Volume 129, Issue 5, Pages 1557-1566 (November 2005) 5-HT7 Receptors Modulate Peristalsis and Accommodation in the Guinea Pig Ileum  Marcello Tonini, Riccardo Vicini, Elisabetta Cervio, Fabrizio De Ponti, Roberto De Giorgio, Giovanni Barbara, Vincenzo Stanghellini, Antonio Dellabianca, Catia Sternini  Gastroenterology  Volume 129, Issue 5, Pages 1557-1566 (November 2005) DOI: 10.1053/j.gastro.2005.08.005 Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 1 5-HT7 receptor immunoreactivity in (A) myenteric neurons and in a (B) circular smooth muscle cell in whole mounts of the guinea pig ileum. Calibration bars: (A) 5 μm and (B) 100 μm. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 2 (A) 5-HT7 receptor and (B) NeuN immunoreactivity in neurons of the guinea pig ileum myenteric plexus. (C) Simultaneous localization of 5-HT7 receptor and NeuN immunoreactivities. Arrows indicate myenteric neurons containing both 5-HT7 receptor and NeuN immunoreactivities. Confocal images of cryostat sections. Single optical sections. Calibration bar: 10 μm. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 3 (A) 5-HT7 receptor and (B) NeuN immunoreactivity in neurons of the guinea pig ileum submucosal plexus. (C) Simultaneous localization of 5-HT7 receptor and NeuN immunoreactivities in a submucosal neuron. Confocal images of cryostat sections. Single optical sections. Calibration bar: 5 μm. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 4 Confocal images of cultured myenteric neurons of guinea pig ileum showing (A) NSE immunoreactivity in the cytoplasm of myenteric neurons and (B) 5-HT7 receptor immunoreactivity at the cell surface. (C) Simultaneous localization of 5-HT7 receptor and NSE immunoreactivities. Calibration bars: 20 μm. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 5 Confocal images of cultured myenteric neurons of guinea pig ileum showing (A and D) NeuN or calbindin immunoreactivity in the cytoplasm of myenteric neurons and (B and E) 5-HT7 receptor immunoreactivity at the cell surface. (C and F) Simultaneous localization of 5-HT7 receptor and NeuN or calbindin immunoreactivities. Calibration bars: 16 μm. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 6 Confocal images of cultured myenteric neurons of guinea pig ileum showing (A and D) nNOS and VIP immunoreactivity in the cytoplasm of myenteric neurons and (B and E) 5-HT7 receptor immunoreactivity at the cell surface. (C and F) Simultaneous localization of 5-HT7 receptor and nNOS immunoreactivities or 5-HT7 receptor and VIP immunoreactivities. Arrows point to examples of neurons that contain 5-HT7 receptor and nNOS or VIP. Calibration bars: nNOS and 5-HT7 receptor, 20 μm; VIP and 5-HT7 receptor, 16 μm. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 7 (A) Effect of SB-269970 (100 nmol/L) on threshold and residual pressure (threshold pressure and residual pressure, respectively, expressed in Pa) at different times of contact. Control (n = 8) indicates pressure values in the absence of drug. SB-269970 did not affect residual pressure but significantly increased threshold pressure, triggering peristalsis after 60 (n = 8, **P < .001) and 90 minutes (n = 8, *P < .05). Data are expressed as means ± SEM. (B) Effect of SB-269970 (100 nmol/L) on threshold and residual volume (threshold volume and residual volume, expressed in μL) at different times of contact. Control (n = 8) indicates volume values in the absence of drug treatment. SB-269970 did not affect threshold volume or residual volume after 30, 60, and 90 minutes. Data are expressed as means ± SEM. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 8 Effect of SB-269970 (100 nmol/L) on circular muscle accommodation (μL/Pa) at different times of contact. Control (n = 8) indicates accommodation values in the absence of drug treatment. SB-269970 significantly decreased intestinal accommodation after 60 (n = 8, *P < .05) and 90 minutes of contact (n = 8, *P < .05). Data are expressed as means ± SEM. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 9 Diagram showing the localization of 5-HT7 receptors on AH neurons, descending pathways, and smooth muscle cells. The stimulation of 5-HT7 receptors by endogenous 5-HT released from EC cells induced an overall activation of AH neurons and descending pathways, leading to a nitrergic smooth muscle relaxation. 5-HT released by descending serotonergic interneurons also may participate in the activation of 5-HT7 receptors located on descending NO/VIP interneurons and short descending NO/VIP motor neurons involved in the accommodation of the circular muscle. Finally, 5-HT released by EC cells directly may activate inhibitory 5-HT7 receptors on smooth muscle cells, thus contributing to the relaxation of the circular muscle. Gastroenterology 2005 129, 1557-1566DOI: (10.1053/j.gastro.2005.08.005) Copyright © 2005 American Gastroenterological Association Terms and Conditions