Figure 6.

Effects of PTX, CTX and FR900359, capable of silencing G_i/o, G_s and G_q signalling, respectively, on the quinpirole induced DMR response in CHO-K1 hD_2longR cells. (A,C,E) Representative recordings of the quinpirole (1 μM) induced response of untreated cells (control) and cells pretreated with pertussis toxin (PTX) (A), cholera toxin (CTX) (C) or FR900359 (E). Data were normalised to the maximum change in wavelength shift induced by quinpirole (1 μM) observed in untreated CHO-K1 hD_2longR cells (100%) and a buffer control (0%). (B) Concentration–response curves of quinpirole resulting from DMR measurements in the absence (control) or presence of PTX at different concentrations. Cells were pretreated with PTX for about 20 h. (D) Concentration–response curves of quinpirole resulting from DMR measurements in the absence (control) or presence of CTX at different concentrations. Cells were pretreated with CTX for about 20 h. In the case of blocking G_q signalling by FR900359 (E), cells were incubated with FR900359 for 2 h before the addition of quinpirole and subsequent measurement. Data in (B,D) represent means ± SEM of three independent experiments, each performed in triplicate.