Light-evoked calcium responses of isolated melanopsin-expressing retinal ganglion cells

Andrew T.E. Hartwick, Jayne R. Bramley, Jianing Yu, Kelly T. Stevens, Charles N. Allen, William H. Baldridge, Patricia J. Sollars, Gary E. Pickard

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

A small number (<2%) of mammalian retinal ganglion cells express the photopigment melanopsin and are intrinsically photosensitive (ipRGCs). Light depolarizes ipRGCs and increases intracellular calcium levels ([Ca 2+]i) but the signaling cascades underlying these responses have yet to be elucidated. To facilitate physiological studies on these rare photoreceptors, highly enriched ipRGC cultures from neonatal rats were generated using anti-melanopsin-mediated plate adhesion (immunopanning). This novel approach enabled experiments on isolated ipRGCs, eliminating the potential confounding influence of rod/cone-driven input. Light induced a rise in [Ca2+]i (monitored using fura-2 imaging) in the immunopanned ipRGCs and the source of this Ca2+ signal was investigated. The Ca2+ responses were inhibited by 2-aminoethoxydiphenyl borate, SKF-96365 (1-2-(4-methoxyphenyl)-2-[3-(4- methoxyphenyl)propoxy]ethyl-1H-imidazole), flufenamic acid, lanthanum, and gadolinium, consistent with the involvement of canonical transient receptor potential (TRP) channels in ipRGC phototransduction. However, the contribution of direct Ca2+ flux through a putative TRP channel to ipRGC [Ca 2+]i was relatively small, as most (∼90%) of the light-induced Ca2+ responses could be blocked by preventing action potential firing with tetrodotoxin. The L-type voltage-gated Ca2+ channel (VGCC) blockers verapamil and (+)-cis-diltiazem significantly reduced the light-evoked Ca2+ responses, while the internal Ca2+ stores depleting agent thapsigargin had negligible effect. These results indicate that Ca2+ influx through VGCCs, activated after action potential firing, was the primary source for light-evoked elevations in ipRGC [Ca2+]i. Furthermore, concurrent Ca2+ imaging and cell-attached electrophysiological recordings demonstrated that the Ca 2+ responses were highly correlated to spike frequency, thereby establishing a direct link between action potential firing and somatic [Ca 2+]i in light-stimulated ipRGCs.

Original languageEnglish (US)
Pages (from-to)13468-13480
Number of pages13
JournalJournal of Neuroscience
Volume27
Issue number49
DOIs
StatePublished - Dec 5 2007

Fingerprint

Retinal Ganglion Cells
Calcium
Light
Action Potentials
Transient Receptor Potential Channels
1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
Flufenamic Acid
Light Signal Transduction
Lanthanum
Vertebrate Photoreceptor Cells
Thapsigargin
Diltiazem
Fura-2
Tetrodotoxin
Gadolinium
Verapamil
melanopsin

Keywords

  • Calcium
  • Circadian rhythms
  • Melanopsin
  • Retinal ganglion cell
  • TRP channel
  • Voltage-gated calcium channels

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Hartwick, A. T. E., Bramley, J. R., Yu, J., Stevens, K. T., Allen, C. N., Baldridge, W. H., ... Pickard, G. E. (2007). Light-evoked calcium responses of isolated melanopsin-expressing retinal ganglion cells. Journal of Neuroscience, 27(49), 13468-13480. https://doi.org/10.1523/JNEUROSCI.3626-07.2007

Light-evoked calcium responses of isolated melanopsin-expressing retinal ganglion cells. / Hartwick, Andrew T.E.; Bramley, Jayne R.; Yu, Jianing; Stevens, Kelly T.; Allen, Charles N.; Baldridge, William H.; Sollars, Patricia J.; Pickard, Gary E.

In: Journal of Neuroscience, Vol. 27, No. 49, 05.12.2007, p. 13468-13480.

Research output: Contribution to journalArticle

Hartwick ATE, Bramley JR, Yu J, Stevens KT, Allen CN, Baldridge WH et al. Light-evoked calcium responses of isolated melanopsin-expressing retinal ganglion cells. Journal of Neuroscience. 2007 Dec 5;27(49):13468-13480. https://doi.org/10.1523/JNEUROSCI.3626-07.2007
Hartwick, Andrew T.E. ; Bramley, Jayne R. ; Yu, Jianing ; Stevens, Kelly T. ; Allen, Charles N. ; Baldridge, William H. ; Sollars, Patricia J. ; Pickard, Gary E. / Light-evoked calcium responses of isolated melanopsin-expressing retinal ganglion cells. In: Journal of Neuroscience. 2007 ; Vol. 27, No. 49. pp. 13468-13480.
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