Patch-clamp recordings in isolated sponge cells (Axinella polypoides)

Sponges are the most ancient known metazoans. Their cells are specialised but not organised into tissues or organs. Recordings of action potential-like propagating electrical impulses suggested that electrical signalling may occur between sponge cells, but the characterization of ionic channels in these cells is still at the beginning. Actually, sponge cell surfaces are covered by a complex glycocalyx and long-chain fatty acids are present in the lipid core of their membranes. In these experimental conditions, a low percentage of tight seals (3%) was obtained applying the patch-clamp technique to cells isolated from the Mediterranean Demospongia Axinella polypoides. This paper shows in detail how difficulties can be overcome making use of trivalent cations in the extracellular solution and how electrophysiological measurements can be performed on sponge cell membranes. A potassium selective conductance is shown as an example. We suggest that the presented methodology could also be applied to other cell types.