5-Hydroxytryptamine4 receptor agonists initiate the peristaltic reflex in human, rat, and guinea pig intestine  John R. Grider, Amy E. Foxx-Orenstein, Ji-Guang Jin  Gastroenterology  Volume 115, Issue 2, Pages 370-380 (August 1998) DOI: 10.1016/S0016-5085(98)70203-3 Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 1 Concentration-response curves for the effect of HTF 919 on (A) CGRP, (B) SP, and (C) VIP release in guinea pig and rat colonic segments. HTF 919 was added to the central compartment, and the release of all three peptides was measured in all compartments (see Materials and Methods for details). The increase in CGRP occurred only in the central compartment, the increase in SP occurred only in the peripheral orad compartment, and the increase in VIP occurred only in the peripheral caudad compartment. Results are expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of 4–8 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 1 Concentration-response curves for the effect of HTF 919 on (A) CGRP, (B) SP, and (C) VIP release in guinea pig and rat colonic segments. HTF 919 was added to the central compartment, and the release of all three peptides was measured in all compartments (see Materials and Methods for details). The increase in CGRP occurred only in the central compartment, the increase in SP occurred only in the peripheral orad compartment, and the increase in VIP occurred only in the peripheral caudad compartment. Results are expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of 4–8 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 1 Concentration-response curves for the effect of HTF 919 on (A) CGRP, (B) SP, and (C) VIP release in guinea pig and rat colonic segments. HTF 919 was added to the central compartment, and the release of all three peptides was measured in all compartments (see Materials and Methods for details). The increase in CGRP occurred only in the central compartment, the increase in SP occurred only in the peripheral orad compartment, and the increase in VIP occurred only in the peripheral caudad compartment. Results are expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of 4–8 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 2 CGRP release induced by HTF 919 in humans, guinea pigs, and rats in the presence and absence of hexamethonium. HTF 919 (0.1 μmol/L; 2) was added to the central compartment alone or after a 10-minute treatment with hexamethonium (100 μmol/L; ▨). CGRP release is expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of three experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 3 Effect of selective 5-HT antagonists on (A) CGRP, (B) SP, and (C) VIP release induced by HTF 919 in segments of human jejunum and rat and guinea pig colon. Sampling of peptides is as detailed in Figure 1. HTF 919 (2) was added to the mucosa at a maximally effective concentration of 1 μmol/L. Release of all three peptides was not affected by the selective 5-HT3 antagonist LY 278584 (▨) but was virtually abolished by the mixed 5-HT4/5-HT3 antagonist SDZ 205557 (■). Results are expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of 3–8 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 3 Effect of selective 5-HT antagonists on (A) CGRP, (B) SP, and (C) VIP release induced by HTF 919 in segments of human jejunum and rat and guinea pig colon. Sampling of peptides is as detailed in Figure 1. HTF 919 (2) was added to the mucosa at a maximally effective concentration of 1 μmol/L. Release of all three peptides was not affected by the selective 5-HT3 antagonist LY 278584 (▨) but was virtually abolished by the mixed 5-HT4/5-HT3 antagonist SDZ 205557 (■). Results are expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of 3–8 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 3 Effect of selective 5-HT antagonists on (A) CGRP, (B) SP, and (C) VIP release induced by HTF 919 in segments of human jejunum and rat and guinea pig colon. Sampling of peptides is as detailed in Figure 1. HTF 919 (2) was added to the mucosa at a maximally effective concentration of 1 μmol/L. Release of all three peptides was not affected by the selective 5-HT3 antagonist LY 278584 (▨) but was virtually abolished by the mixed 5-HT4/5-HT3 antagonist SDZ 205557 (■). Results are expressed as fmol · 100 mg−1 · min−1. Values are means ± SE of 3–8 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 4 Concentration-response curves for the effect of HTF 919 on (A) ascending contraction and (B) descending relaxation in guinea pig colonic segments in the presence and absence of selective 5-HT antagonists. HTF 919 was added to the central compartment; ascending contraction was measured in the peripheral orad compartment, and descending relaxation was measured in the peripheral caudad compartment. Responses were not affected by the selective 5-HT3 antagonist LY 278584 but were inhibited by the selective 5-HT4 antagonist GR 113808A and the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of 3–10 experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 5 Concentration-response curves for the effect of HTF 919 on (A) ascending contraction and (B) descending relaxation in rat colonic segments in the presence and absence of selective 5-HT antagonists. HTF 919 was added to the central compartment; ascending contraction was measured in the peripheral orad compartment, and descending relaxation was measured in the peripheral