YFa and analogs: Investigation of opioid receptors in smooth muscle contraction

Table 1 IC₅₀ values for inhibition of smooth muscle contraction induced by YFa and its analogs in guinea pig ileum and mouse vas deferens assays

Guinea pig ileum (n = 9)a			Mouse vas deferens (n = 9)a
Agonist	IC50 (μmol/L)	P value	Agonist	IC50 (μmol/L)	P value
Morphine	4.40	0.001	Morphine	13.41	0.001
Dyn A (1-13)	33.8	0.004	Dyn A (1-13)	ns	-
YFa	ns	-	YFa	7.10	0.001
D (Ala-2) YFa	12.0	0.001	D (Ala-2) YFa	0.20	0.0006
(Des-Phe) YFa	14.9	0.0002	(Des-Phe) YFa	ns	-
MERF-COOH	3.71	0.005	MERF-COOH	5.51	0.0005
MERF-NH2	ns	-	MERF-NH2	ns	-

^aP < 0.05 for guinea pig ileum and mouse vas deferens assays was considered statistically significant. The values represent mean ± SE for three experiments performed in triplicate. IC₅₀ values were calculated by one-way ANOVA and data were statistically significant. MERF: Methionine-enkephalin-Arg6-Phe7. ns: Non-significant.