TABLE 3

The relationship between GDP concentration and agonist potency

In the experiments at 0.1 nM [³⁵S]GTPγS, all compounds had similar slopes (P > 0.05), with the exception of bromocriptine. In the experiments at 10 nM [³⁵S]GTPγS, the slope for 7-OH-DPAT was different from 0 (P < 0.05) and was different from slopes for other compounds (P < 0.05); the slope for p-tyramine was not different from 0 (P > 0.05), and the slopes for dopamine and NPA were different from those for (±)-7-OH-DPAT and p-tyramine. Slopes for NPA or dopamine were different at the two concentrations of [³⁵S]GTPγS. The slopes of the lines shown in Fig. 5 were determined by linear regression.