Modification of voltage-sensitive inactivation of Na+current by external Ca2+in the marine dinoflagellateNoctiluca miliaris

✍ Scribed by K. Oami; Y. Naitoh; T. Sibaoka

• Book ID: 104658087
• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 453 KB
• Volume: 176
• Category: Article
• ISSN: 0340-7594
• DOI: 10.1007/bf00192492

✦ Synopsis

Effects of the external Ca 2+ concentration on the depolarization-induced transient inward Na § current responsible for the Na § spike in the dinoflagellate Noctiluca miliaris were examined. The peak value and the duration of the Na § current increased when lowering the external Ca 2 § concentration. The threshold potential level for activation and the reversal potential level of the current were not affected by the external Ca 2+ concentration. The inactivation took place even in a solution containing EGTA with very low (< 10-9M) Ca 2+ concentration. Voltage dependency of the inactivation was scarcely affected by the external Ca 2 § concentration. It is concluded that inactivation of Na § channels responsible for the current is dependent on membrane depolarization and that the external Ca 2 § modulates the inactivation kinetics. Appearance of a Na § spike in a solution with reduced Ca 2+ concentration is caused by a lowered rate of inactivation of the Na § channels.