Fig. 3.

Comparison of outward K ^± channel currents before and after administration of iberiotoxin (IBTX) and 4-aminopyridine (4-AP) in VSMCs isolated from cerebral arteries of FHH and FHH.1^BN rats. Whole-cell K⁺ currents were recorded from freshly dissociated cerebral VSMCs from FHH and FHH.1^BN rats at 1 μM free cytosolic calcium [Ca²⁺]_i in the presence and absence of IBTX and IBTX + 4-AP. Current-voltage curves presenting peak K⁺ channel current density (pA/pF) in FHH rats (n = 9) and FHH.1^BN rats (n = 8) are presented in A and B. C and D: summary graphs of the absolute, IBTX, and 4-AP-sensitive outward K⁺ channel current densities (pA/pF) in FHH and FHH.1^BN rats at +100 mV. Note IBTX alone decreased a greater percentage of K⁺ current densities in FHH rats as compared with FHH.1^BN congenic strain, whereas IBTX + 4-AP application decreased similar percentage of K⁺ current densities in FHH and FHH.1^BN rats. *Significant difference in the corresponding values measured in FHH rats. Mean values ± SE are presented.