Figure 7.

2-methyl-thio-ATP decreases the Δ[Ca²⁺]_v plateau during long trains of impulses whereas neither α,β-methylene ATP nor adenosine has much effect. (a–c) show the effects on Δ[Ca²⁺]_v of stimulating with long trains of impulses (10 Hz for 30 s) in the presence of 2-methyl-thio-ATP (100 μM), α,β-methylene ATP (100 μM) and adenosine (200 μM) respectively. (d–f) give the changes in the size of Δ[Ca²⁺]_v in the presence of 2-methyl-thio-ATP, α,β-methylene ATP and adenosine respectively for a number of varicosities. Each symbol gives the average changes in the amplitude of Δ[Ca²⁺]_v in the presence of the drug plotted against the average value of Δ[Ca²⁺]_v for the same varicosity in the control solution.