Extracellular calcium sensed by a novel cation channel in hippocampal neurons.
Extracellular concentrations of Ca2+ change rapidly and transiently in the brain during excitatory synaptic activity. To test whether such changes in Ca2+ can play a signaling role we examined the effects of rapidly lowering Ca2+ on the excitability of acutely isolated CA1 and cultured hippocampal neurons. Reducing Ca2+ excited and depolarized neurons by activating a previously undescribed nonselective cation channel. This channel had a single-channel conductance of 36 pS, and its frequency of opening was inversely proportional to the concentration of Ca2+. The inhibition of gating of this channel was sensitive to ionic strength but independent of membrane potential. The ability of this channel to sense Ca2+ provides a novel mechanism whereby neurons can respond to alterations in the extracellular concentration of this key signaling ion.
Xiong
Z
Z
Department of Physiology, University of Toronto, Toronto, Canada M5S 1A8.
Lu
W
W
MacDonald
J F
JF
D000818:Animals; D002118:Calcium / Q000502:physiology*; D004594:Electrophysiology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007473:Ion Channels / Q000032:analysis / Q000502:physiology*; D051379:Mice; D009431:Neural Conduction / Q000502:physiology; D009474:Neurons / Q000502:physiology*
D007473:Ion Channels; D002118:Calcium