Membrane conductances of mouse cone photoreceptors.
Animals
Calcium
/ metabolism
Cyclic GMP
/ metabolism
Female
Ion Channel Gating
/ physiology
Ion Channels
/ metabolism
Male
Membrane Potentials
/ physiology
Mice
Potassium
/ metabolism
Retina
/ metabolism
Retinal Cone Photoreceptor Cells
/ metabolism
Retinal Rod Photoreceptor Cells
/ metabolism
Voltage-Dependent Anion Channels
/ metabolism
Journal
The Journal of general physiology
ISSN: 1540-7748
Titre abrégé: J Gen Physiol
Pays: United States
ID NLM: 2985110R
Informations de publication
Date de publication:
02 03 2020
02 03 2020
Historique:
received:
24
10
2019
revised:
20
12
2019
accepted:
20
12
2019
entrez:
28
1
2020
pubmed:
28
1
2020
medline:
8
6
2021
Statut:
ppublish
Résumé
Vertebrate photoreceptor cells respond to light through a closure of CNG channels located in the outer segment. Multiple voltage-sensitive channels in the photoreceptor inner segment serve to transform and transmit the light-induced outer-segment current response. Despite extensive studies in lower vertebrates, we do not know how these channels produce the photoresponse of mammalian photoreceptors. Here we examined these ionic conductances recorded from single mouse cones in unlabeled, dark-adapted retinal slices. First, we show measurements of the voltage dependence of the light response. After block of voltage-gated Ca2+ channels, the light-dependent current was nearly linear within the physiological range of voltages with constant chord conductance and a reversal potential similar to that previously determined in lower vertebrate photoreceptors. At a dark resting membrane potential of -45 mV, cones maintain a standing Ca2+ current (iCa) between 15 and 20 pA. We characterized the time and voltage dependence of iCa and a calcium-activated anion channel. After constitutive closure of the CNG channels by the nonhydrolysable analogue GTP-γ-S, we observed a light-dependent increase in iCa followed by a Ca2+-activated K+ current, both probably the result of feedback from horizontal cells. We also recorded the hyperpolarization-activated cyclic nucleotide-gated (HCN) conductance (ih) and measured its current-voltage relationship and reversal potential. With small hyperpolarizations, ih activated with a time constant of 25 ms; activation was speeded with larger hyperpolarizations. Finally, we characterized two voltage-gated K+-conductances (iK). Depolarizing steps beginning at -10 mV activated a transient, outwardly rectifying iK blocked by 4-AP and insensitive to TEA. A sustained iK isolated through subtraction was blocked by TEA but was insensitive to 4-AP. The sustained iK had a nearly linear voltage dependence throughout the physiological voltage range of the cone. Together these data constitute the first comprehensive study of the channel conductances of mouse photoreceptors.
Identifiants
pubmed: 31986199
pii: 133655
doi: 10.1085/jgp.201912520
pmc: PMC7054858
pii:
doi:
Substances chimiques
Ion Channels
0
Voltage-Dependent Anion Channels
0
Cyclic GMP
H2D2X058MU
Potassium
RWP5GA015D
Calcium
SY7Q814VUP
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Subventions
Organisme : NEI NIH HHS
ID : P30 EY000331
Pays : United States
Organisme : NEI NIH HHS
ID : R37 EY001844
Pays : United States
Organisme : Intramural NIH HHS
ID : Z01 EY000311
Pays : United States
Organisme : NEI NIH HHS
ID : T32 EY007026
Pays : United States
Organisme : NEI NIH HHS
ID : R01 EY001844
Pays : United States
Informations de copyright
© 2020 Ingram et al.
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