Figure 1. Pancreatic lobule preparation: penetration of applied substances into deep layers .

Experiment illustrating the difficulties of attaining the full concentration level deep inside the pancreatic tissue of substances applied to the surface of a lobule. A, [Ca²⁺]_i traces obtained from PACs at different depths from the surface of the lobule (signposted by the colour coding shown). Responses to ACh (10 μm), carbachol (CCh) (10 μm) and CCK (10 nm) are shown. B, transmitted light image of the lobule from which the recordings shown in A were obtained. The different recording positions are indicated using the colour coding shown in A.