Figure 4.

Cardiovascular responses to R-PIA (10⁻¹⁰ – 3×10⁻⁷ mol kg⁻¹ i.v.) in anaesthetized guinea-pig in the absence and in the presence of DPCPX (0.1 mg kg⁻¹ i.v.). Each point in the curves is the mean·±s.e. of 4 – 6 experiments; ^*: P⩽0.05. Values are reported as per cent of resting mean blood pressure (BP) or heart rate (HR) just prior to starting the agonist dose-response curve: 52.7±4.1 mmHg and 355.8±17.1 beats min⁻¹ (control); 44.8±1.8 mmHg and 342.5±15.2 beats min⁻¹ (DPCPX-treated).