Effects of gustatory nerve transection and/or ovariectomy on oral capsaicin avoidance in rats.
The incidence of chronic oral pain such as burning mouth syndrome is greater in peri-menopausal females, and was postulated to be associated with gustatory nerve damage. We investigated whether bilateral transection of the chorda tympani, with or without accompanying ovariectomy, affected oral capsaicin avoidance in rats. Female rats had restricted access to 2 bottles, 1 bottle containing capsaicin (concentration range: 0.33-33 μM/L) and the other vehicle. Percent volume of capsaicin consumption and lick counts were measured. The concentration series was tested before and 0.5, 3, 6, 9, and 12 months after the following surgical procedures: (a) bilateral transection of the chorda tympani (CTx); (b) ovariectomy (OVx); (3) CTx plus OVx; or (4) sham CT surgery. Before surgery there was a concentration-dependent decrease in licks and volume of capsaicin consumed, with a threshold between 0.1 and 0.3 ppm. The majority of drink licks occurred during the first 9 minutes of access. Over the 12-month test period, the CTx group did not exhibit reduced capsaicin consumption, and consumed significantly more capsaicin at 6 and 9 months postsurgery. Rats in the OVx group consistently consumed significantly less capsaicin and exhibited significantly higher counts of capsaicin-evoked Fos-like immunoreactivity in the dorsomedial trigeminal subnucleus caudalis (Vc) compared to all other treatment groups. That CTx, with or without OVx, did not enhance capsaicin avoidance indicates that damage to the gustatory system does not disinhibit trigeminal nociceptive transmission.
Department of Neurobiology, Physiology and Behavior, University of California, Davis, CA, USA UFR d'odontologie, University Paris Diderot, Paris, France Department of Food Science and Technology, The Ohio State University, Columbus, OH, USA.
Yves
Y
Boucher
Christopher T
CT
Simons
Mirela Iodi
MI
Carstens
E
E
Carstens
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002211:Capsaicin / Q000633:toxicity*; D002755:Choice Behavior / Q000502:physiology; D002814:Chorda Tympani Nerve / Q000502:physiology* / Q000601:surgery; D004305:Dose-Response Relationship, Drug; D004327:Drinking Behavior / Q000187:drug effects / Q000502:physiology; D005157:Facial Pain / Q000139:chemically induced* / Q000503:physiopathology; D005260:Female; D008297:Male; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D010052:Ovariectomy; D051381:Rats; D018689:Sensory System Agents / Q000633:toxicity*; D013997:Time Factors
D016761:Oncogene Proteins v-fos; D018689:Sensory System Agents; D002211:Capsaicin
Capsaicin avoidance; Chorda tympani; Fos Expression; Hyperalgesia; Nucleus of solitary tract; Ovariectomy; Taste nerve; Trigeminal subnucleus caudalis