Chem. Senses 26: 491-497,
2001
© Oxford University Press 2001
An Animal Model to Assess Aversion to Intra-oral Capsaicin: Increased Threshold in Mice Lacking Substance P
1 Section of Neurobiology, Physiology and Behavior and 2 Department of Food Science and Technology, University of California—Davis, 1 Shields Avenue, Davis, CA 95616, USA
Correspondence to be sent to: E. Carstens, Section of Neurobiology, Physiology and Behavior, University of California—Davis, 1 Shields Avenue, Davis, CA 95616, USA. e-mail: eecarstens{at}ucdavis.edu
Despite the widespread consumption of products containing chemicals that irritate the oral mucosa, little is known about the underlying neural mechanisms nor is there a corresponding animal model of oral irritation. We have developed a rodent model to assess aversion to capsaicin in drinking water, using a paired preference paradigm. This method was used to test the hypothesis that the neuromodulator substance P (SP) plays a role in the detection of intra-oral capsaicin. ‘Knockout’ (KO) mice completely lacking SP and neurokinin A due to a disruption of the preprotachykinin A gene and a matched population of wild-type (WT) mice had free access to two drinking bottles, one containing water and the other capsaicin at various concentrations. Both KO and WT mice showed a concentration-dependent aversion to capsaicin. KO mice consumed significantly more capsaicin than WT at a single near threshold (1.65 µM) concentration, indicating that SP plays a limited role in the detection and rejection of oral irritants.
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