Studies on calcium-activated potassium channel expressed by the neurosecretory cells of Medulla Terminalia X-organ in the eyestalks of Eriocheir sinensis
Inside-out patch clamp technique was used to study the properties of calcium-activated potassium channel(BK Ca)of neurosecretory cells dissociated from Medulla Terminalia X-organ(MTXO) of Chinese mitten crab Eriocheir sinensis. Calcium-activated potassium channel was observerd in symmertrical high potassium solutions (200 mmol•L-1),and the single channel showed rapid-open rectangle waves with different durations and had a conductance of (213.4±11.2) pS. At a series of the membrane potentials (from -80 to +80 mV), the current amplitude and the open state probability of single channel presented obviously voltage-dependent. In addition, the open state probability of single channel also increased in proportion to Ca2+ concentration in the bath solution, indicating that the single channel was obviously sensitive to intracellular free Ca2+ concentration. Furthermore, drug sensitivity testing revealed that tetraethylammonium (TEA, 80 mmol•L-1) could completely block the single channel. The experiments suggested that BKCa channel of neurosecretory cells dissociated from MTXO of Chinese mitten crab Eriocheir sinensis is voltage-dependent with a large conductance and is sensitive to Ca2+ and TEA. Key words: Eriocheir sinensis; medulla terminalia X-organ; neurosecretory cell; calcium-activated potassium channel; patch clamp