FIGURE 11.

A: schematic of electrical coupling between β-cells in an intact islet. The green rectangles indicate gap junctions. Electrically coupled cells are indicated in pink. One β-cell within the islet is voltage-clamped at −70 mV through the recording electrode, so inhibiting electrical activity. Spontaneous electrical activity in neighboring electrically coupled cells (black traces in pink cells) results in an inward current in the voltage-clamped cell that resembles an inverted burst of action potentials. B: membrane potential (top) and membrane current (bottom) recorded from the same β-cell under current- and voltage-clamp conditions, respectively. Assuming that electrical activity recorded in the β-cell connected to the patch electrode before voltage-clamping approximates that of its neighbors, the total gap-junctional conductance (G_j) can be estimated from the equation G_j = ΔI/ΔV, where ΔV (above) and ΔI (below) represent the current and voltage differences between the plateau current/potential and the most repolarized voltage/least negative current. C: an example of bursting electrical activity where low-amplitude action potentials (coming from an adjacent β-cell) precede full-amplitude action potentials (red rectangle). These low-amplitude action potentials probably reflect electrical activity in a neighboring β-cell(s) that ‟leaksˮ into the cell from which the recording is made via gap junctions.