J Neurogastroenterol Motil 2019; 25(2): 300-315  
Fluoroscopic Characterization of Colonic Dysmotility Associated to Opioid and Cannabinoid Agonists in Conscious Rats
Susana Díaz-Ruano,1 Ana E López-Pérez,1,5 Rocío Girón,2,3,4,5 Irene Pérez-García,2 María I Martín-Fontelles,2,3,4,5 and Raquel Abalo2,3,4,5*
1Unidad de Dolor, Servicio de Anestesiología, Hospital General Universitario Gregorio Marañón, Madrid, Spain; 2Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain; 3Unidad Asociada I+D+i al Instituto de Investigación en Ciencias de la Alimentación, CIAL (CSIC), Madrid, Spain; 4Unidad Asociada I+D+i al Instituto de Química Médica, IQM (CSIC), Madrid, Spain; and 5Grupo de Excelencia Investigadora URJC-Banco de Santander-Grupo Multidisciplinar de Investigación y Tratamiento del Dolor (i+DOL), Madrid, Spain
Correspondence to: *Raquel Abalo, PhD
Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Avda. de Atenas s/n, 28922 Alcorcón, Madrid, Spain, Tel: +34-91-488-8854, Fax: +34-91-488-8955, E-mail: raquel.abalo@urjc.es
Susana Díaz-Ruano and Ana E López-Pérez have contributed equally to this manuscript.
Received: December 3, 2018; Revised: February 1, 2019; Accepted: February 12, 2019; Published online: April 30, 2019.
© The Korean Society of Neurogastroenterology and Motility. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background/Aims: Gastrointestinal adverse effects have a major impact on health and quality of life in analgesics users. Non-invasive methods to study gastrointestinal motility are of high interest. Fluoroscopy has been previously used to study gastrointestinal motility in small experimental animals, but they were generally anesthetized and anesthesia itself may alter motility. In this study, our aim is to determine, in conscious rats, the effect of increasing doses of 2 opioid (morphine and loperamide) and 1 cannabinoid (WIN 55,212-2) agonists on colonic motility using fluoroscopic recordings and spatio-temporal maps.
Methods: Male Wistar rats received barium sulfate intragastrically, 20-22 hours before fluoroscopy, so that stained fecal pellets could be seen at the time of recording. Animals received an intraperitoneal administration of morphine, loperamide, or WIN 55,212-2 (at 0.1, 1, 5, or 10 mg/kg) or their corresponding vehicles (saline, Cremophor, and Tocrisolve, respectively), 30 minutes before fluoroscopy. Rats were conscious and placed within movement-restrainers for the length of fluoroscopic recordings (120 seconds). Spatio-temporal maps were built, and different parameters were analyzed from the fluoroscopic recordings in a blinded fashion to evaluate colonic propulsion of endogenous fecal pellets.
Results: The analgesic drugs inhibited propulsion of endogenous fecal pellets in a dose-dependent manner.
Conclusions: Fluoroscopy allows studying colonic propulsion of endogenous fecal pellets in conscious rats. Our method may be applied to the non-invasive study of the effect of different drug treatments and pathologies.
Keywords: Analgesics, opioids; Cannabinoids; Colonic motility; Fluoroscopy; Rats


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