English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Visual excitation in rhabdomeric photoreceptors is thought to be mediated by activation of a light-regulated phospholipase C (PLC) and the consequent hydrolysis of phosphatidylinositol bisphosphate. Whereas much attention has been devoted to inositol trisphosphate (IP3) production and intracellular Ca2+ release, little is known about the possible role of the DAG branch in the generation of the light response. We have tested the effect of chemically distinct surrogates of DAG on isolatedLima photoreceptors. Application of the phorbol ester PMA (0.5–10 μm) or the alkaloid (−)-indolactam (20–100 μm) from a holding potential of −50 mV elicited an inward current, several hundred picoamperes in amplitude, accompanied by a pronounced increase in membrane conductance. The stereoisomers 4α-PMA and (+)-indolactam were both inactive, arguing for the specificity of the effects. Elevation of cytosolic Ca2+ by intracellular dialysis accelerated this current, whereas chelerythrine antagonized it, suggesting the involvement of PKC. The reversal potential of the membrane current induced by PKC activators was approximately +10 mV; replacement of extracellular Na with impermeantN-methyl-d-glucamine decreased its amplitude and shifted the reversal potential in the negative direction. Stimulation by PMA and (−)-indolactam was accompanied by a pronounced depression of light responsiveness; conversely, steady illumination reduced the size of the current elicited by these PKC activators. Taken together, these results support the notion that the DAG branch of the PLC cascade, in addition to its suggested participation in visual adaptation, may play a role in the activation of the photoresponse or a component thereof, probably in synergy with IP3-mediated Ca2+ release.

Membrane Current Induced by Protein Kinase C Activators in Rhabdomeric Photoreceptors: Implications for Visual Excitation