Eric L Rohrs1, Heidi E Kloefkorn2, Emily H Lakes3, Brittany Y Jacobs4, John K Neubert5, Robert M Caudle6, Kyle D Allen7. 1. J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive Biomedical Sciences Building, JG56, Gainesville, FL, 32610, United States. Electronic address: Rohrs.eric@ufl.edu. 2. J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive Biomedical Sciences Building, JG56, Gainesville, FL, 32610, United States. Electronic address: hkloefkorn@ufl.edu. 3. J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive Biomedical Sciences Building, JG56, Gainesville, FL, 32610, United States; Institute for Cell Engineering and Regenerative Medicine, University of Florida, Gainesville, FL, United States. Electronic address: elakes@ufl.edu. 4. J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive Biomedical Sciences Building, JG56, Gainesville, FL, 32610, United States. Electronic address: starjacobs@ufl.edu. 5. Department of Orthodontics, University of Florida, Gainesville, FL, United States; Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, United States. Electronic address: jneubert@dental.ufl.edu. 6. Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, United States; Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, United States. Electronic address: caudle@ufl.edu. 7. J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, 1275 Center Drive Biomedical Sciences Building, JG56, Gainesville, FL, 32610, United States; Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, United States; Institute for Cell Engineering and Regenerative Medicine, University of Florida, Gainesville, FL, United States; Nanoscience Institute for Medical and Engineering Technology, University of Florida, Gainesville, FL, United States. Electronic address: kyle.allen@bme.ufl.edu.
Abstract
BACKGROUND: Detecting behaviors related to orofacial pain in rodent models often relies on subjective investigator grades or methods that place the animal in a stressful environment. In this study, an operant-based behavioral assay is presented for the assessment of orofacial tactile sensitivity in the rat. NEW METHODS: In the testing chamber, rats are provided access to a sweetened condensed milk bottle; however, a 360° array of stainless steel wire loops impedes access. To receive the reward, an animal must engage the wires across the orofacial region. Contact with the bottle triggers a motor, requiring the animal to accept increasing pressure on the face during the test. To evaluate this approach, tolerated bottle distance was measured for 10 hairless Sprague Dawley rats at baseline and 30 min after application of capsaicin cream (0.1%) to the face. The experiment was repeated to evaluate the ability of morphine to reverse this effect. RESULTS: The application of capsaicin cream reduced tolerated bottle distance measures relative to baseline (p<0.05). As long as morphine did not cause reduced participation due to sedation, subcutaneous morphine dosing reduced the effects of capsaicin (p<0.001). Comparison with existing method: For behavioral tests, experimenters often make subjective decisions of an animal's response. Operant methods can reduce these effects by measuring an animal's selection in a reward-conflict decision. Herein, a method to measure orofacial sensitivity is presented using an operant system. CONCLUSIONS: This operant device allows for consistent measurement of heightened tactile sensitivity in the orofacial regions of the rat.
BACKGROUND: Detecting behaviors related to orofacial pain in rodent models often relies on subjective investigator grades or methods that place the animal in a stressful environment. In this study, an operant-based behavioral assay is presented for the assessment of orofacial tactile sensitivity in the rat. NEW METHODS: In the testing chamber, rats are provided access to a sweetened condensed milk bottle; however, a 360° array of stainless steel wire loops impedes access. To receive the reward, an animal must engage the wires across the orofacial region. Contact with the bottle triggers a motor, requiring the animal to accept increasing pressure on the face during the test. To evaluate this approach, tolerated bottle distance was measured for 10 hairless Sprague Dawley rats at baseline and 30 min after application of capsaicin cream (0.1%) to the face. The experiment was repeated to evaluate the ability of morphine to reverse this effect. RESULTS: The application of capsaicin cream reduced tolerated bottle distance measures relative to baseline (p<0.05). As long as morphine did not cause reduced participation due to sedation, subcutaneous morphine dosing reduced the effects of capsaicin (p<0.001). Comparison with existing method: For behavioral tests, experimenters often make subjective decisions of an animal's response. Operant methods can reduce these effects by measuring an animal's selection in a reward-conflict decision. Herein, a method to measure orofacial sensitivity is presented using an operant system. CONCLUSIONS: This operant device allows for consistent measurement of heightened tactile sensitivity in the orofacial regions of the rat.
Authors: Todd A Nolan; Jordan Hester; Yvonne Bokrand-Donatelli; Robert M Caudle; John K Neubert Journal: Behav Brain Res Date: 2010-10-23 Impact factor: 3.332