D012964:Sodium; D002118:Calcium