Premium
Modulation of the synaptic Ca 2+ current in salamander photoreceptors by polyunsaturated fatty acids and retinoids
Author(s) -
Vellani Vittorio,
Reynolds A. Martyn,
McNaughton Peter A.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00333.x
Subject(s) - retinal , biology , epoxygenase , arachidonic acid , docosahexaenoic acid , polyunsaturated fatty acid , biophysics , biochemistry , neurotransmission , microbiology and biotechnology , fatty acid , enzyme , receptor
1 Synaptic transmission between retinal photoreceptors and second‐order neurones is controlled by an L‐type Ca 2+ conductance ( g Ca ) in the photoreceptor inner segment. Modulation of this conductance therefore influences the flow of visual information to higher centres. 2 Possible modulation of g Ca by retinal factors was investigated using patch clamp and Ca 2+ imaging. No significant modulation of g Ca by retinal neurotransmitters nor by intracellular signalling pathways was found. 3 gCa was inhibited by retinoids (all‐ trans retinal) and by polyunsaturated fatty acids (PUFAs) such as arachidonic acid and docosahexaenoic acid, which are known to be released in the retina by exposure to light. 4 Some PUFAs tested are physiological substrates for the cyclo‐oxygenase, lipoxygenase and epoxygenase pathways, but specific inhibitors of these pathways had no effect on the inhibition of g Ca . 5 Treatments designed to activate or inhibit G‐protein‐coupled pathways or protein kinases A and C similarly had no effect on the inhibition by PUFAs nor on g Ca itself. Inhibitors of phosphatases 1 and 2A were also largely ineffective. 6 The inhibition by PUFAs is, however, dependent on membrane potential, suggesting that it arises from a direct interaction of fatty acids with the Ca 2+ channel. The effect was not use or frequency dependent, suggesting that the effect does not depend on channel gating state. 7 Control by retinoids and by PUFAs may be an important mechanism by which the Ca 2+ conductance, and consequently the transmission of the visual signal, is modulated at the first retinal synapse.