Figure 3. Representative tracings of arterial diameter demonstrating the contrasting vasomotor effects of calcium ionophore A23187 (31.6 to 316 nM) (left) and thrombin (1 U ml⁻¹) (right) on isolated carotid arteries from newborn (P1) (top) and P21 (bottom) mice .

Arteries were analysed in a microperfusion system at a P _TM of 20 mmHg and responses to thrombin and A23187 were assessed during constriction with U46619 (U4). A downward movement in the trace indicates constriction, with the dashed line representing 100% constriction (or 0% baseline diameter). Blue traces represent control arteries, whereas the red traces represent paired arteries treated with endothelin ET_A and ET_B receptor antagonists (BQ123 1 μm plus BQ788 1 μm).