Mustard oil has differential effects on the response of trigeminal caudalis neurons to heat and acidity.
Topical application of mustard oil (allyl isothiocyanate) to the skin or injection into joints induces hyperalgesia, allodynia, and neuroinflammation. However, when applied to the oral or nasal mucosa, mustard oil evokes a desensitizing pattern of irritation. Presently we investigated the responses of neurons in superficial laminae of trigeminal subnucleus caudalis (Vc) to noxious thermal (53 degrees C) and chemical (pentanoic acid; 200 mM) stimuli prior to and following lingual mustard oil application. A low concentration of mustard oil (0.125%) applied by constant flow (0.5 ml/min; 15 min), initially excited Vc neurons followed by partial desensitization. Responses to noxious heat were unchanged following mustard oil. A high concentration of mustard oil (1.25%) initially excited Vc neurons followed quickly (within 20 s) by nearly complete desensitization. The desensitization was transient since reapplication of mustard oil approximately 20 min later elicited a comparable response that also rapidly desensitized. Mustard oil also transiently cross-desensitized Vc responses to pentanoic acid (to 52%), in striking contrast to noxious heat-evoked responses which were significantly sensitized to approximately 160% of pre-mustard oil levels. The data suggest that the effect of mustard oil on subsequent lingual nociceptive responses is concentration dependent, transient, and modality specific.
Section of Neurobiology, Physiology and Behavior, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA. ctsimons@ucdavis.edu
Christopher T
CT
Simons
Satoko
S
Sudo
Makoto
M
Sudo
E
E
Carstens
D000200:Action Potentials / Q000187:drug effects / Q000528:radiation effects; D000704:Analysis of Variance; D000818:Animals; D004334:Drug Administration Schedule; D004347:Drug Interactions; D006358:Hot Temperature; D008297:Male; D009149:Mustard Plant; D009474:Neurons / Q000187:drug effects* / Q000528:radiation effects; D010421:Pentanoic Acids / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology*; D010938:Plant Oils; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014275:Trigeminal Caudal Nucleus / Q000166:cytology*
D010421:Pentanoic Acids; D010936:Plant Extracts; D010938:Plant Oils; C027793:mustard oil