Figure 2.

Pharmacological characterization of the receptor mediating the enhancement of [³H]-noradrenaline release. SCG cell cultures were treated with pertussis toxin (PTX; 100 ng·mL⁻¹ for 24 h) and were labelled with [³H]-noradrenaline and superfused. Subsequent to a 60 min washout period, 4 min fractions of superfusate were collected, and tritium overflow was evoked by electrical field stimulation as shown in Figure 1A. (A) The concentration-dependent increase in the S2/S1 ratio of tritium overflow caused by ADP, ATP or 2-MesATP (n = 6 to 13). Nucleotides used at the concentrations indicated or the appropriate solvent were present from minute 88 onwards. (B) The increase in the S2/S1 ratio caused by the indicated concentrations of ADP as percentage of control in the absence or presence of the indicated concentrations (in µM) of suramin (n = 8–9), reactive blue 2 (RB2; n = 10–12) or MRS 2179 (n = 8–9). P-values for the significance of differences between the results obtained in the absence and presence of antagonists are indicated above the bars.