title: Capsaicin and nicotine both activate a subset of rat trigeminal ganglion neurons.
abstract: Nicotine and capsaicin produce many similar physiological responses that include pain, irritation, and vasodilation. To determine whether neuronal nicotine acetylcholine receptors (nAChR) are present on capsaicin-sensitive neurons, whole cell patch-clamp recordings were performed on rat trigeminal ganglion cells. It was found that approximately 20% of the total number of neurons tested was activated by both 100 microM nicotine and 1 nM capsaicin. Other subsets of neurons were activated by only one of these compounds, whereas a fourth subset was not activated by either compound. At -60 mV, the magnitude of the capsaicin-activated currents was about three times larger than the magnitude of the nicotine-activated currents. The current-voltage relationship of the nAChR exhibited marked rectification, such that for voltages > or = 0 mV the current was essentially zero. In contrast, the current-voltage relationship of the capsaicin-activated current was ohmic from +/- 60 mV. These data indicate the existence of subsets of capsaicin-sensitive afferent neurons.
authors.affiliation: Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: S A
authors.initials: SA
authors.lastname: Simon
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology*; D004553:Electric Conductivity; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000187:drug effects; D012430:Ruthenium Red / Q000494:pharmacology; D012964:Sodium / Q000502:physiology; D013618:Tachyphylaxis; D012668:Trigeminal Ganglion / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
chemical_list: D011978:Receptors, Nicotinic; D012430:Ruthenium Red; D009538:Nicotine; D012964:Sodium; D002211:Capsaicin; D002118:Calcium