Figure 4. Asynchronicity between δ-cells and between δ- and β-cells.

A, fluorescence records in response to a change from 3 to 11 mM glucose in 8 cells of an islet of Langerhans. Note that the stimulating glucose concentration (11 mM) induces synchronous oscillations in traces 1-5. Traces 6-8 represent cells with an oscillatory behaviour in the presence of 3 mM glucose. These cells were completely asynchronized and independent of glucose concentration. B, the cross-correlation (C-C) function from cells 3 and 4 clearly shows an oscillatory behaviour and a central peak, confirming the presence of highly correlated oscillatory events. Cell 3 was the reference cell. A cross-correlation function with any of the other cells (1-5) gave the same result. C, the cross-correlation function from cells 6 and 7 shows the absence of correlated events, confirming the total asynchronicity of δ-cells. Cell 6 was the reference cell. The cross-correlation function from cell 6 and cells 1-4 confirmed the absence of correlated events between δ-cells and β-cells.