Contribution of Ca²⁺-Dependent Cl⁻ Channels to Norepinephrine-Induced Contraction of Femoral Artery Is Replaced by Increasing EDCF Contribution during Ageing

Table 4

Pharmacodynamic parameters of norepinephrine concentration-response curves determined in individual femoral arteries isolated from 20-month-old WKY rats in the presence of R(+)-IAA-94 (IAA, Ca²⁺-dependent Cl⁻ channel blocker) and indomethacin (IME, cyclooxygenase inhibitor) as well as in the presence of niflumic acid (NIFLU, cyclooxygenase inhibitor, and Cl⁻ channel blocker).

	Parameters	Control (𝑛=16)	IAA (𝑛=8)	IME (𝑛=8)	NIFLU (𝑛=8)
WKY	EC50 (log mol/L)	−5.22 ± 0.12	−5.89 ± 0.10^a	−4.67 ± 0.18^b	−4.93 ± 0.18^b
	𝐸max (mN/mm)	6.79 ± 0.20	6.86 ± 0.26	1.40 ± 0.10^a,b	1.18 ± 0.06^a,b
	Slope	3.90 ± 0.37	4.49 ± 0.35	0.43 ± 0.10^a,b	0.63 ± 0.09^a,b

Data are presented as mean ± S.E.M.; ^a𝑃<0.05 versus control; ^b𝑃<0.05 versus IAA.