	Figure 1: The effect of different intracellular concentrations of the Ca²⁺ chelator BAPTA on the ability of D_2S and D_2L receptor activation to reduce the whole-cell K⁺ current present in NG108-15 cells. BAPTA was varied in the patch pipette at the concentrations shown and allowed to dialyze into the cell for at least 4 minutes after formation of the whole-cell patch configuration . Each data point represents the mean (+SEM) percent reduction in peak outward current observed at a test membrane potential of +70 mV (holding potential was -60 mV) and in the presence of the D₂ receptor agonist QUIN (20 micromolar). It may be observed that the ability of D_2S, but not D_2L , receptor stimulation to decrease whole-cell K⁺ current was attenuated by increases in intracellular BAPTA concentration. *p<0.05, analysis of variance and Bonferroni t-test
	Figure 2: The effects on alterations in [Ca²⁺]_i on the coupling of D_2L receptors to whole-cell K⁺ current. It may be seen that bath application of ryanodine (RYAN 20 micromolar, left panel) or thapsigargin (THAPS 50 micromolar, right panel) had no effect on the K⁺ current observed in this cells. The inset whole-cell current and voltage traces are representative traces from a single cell in both treatment conditions. The cells were held at a membrane potential of -60 mV and stepped to a test potential of +70 mV for a duration of 300 msec. Data represents the mean +SEM for the individual cells studied (N=7 for both groups). Current trace calibration bar represents 1000 pA.
	Figure 3: Bar graph illustrating the effect of bath application of the D₂ receptor agonists quinpirole (QUIN) on [Ca²⁺]_i in transfected NG108-15 cells. It may be observed that in NG108-15 cells stably expressing either the D_2L or the D_2S receptor, QUIN application (50 micromolar) produced an increase in [Ca²⁺]_i relative to control (C). In contrast, there was no effect of QUIN application on wild-type cells. Each bar represents the mean +SEM [Ca²⁺]_i calculated for the group (number above each bar represents the number of cells sampled). *p<0.05, analysis of variance and Bonferroni t-test.
	Figure 4: Photomicrographs demonstrating the mobilization of intracellular calcium upon stimulation of D_2L receptors stably expressed in NG108-15 cells. The pictures represent pseudocolor images of the ratio of the fluorescence intensity measured at 340 and 380 nm. The top panel show the resting calcium levels in several NG108-15 cells. The bottom panel shows the same cells two minutes after bath application of the D₂ receptor agonist quinpirole (20 micromolar). It may be observed that every cell in the field studied demonstrated an increase in [Ca²⁺]_i as indicated by a shift in color from blue towards yellow-red (the relative concentration of calcium is indicated by the calibration bar, see text for details).
	Figure 5: Bar graph illustrating the ability of ryanodine to block the increase in [Ca²⁺]_i which normally accompanies stimulation of D₂ receptors. In both D_2L and D_2S expressing NG108-15 cells QUIN application (50 micromolar) produced a significant increase in [Ca²⁺]_i relative to control levels (C). Ryanodine blocked the observed increase in both transfected groups (RYAN + QUIN). Each bar represents the mean +SEM [Ca²⁺]_i calculated for the group (number above each bar represents the number of cells sampled). *p<0.05, analysis of variance and Bonferroni t-test.
	Figure 6: Bar graph illustrating the ability of pertussis toxin pretreatment to block the increase in [Ca²⁺]_i which normally accompanies stimulation of D_2S receptors. In both D_2L and D_2S expressing NG108-15 cells QUIN application (50 micromolar) produced a significant increase in [Ca²⁺]_i relative to control levels (C). Pretreatment with pertussis toxin (PTX + QUIN) blocked the observed increase in D_2S but not D_2L transfected NG108-15 cells. Each bar represents the mean +SEM [Ca²⁺]_i calculated for the group (number above each bar represents the number of cells sampled). *p<0.05, analysis of variance and Bonferroni t-test.