Purinergic Signalling (2006) 2:545–557 549 Fig. 2 Concentration-response relationships for the [Ca]in increases in response to ATP and ATP analogues. A) Representative [Ca]in increases induced by various concentrations of ATP in the presence of 2 mM external Ca2+. B) Averaged concentration–response relationships for ATP and ATP analogues. All responses were normalized to the mean of two control responses induced by 100 mM ATP before and after the test response. Each point is the mean T S.E.M. of data from ﬁve to nine neurons. MeS-ATP: 2-methylthio- ATP. Table 1 Effects of P2 receptor antagonists and Ca2+ channel blockers on the [Ca]in increases induced by ATP and high K+-saline Stimulus ATP100 M 110 mMKCl ATP100 M Blockers Suramin 10 M 20 M 50 M PPADS 10 M 20 M 50 M 100 M Nitrendipine 2 M jCT.M C 2 M jCT.M A 2 M jCT.M A 2 M + jCT.M C 2 M Nitrendipine 2 M Nicardipine 2 M Cd2+ 50 M jCT.M A 2 M + jCT.M C 2 M Percent of control 55 T 7 (N = 5) 30 T 5 (N = 6) 13 T 3 (N = 5) 96 T 6 (N = 3) 70 T 8 (N = 9) 25 T 5 (N = 6) 11 T 5 (N = 4) 44 T 4 (N = 16) 61 T 4 (N = 16) 62 T 6 (N = 16) 58 T 5 (N = 10) 56 T 4 (N = 21) 47 T 9 (N = 10) 27 T 3 (N = 14) 77 T 9 (N = 4) The mean [Ca]in increase induced by the ﬁrst and third applications of ATP (100 mM) or 110 mM KCl were averaged and referred to as 100%, and the response in the presence of the P2 antagonist or Ca2+ channel blocker was expressed as a percentage of this control value. The cell was pre-treated for 30 s with the indicated agent before the second stimulation with 100 mM ATP or 110 mM KCl. Number of experiments is shown in parentheses. w-CT w-conotoxin.