A potassium contribution to the response of the barnacle photoreceptor.
1. Intracellular recording from photoreceptors in the lateral eye of the barnacle show a brief negative-going 'dip' shortly after the onset of the late receptor potential. This phase can sometimes result in a hyperpolarization relative to the resting membrane potential. 2. The dip is prominent in light-adapted cells and is reduced by dark-adaptation. Low extracellular Ca2+ also reduces it. 3. The amplitude of the dip changes inversely with the K+ concentration in the saline. 4. The amplitude of the dip depends on the membrane potential, with a reversal potential near - 80 mV. 5. K+ blocking agents such as quinine and quinidine reduce or abolish the dip. 6. These observations indicate that the dip is due to a brief increase in K+ conductance which may be dependent on an influx of Ca ions. The fast decay of this phase may be brought about by a rapid uptake of Ca2+ by an intracellular mechanism.
D000221:Adaptation, Ocular; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010786:Photoreceptor Cells / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology / Q000502:physiology*; D011802:Quinidine / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D001468:Thoracica / Q000502:physiology*
D011803:Quinine; D011802:Quinidine; D011188:Potassium; D002118:Calcium