ABSTRACT
Aim To investigate the selective inhibition of ethanol on muscarinic receptor-or 5-HT receptor-me-diated contractile responses in the circular smooth mus-cle strips isolated from the different regions of rat stom-ach. Methods Circular muscle strips isolated from the rat gastric fundus, body, cardia and pylorus were prepared, and the contractile responses to carbachol ( CCh ) or 5-HT were recorded. Results Ethanol (0. 000 05~0. 000 5, V/V) did not affect the contrac-tile response to CCh in circular muscle strips from the rat gastric fundus and cardia, and that to 5-HT in the strips from rat gastric fundus and body ( P >0. 05 ) . However, ethanol(0. 000 1 and 0. 000 5) significantly inhibited the Emax value of the contraction by CCh from (12. 18 ± 0. 33) g of control level to (10. 88 ± 0. 41) g and -lgEC50 value from ( 6. 33 ± 0. 05 ) of control level to (6. 12 ± 0. 06)(P <0. 05) in the strips from rat gastric body. Ethanol(0. 000 1 and 0. 000 5) also significantly inhibited the Emax value of the contraction by CCh from (2. 87 ± 0. 15) g of control level to (2. 2 ± 0. 13) g and -lgEC50 value from (6. 49 ± 0. 10) of control level to (6. 05 ± 0. 09)(P<0. 01) in the strips from rat gastric pylorus. Moreover, ethanol ( 0. 000 1 and 0. 000 5) significantly inhibited the Emax value of the contraction by 5-HT from (2. 93 ± 0. 35) g of con-trol level to ( 2. 1 ± 0. 30 ) g ( P<0. 05 ) , but did not affect the -lgEC50 value in the strips from rat gastric cardia. Conclusions Ethanol inhibits the contractile responses to 5-HT only in the circular muscle strips of rat gastric cardia, and it inhibits the contractile respon-ses to CCh more strongly in the circular muscle strips of gastric pylorus than gastric body. In those gastric circular muscle strips, ethanol decreases both the ac-tivity and affinity of CCh to muscarinic receptors, but decreases only the activity of 5-HT to its receptors.
ABSTRACT
Aim To investigate the role of endothe-lium in the enhancement of phenylephrine-mediated vasoconstriction by bupivacaine in the isolated rat aor-ta.Methods The isolated rat aortic rings were pre-pared, and the vascular endothelium was removed chemically or physically .Phenylephrine-mediated vas-oconstriction was recorded .Results A pretreatment with bupivacaine at 30 μmol · L-1 for 20 min signifi-cantly increased the Emax value of vasoconstrictive re-sponses to phenylephrine from 2.22 ±0.07 g of sol-vent-controlled group to 2.50 ±0.05 g ( P0.05 ) .A pretreatment with bupivacaine at 30 μmol · L-1 for 20 min slightly but significantly inhibited the vasoconstrictive responses to low concen-tration of phenylephrine in the isolated endothelium-de-nuded rat aorta (P0.05 ) .Conclusion Bupivacaine enhances α1-adre-noceptor-mediated vasoconstriction by inhibiting vascu-lar endothelium in the isolated endothelium-intact rat aorta, Which potentiates indirectly the vasoconstrictive responses to phenylephrine .