Effects of TRPA1 agonists mustard oil and cinnamaldehyde on lumbar spinal wide-dynamic range neuronal responses to innocuous and noxious cutaneous stimuli in rats.
Mustard oil [allyl isothiocyanate (AITC)] and cinnamaldehyde (CA), agonists of the ion channel TRPA1 expressed in sensory neurons, elicit a burning sensation and heat hyperalgesia. We tested whether these phenomena are reflected in the responses of lumbar spinal wide-dynamic range (WDR) neurons recorded in pentobarbital-anesthetized rats. Responses to electrical and graded mechanical and noxious thermal stimulation were tested before and after cutaneous application of AITC or CA. Repetitive application of AITC initially increased the firing rate of 52% of units followed by rapid desensitization that persisted when AITC was reapplied 30 min later. Responses to noxious thermal, but not mechanical, stimuli were significantly enhanced irrespective of whether the neuron was directly activated by AITC. Windup elicited by percutaneous or sciatic nerve electrical stimulation was significantly reduced post-AITC. These results indicate that AITC produced central inhibition and peripheral sensitization of heat nociceptors. CA did not directly excite WDR neurons, and significantly enhanced responses to noxious heat while not affecting windup or responses to skin cooling or mechanical stimulation, indicating a peripheral sensitization of heat nociceptors.
Merrill
Austin W
AW
Section of Neurobiology, Physiology and Behavior, University of California, Davis, 1 Shields Ave., Davis, CA 95616, USA.
Cuellar
Jason M
JM
Judd
Justin H
JH
Carstens
Mirela Iodi
MI
Carstens
E
E
D000171:Acrolein / Q000031:analogs & derivatives* / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D017487:Ankyrins; D015220:Calcium Channels / Q000378:metabolism; D004333:Drug Administration Routes; D006930:Hyperalgesia / Q000188:drug therapy / Q000503:physiopathology*; D008161:Lumbosacral Region; D008297:Male; D009149:Mustard Plant; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D017288:Pain Threshold; D010812:Physical Stimulation / Q000379:methods; D010938:Plant Oils / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology*; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D013696:Temperature
D017487:Ankyrins; D015220:Calcium Channels; D010938:Plant Oils; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; C480976:Trpa1 protein, rat; D000171:Acrolein; C012843:cinnamaldehyde; C027793:mustard oil