Regulation of Guinea pig intestinal peristalsis by endogenous endothelin acting at ETB receptors  Anaid Shahbazian, Peter Holzer  Gastroenterology  Volume 119, Issue 1, Pages 80-88 (July 2000) DOI: 10.1053/gast.2000.8549 Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 1 Recordings of the peristaltic motor action of (A) ET-1 and (B) STX-6c administered to the organ bath at the indicated concentrations. ET-1 stimulated peristalsis as deduced from a decrease of the PPT (dots) and an increase of the peristaltic frequency. STX-6c inhibited peristalsis as deduced from a rise of PPT; in addition, peristalsis became slightly irregular. Gastroenterology 2000 119, 80-88DOI: (10.1053/gast.2000.8549) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 2 Concentration-response relationship for the effect of ET-1, ET-3, STX-6c, and VIC to alter PPT. The concentration-response curves were recorded in a cumulative manner, and the graph shows peak changes in PPT that occurred within 15 minutes after exposure to each agonist concentration. The values represent means ± SEM; n ≥ 5. *P < 0.05, **P < 0.01 vs. PPT recorded before exposure to any drug (Wilcoxon signed-rank test). Gastroenterology 2000 119, 80-88DOI: (10.1053/gast.2000.8549) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 3 Concentration-response relationship for the effect of (A) ET-1 and (B) STX-6c to alter the PPT in the presence of vehicle, BQ-123 (3 μmol/L), or BQ-788 (3 μmol/L), which were administered 30 minutes before the ET-1 and STX-6c concentration-response curves were recorded in a cumulative manner. The values represent means ± SEM; n ≥ 7. *P < 0.05, **P < 0.01 vs. respective values recorded in the presence of vehicle (Kruskal–Wallis H test followed by Mann–Whitney U test). Gastroenterology 2000 119, 80-88DOI: (10.1053/gast.2000.8549) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 4 Effect of hexamethonium on the concentration-dependent action of ET-1 to decrease the PPT. Vehicle or hexamethonium (100 μmol/L) was administered 60 minutes before the concentration-response curve for ET-1 was recorded in a cumulative manner. The values represent means ± SEM; n = 8. *P < 0.05, **P < 0.01 vs. respective values recorded in the presence of vehicle (Mann–Whitney U test). Gastroenterology 2000 119, 80-88DOI: (10.1053/gast.2000.8549) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 5 (A) Recording of the peristaltic motor action of BQ-788 administered to the organ bath at the indicated concentrations. BQ-788 stimulated peristalsis as deduced from a decrease of the PPT (indicated by dots) and an increase of the peristaltic frequency. (B) Cumulative concentration-response relationship for the effect of BQ-788 to lower PPT. The values represent means ± SEM; n = 6. *P < 0.05, **P < 0.01 vs. PPT recorded before exposure to BQ-788 (Wilcoxon signed-rank test). Gastroenterology 2000 119, 80-88DOI: (10.1053/gast.2000.8549) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 6 Diagram showing the putative location of endothelin ETA and ETB receptors in the enteric nerve/muscle circuits governing propulsive peristalsis in the guinea pig small intestine. +, Excitation; −, inhibition; CM, circular muscle; LM, longitudinal muscle; M, muscarinic acetylcholine receptor; MP, myenteric plexus; MU, mucosa; N, nicotinic acetylcholine receptor; NK1, NK2, tachykinin receptor types; P2X, purinoceptor type; VIP, vasoactive intestinal polypeptide. Gastroenterology 2000 119, 80-88DOI: (10.1053/gast.2000.8549) Copyright © 2000 American Gastroenterological Association Terms and Conditions