Figure 7. Interactions between caffeine and adenosine.

A, relationship between adenosine concentration and caffeine-induced release. Mean (± s.e.m.) amplitude of the caffeine-induced Ca²⁺ transient in the absence and presence of 2, 5 or 10 mm adenosine. All responses were obtained in the presence of 5 mm ATP using the protocol shown in Fig. 6A. The number of preparations is indicated in parentheses. B, ATP dependence of adenosine-induced release inhibition. Each point is the mean (± s.e.m.) amplitude of the caffeine-induced Ca²⁺ transient in the presence or absence of 5 mm adenosine, at 5 (□) or 10 mm (▪) ATP. All results are expressed relative to the mean response in the presence of 5 mm ATP, 0 mm adenosine. The number of preparations is indicated in parentheses.