Two Types of Voltage-activated Calcium Currents in Goldfish Horizontal Cells
Two Types of Voltage-activated Calcium Currents in Goldfish Horizontal Cells
- Sun-Sook Paik Sun-Ho Bai Chang-Sub Jung
- 대한생리학회-대한약리학회
- The Korean Journal of Physiology & Pharmacology
- 제9권 제5호
- 등재여부 : KCI등재
- 2005.01
- 269 - 274 (6 pages)
In horizontal cells (HCs) that were freshly dissociated from goldfish retina, two types of voltage- dependent calcium currents (I<SUB>Ca</SUB>) were recorded using a patch-clamping configuration: a transient type current and a sustained type current. The cell was held at ⁣40 mV, and the prepulse step of ⁣90 mV was applied before command pulse between ⁣65 and ⁢55 mV. The transient Ca<SUP>2⁢</SUP> current was activated by depolarization to around ⁣50 mV from a prepulse voltage of ⁣90 mV lasting at least 400 ms and reached a maximal value near ⁣25 mV. On the other hand, the sustained Ca<SUP>2⁢</SUP> current was induced by pre-inactivation for less than 10 ms duration. Its activation started near ⁣10 mV and peaked at ⁢20 mV. Co<SUP>2⁢</SUP> (2 mM) suppressed both of these two components, but nifedipine (20μM), L-type Ca<SUP>2⁢</SUP> channel antagonist, blocked only the sustained current. Based on the activation voltage and the pharmacological specificity, the sustained current appears to be similar to L-type I<SUB>Ca</SUB> and the transient type to T-type I<SUB>Ca</SUB>. This study is the first to confirm that transient type I<SUB>Ca</SUB> together with the sustained one is present in HCs dissociated from goldfish retina.