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

Table 2

Pharmacodynamic parameters of norepinephrine concentration-response curves determined in individual femoral arteries isolated from adult and aged WKY and SHR which were studied under the control conditions (CONTROL), in the presence of N^ω-nitro-L-arginine (L-NNA, NO synthase inhibitor) and in the presence of R(+)-IAA-94 (IAA, Ca²⁺-dependent Cl⁻ channel blocker) as well as in the presence of IAA and L-NNA (IAA + L-NNA).

	Parameters	Adult WKY (6 months)	Aged WKY (12 months)	Adult SHR (6 months)	Aged SHR (12 months)
CONTROL; (6/7/6/9)	EC50 (log mol/L)	−4.93 ± 0.09	−5.11 ± 0.13	−5.12 ± 0.15	−5.43 ± 0.08
	𝐸max (mN/mm)	5.26 ± 0.84	5.30 ± 0.64	8.25 ± 0.32^a	10.41 ± 0.70^b,c
	Slope	3.69 ± 0.55	3.11 ± 0.77	11.27 ± 0.52^a	8.80 ± 1.10^c
L-NNA; (6/7/6/7)	EC50 (log mol/L)	−5.84 ± 0.13^d,e	−6.14 ± 0.07^d,e	−6.17 ± 0.04^d,e	−6.28 ± 0.07^d,e
	𝐸max (mN/mm)	10.48 ± 0.70^d,e	7.29 ± 0.30^a,d,e	11.31 ± 0.54^d,e	12.63 ± 0.78^c,d,e
	Slope	10.03 ± 1.60^d	9.77 ± 1.84	12.24 ± 0.46	15.71 ± 3.12
IAA; (6/7/6/9)	EC50 (log mol/L)	−5.53 ± 0.13^d	−5.79 ± 0.13^d,e	−5.35 ± 0.05	−5.48 ± 0.07
	𝐸max (mN/mm)	0.15 ± 0.05^d	0.53 ± 0.08^d	1.68 ± 0.20^a,d,e	4.66 ± 0.60^b,c,d,e
	Slope	2.63 ± 0.78	1.68 ± 0.12	9.50 ± 1.96	21.12 ± 7.04
IAA + L-NNA; (6/7/6/7)	EC50 (log mol/L)	−5.42 ± 0.12^d	−5.47 ± 0.08^d	−5.28 ± 0.02	−5.46 ± 0.07^b
	𝐸max (mN/mm)	0.76 ± 0.03^d	1.64 ± 0.38^d	4.21 ± 0.52^a,d	9.17 ± 0.90^b,c
	Slope	2.00 ± 0.77	6.29 ± 3.20	18.40 ± 4.49^a	14.03 ± 0.76

Data are presented as mean ± S.E.M., the number of vessels studied under different experimental conditions is indicated in parentheses (adult WKY/aged WKY/adult SHR/aged SHR). Significant differences: ^a𝑃<0.05 versus adult WKY; ^b𝑃<0.05 versus adult SHR; ^c𝑃<0.05 versus aged WKY; ^d𝑃<0.05 versus Control; ^e𝑃<0.05 versus IAA + L-NNA.