Calcium is necessary for light excitation in barnacle photoreceptors

✍ Scribed by Uri Werner; Edith Suss-Toby; Ayelet Rom; Baruch Minke

• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 807 KB
• Volume: 170
• Category: Article
• ISSN: 0340-7594
• DOI: 10.1007/bf00191459

✦ Synopsis

Illumination of barnacle (Balanus amphitrite)

photoreceptors is known to increase the membrane permeability to sodium and Ca 2+ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La a +), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca 2 + by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca 2+, but not K § into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La 3 +. The EGTA experiments suggest that internal Ca 2 + is necessary for light excitation of barnacle photoreceptors while the La 3+ experiments suggest that La a+sensitive inward current is necessary to maintain excitation during prolonged light.