Reduced aversion to oral capsaicin following neurotoxic destruction of superficial medullary neurons expressing NK-1 receptors.
Aversion to capsaicin (0.1-10 ppm) was assessed using a two-bottle paired preference paradigm, before and after intracisternal injection of substance P conjugated to saporin (SP-SAP) to ablate neurons in superficial medullary and cervical dorsal horn that express NK-1 receptors. Before SP-SAP, there was a concentration-dependent decrease in consumption of capsaicin with a threshold of 0.1-0.3 ppm. Following SP-SAP, significantly more capsaicin solution was consumed at 1- and 10-ppm concentrations. These results support a role for substance P in the mediation of high, but not low, levels of capsaicin-induced oral irritation.
Department of Food Science and Technology, University of California, Davis, 1 Shields Ave., Davis, CA 95616, USA.
Christopher T
CT
Simons
Alvin G
AG
Gogineni
Mirela
M
Iodi Carstens
E
E
Carstens
D000284:Administration, Oral; D000818:Animals; D002211:Capsaicin / Q000008:administration & dosage*; D002574:Cervical Vertebrae; D007276:Injections, Intraventricular; D007509:Irritants / Q000008:administration & dosage*; D008297:Male; D008526:Medulla Oblongata / Q000473:pathology / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D010146:Pain / Q000139:chemically induced* / Q000503:physiopathology*; D017288:Pain Threshold / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000378:metabolism*; D012996:Solutions; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology
D007509:Irritants; D018040:Receptors, Neurokinin-1; D012996:Solutions; D013373:Substance P; D002211:Capsaicin