caudad compartment. Responses were not affected by the selective 5-HT3 antagonist LY 278584, but they were inhibited by the selective 5-HT4 antagonist GR 113808A and the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of 3–8 experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 6 Tracings illustrating (A) ascending (orad) contraction and (B) descending (caudad) relaxation of rat colon preparation in response to HTF 919 (1 nmol/L to 1 μmol/L). Asterisks denote addition of HTF 919 to the central compartment. Measurements of response were made in the peripheral orad and caudad compartments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 7 The effect of HTF 919 on (A) ascending contraction and (B) descending relaxation in human jejunal segments in the presence and absence of selective 5-HT antagonists. HTF 919 (1 μmol/L) was added to one compartment of a two-compartment preparation, and ascending contraction or descending relaxation was measured in the other compartment. The responses were not affected by the selective 5-HT3 antagonist LY 278584 but were inhibited by the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of three experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 8 Concentration-response curves for the effect of RO93877 on (A) ascending contraction and (B) descending relaxation in guinea pig colonic segments in the presence and absence of selective 5-HT antagonists. R093877 was added to the central compartment; ascending contraction was measured in the peripheral orad compartment, and descending relaxation was measured in the peripheral caudad compartment. Responses were not affected by the selective 5-HT3 antagonist LY 278584, but they were inhibited by the selective 5-HT4 antagonist GR 113808A and the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of 3–6 experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 8 Concentration-response curves for the effect of RO93877 on (A) ascending contraction and (B) descending relaxation in guinea pig colonic segments in the presence and absence of selective 5-HT antagonists. R093877 was added to the central compartment; ascending contraction was measured in the peripheral orad compartment, and descending relaxation was measured in the peripheral caudad compartment. Responses were not affected by the selective 5-HT3 antagonist LY 278584, but they were inhibited by the selective 5-HT4 antagonist GR 113808A and the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of 3–6 experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 9 Concentration-response curves for the effect of R093877 on (A) ascending contraction and (B) descending relaxation in rat colonic segments in the presence and absence of selective 5-HT antagonists. R093877 was added to the central compartment; ascending contraction was measured in the peripheral orad compartment, and descending relaxation was measured in the peripheral caudad compartment. Responses were not affected by the selective 5-HT3 antagonist LY 278584, but they were inhibited by the selective 5-HT4 antagonist GR 113808A and the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of 3–8 experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 9 Concentration-response curves for the effect of R093877 on (A) ascending contraction and (B) descending relaxation in rat colonic segments in the presence and absence of selective 5-HT antagonists. R093877 was added to the central compartment; ascending contraction was measured in the peripheral orad compartment, and descending relaxation was measured in the peripheral caudad compartment. Responses were not affected by the selective 5-HT3 antagonist LY 278584, but they were inhibited by the selective 5-HT4 antagonist GR 113808A and the mixed 5-HT4/5-HT3 antagonist SDZ 205557. Results are expressed in grams of force. Values are means ± SE of 3–8 experiments. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 10 Effect of the selective CGRP antagonist hCGRP8-37 on (A) ascending contraction and (B) descending relaxation elicited by HTF 919 in segments of human jejunum and rat and guinea pig colon. ■, HTF 919; ●, + hCGRP8-37. HTF was added to the mucosa at a maximal concentration of 1 μmol/L. The responses in all three species were inhibited by 75%–80% by hCGRP8-37 (10 μmol/L). Results were expressed in grams of force. Values are means ± SE of 3–4 experiments in each species. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 11 Model depicting extrinsic and intrinsic sensory pathways mediating the peristaltic reflex. The extrinsic pathway is activated by muscle stretch and consists of CGRP neurons with cell bodies in the dorsal root ganglion. The intrinsic pathway is activated by mucosal stimuli and consists of CGRP neurons with cell bodies in the enteric nervous system and afferent projections to the mucosa. Mucosal stimuli release 5-HT from enterochromaffin cells that acts on 5-HT4 receptors (in humans and rats) and both 5-HT4 and 5-HT3 receptors (in guinea pigs) located on the nerve terminals of intrinsic CGRP neurons. Whether extrinsic or intrinsic, CGRP neurons relay sensory stimuli to the same populations of interneurons coupled to excitatory cholinergic and tachykinin motor neurons and inhibitory VIP, PACAP, and NO synthase motor neurons. Gastroenterology 1998 115, 370-380DOI: (10.1016/S0016-5085(98)70203-3) Copyright © 1998 American Gastroenterological Association Terms and Conditions