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The Journal of Neuroscience, August 15, 2001, 21(16):5902-5915

Paradoxical Role of Large-Conductance Calcium-Activated K⁺ (BK) Channels in Controlling Action Potential-Driven Ca²⁺ Entry in Anterior Pituitary Cells

Fredrick Van Goor¹, Yue-Xian Li², and Stanko S. Stojilkovic¹

¹ Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510, and ² Departments of Mathematics and Zoology, University of British Colombia, Vancouver, British Columbia, Canada V6T 1Z2

Activation of high-conductance Ca²⁺-activated K⁺ (BK) channels normally limits action potential duration and the associated voltage-gated Ca²⁺ entry by facilitating membrane repolarization. Here we report that BK channel activation in rat pituitary somatotrophs prolongs membrane depolarization, leading to the generation of plateau-bursting activity and facilitated Ca²⁺ entry. Such a paradoxical role of BK channels is determined by their rapid activation by domain Ca²⁺, which truncates the action potential amplitude and thereby limits the participation of delayed rectifying K⁺ channels during membrane repolarization. Conversely, pituitary gonadotrophs express relatively few BK channels and fire single spikes with a low capacity to promote Ca²⁺ entry, whereas an elevation in BK current expression in a gonadotroph model system leads to the generation of plateau-bursting activity and high-amplitude Ca²⁺ transients.

Key words: somatotrophs; gonadotrophs; bursting; voltage-gated Ca²⁺ channels; delayed rectifier K⁺ channels; domain Ca²⁺

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Copyright © 2001 Society for Neuroscience  0270-6474/01/21165902-14$05.00/0

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