Figure 8.
Activation of endogenous P2Y purinergic receptors reduces inactivation of ICa in bovine adrenal chromaffin cells. Chromaffin cells were recorded using the amphotericin perforated whole-cell recording configuration to maintain endogenous calcium buffers. The cells were stimulated with a 5 Hz train of APW lasting 15 s first under control conditions and then in the presence of 10 μm extracellular ATP. ATP activates P2Y receptors to produce Gβγ-mediated inhibition of ICa. The extracellular solution contained 2 mm Ca2+ in these experiments. A, Mean peak amplitude of ICa under control conditions and in the presence of ATP is plotted against time for the duration of the APW train (n = 5). The inset shows four currents from a representative cell. These currents were elicited by the first and last APW of the train under control conditions and in the presence of ATP. (Note that for display clarity, error bars are not shown for every data point.) B, The same data as in A except the amplitude of ICa is normalized to the first pulse within each train. ATP significantly reduced inactivation during the train of APW (p < 0.003). Error bars indicate SEM.