Calcium-dependent potassium conductance in the photoresponse of a nudibranch mollusk

Yoram Grossman, Jeffrey A. Schmidt, Daniel L. Alkon

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12 Scopus citations


1. 1. The response to light of Hermissenda photoreceptors when recorded intracellularly without interference from synaptic and action potentials consisted of three phases: an early depolarization (ED) followed by hyperpolarization (dip) and subsequent depolarization (tail). 2. 2. The ED and the dip were associated with increased membrane conductance while decreased membrane conductance was involved with the tail. 3. 3. The dip reversal potential was - 82.1 ± 5.3 mV and its amplitude varied inversely with the log of [K+]. 4. 4. Perfusing with agents which block K+ current like 4AP, Quinine, Quinidine or injection of TEA eliminated the dip and its associated increased membrane conductance, thus further supporting the role of K+ conductance in producing the dip. 5. 5. The dip was enhanced by increased [Ca2+]o, reduced by decreased [Ca2+]o and abolished together with its associated increased membrane conductance when perfused with either D600, Cd2+, Mg2+, Mn2+, or Co2+, which block transmembrane Ca2+ current. 6. 6. The dip and its associated increased membrane conductance were abolished by intracellular injection of EGTA and enhanced by perfusion with Ruthenium red. 7. 7. Intracellular injection of Ca2+ mimicked the dip: membrane conductance was increased and the cell hyperpolarized. 8. 8. These results indicate that the increase in intracellular [Ca2+] is primarily responsible for the light-induced increase of K+ conductance during the dip. The possible source of the Ca2+ is, at least in part, extracellular due to activation of an inward Ca2+ current.

Original languageEnglish
Pages (from-to)487-494
Number of pages8
JournalComparative Biochemistry and Physiology -- Part A: Physiology
Issue number3
StatePublished - 1 Jan 1981

ASJC Scopus subject areas

  • Physiology


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