Ca²⁺/cAMP-sensitive covariation of I(A) and I(H) voltage dependences tunes rebound firing in dopaminergic neurons.
The level of expression of ion channels has been demonstrated to vary over a threefold to fourfold range from neuron to neuron, although the expression of distinct channels may be strongly correlated in the same neurons. We demonstrate that variability and covariation also apply to the biophysical properties of ion channels. We show that, in rat substantia nigra pars compacta dopaminergic neurons, the voltage dependences of the A-type (I(A)) and H-type (I(H)) currents exhibit a high degree of cell-to-cell variability, although they are strongly correlated in these cells. Our data also demonstrate that this cell-to-cell covariability of voltage dependences is sensitive to cytosolic cAMP and calcium levels. Finally, using dynamic clamp, we demonstrate that covarying I(A) and I(H) voltage dependences increases the dynamic range of rebound firing while covarying their amplitudes has a homeostatic effect on rebound firing. We propose that the covariation of voltage dependences of ion channels represents a flexible and energy-efficient way of tuning firing in neurons.
Institut National de la Santé et de la Recherche Médicale UMR1072, Marseille 13015, France.
Julien
J
Amendola
Adele
A
Woodhouse
Marie-France
MF
Martin-Eauclaire
Jean-Marc
JM
Goaillard
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000502:physiology*; D059290:Dopaminergic Neurons / Q000502:physiology*; D005260:Female; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D008297:Male; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D015220:Calcium Channels; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015221:Potassium Channels; D000242:Cyclic AMP; D002118:Calcium