Figure 3.

Original trace monitoring the rat MMA diameter during one of the in vivo levcromakalim protocols. Vertically, the arbitrary unit scale from the video dimension analyser tracks the MMA diameter throughout the experiment. H:min:s timescale inserted below the trace. Real-time images above the trace show the maximal levcromakalim-induced dilatation of the rat MMA (marked by the white arrows) before (left image) and after (right image) PNU-37883A inhibition. The arrow below each image points to the spot on the trace when the image was captured. The experimental protocol used in the study (see trace): (a) saline bolus, (b) first infusion of levcromakalim (0.025 mg kg⁻¹), (c) infusion of PNU-37883A (0.5 mg kg⁻¹), (d) second infusion of levcromakalim (0.025 mg kg⁻¹). Note from the profile of the trace that besides the reduction in peak dilatation of the MMA, we generally observed that the duration of the dilatation was shortened after PNU-37883A inhibition and that the onset of dilatory responses was delayed after the second dose of levcromakalim was infused. These observations were also apparent in the pinacidil and P-1075 protocols. MMA, middle meningeal artery.