Comment

The mammalian intestinal tract when isolated in vitro remains a complex integrated system of musculature, secretory epithelium, blood vasculature, and enteric nervous system that may be influenced by release of mediators from enteroendocrine cells and elements of the enteric immune/inflammatory system. When isolated in vitro the small and large intestine is therefore amenable to study at multiple levels of biological organisation. Stevens et alinvestigated fluorometric changes in Ca²⁺ in a window (∼1 mm²) of longitudinal muscle, myenteric plexus and presumed network of interstitial cells of Cajal exposed by dissection in a 4 cm-long flat sheet preparation of guinea pig distal colon and extrapolated their observations to mixing and propulsive motility in the whole gut.

The results confirm the critical importance of Ca²⁺ in excitation–contraction coupling in smooth muscle and as a charge carrier in the generation of action potentials in both the muscle and myenteric neurones. Calcium waves, as mentioned in the title, are presumed to be a reflection of the propagation of muscle action potentials and associated muscle contraction. The authors’ descriptions of the spread of the Ca²⁺ waves in the 1 mm² patch of tissue and collisions of waves as they spread into the same region from opposite directions show in another format the well known functional syncytial properties of intestinal smooth muscle and cell-to-cell electrical conduction across gap junctions in this tissue.

The authors’ conclusions, drawn for whole organ …