Oscillation of [Ca²⁺]_i-linked K⁺ conductance in bullfrog sympathetic ganglion cell is sensitive to intracellular anions

Abstract

The intracellular free Ca²⁺ ([Ca²⁺]_i) regulates the K⁺ conductance (G_K) of the many types of cell membrane^1–11. The Ca²⁺ influx during an action potential activates this [Ca²⁺]_i-linked G_K in most neurones^2–4,8–11. In caffeine-treated sympathetic ganglion cells, however, Ca²⁺ released from an intracellular Ca²⁺ reservoir site analogous to the sarcoplasmic reticulum (SR) of the muscle (see ref. 12) causes activation of the G_K, which results in slow oscillatory hyperpolarisations (caffeine hyperpolarisation, C-hyperpolarisation)¹¹. Such a release of Ca²⁺ linked to the G_K of the membrane seems important for understanding the role of the intracellular organelles in the control of membrane activities of a neurone. We report here the mechanism of the slow oscillatory hyperpolarisations recorded from the bullfrog sympathetic ganglion cell in Ringer solution. It is found that these hyperpolarisations are generated by a [Ca²⁺]_i-linked G_K system and are highly sensitive to anions in an intracellular recording electrode, probably to intracellular anions.