Hydrocortisone and dexamethasone increase intercellular communication in salivary glands of Chironomus thummi larvae

The effects of hydrocortisone (HC) and dexamethasone (DX) on intercellular electrical coupling and fluorescent dye diffusion through intercellular channels in the salivary gland cells of Chironomus thummi larvae were studied electrophysiologically. The observed electrical coupling ratios between adjacent cells in freshly excised salivary glands were widespread, ranging from 0.5 to 1.0. When HC (10 micrograms/ml) and DX (0.25 micrograms/ml) were applied to gland cells with low electrical coupling ratios (below 0.5), the coupling ratio between adjacent cells increased to 1.0 in 60 min and the resting membrane potentials were stable. The calculated junctional conductance increased fivefold, while non-junctional conductance decreased to a fifth of the starting levels. Fluorescein dye, injected into originally impermeable gland cells, was found in adjacent cells one hour after HC application. It is suggested that HC and DX acted by opening the gates of the intercellular channels.