Effects of capsaicin on KCl-induced blood flow and sensory nerve activity changes in the tooth pulp.
Potassium ion-containing solutions have been shown to initially excite then depress intradental nerve activity (INA) when applied into deep dentinal cavities. The INA reflects activity originating in intradental A fibers. Application of KCl to deep dentinal cavities also induces an increase in pulpal blood flow (PBF). Capsaicin is known to exert a highly selective desensitizing effect on polymodal C-fiber nerve endings. These C fibers are generally believed to release vasoactive substances in response to stimulation. In order to determine if KCl exerts its vascular effect via activation of capsaicin-sensitive nerve fibers, we examined blood flow and sensory nerve responses to KCl obtained before and after capsaicin desensitization. The A-fiber nerve activity was determined by using INA recording technique. Blood flow was measured simultaneously from the same tooth using laser Doppler flowmetry. Local application of 0.25 M KCl to a deep dentinal cavity induced a brief spike burst and an increase in PBF of 76.0 +/- 14.6% (n = 8). Repeated applications of 0.25 M KCl caused a consistent increase in the peak PBF amplitude (n = 8). Local application of 100 microM capsaicin to a deep dentinal cavity caused an increase in PBF of 116.8 +/- 26.3% (n = 8) lasting 12-18 min, but capsaicin application did not appear to evoke any INA response. The amplitude of PBF in response to capsaicin application declined during repeated applications. Following repeated applications of capsaicin the PBF response to KCl was significantly reduced (9.9 +/- 4.3%, n = 8).(ABSTRACT TRUNCATED AT 250 WORDS)
Pertl
Christof
C
Universitäts Zahnklinik Graz, GrazAustria Department of Endodontics, School of Dental and Oral Surgery, Columbia University, New York, NYUSA Division of Research and Development, Block Drug Company, Jersey City, NJUSA Department of Endodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA.
Min-Tsai
Liu
L
Markowitz
Kenneth
K
Kim
Syngcuk
S
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D002415:Cats; D003782:Dental Pulp / Q000098:blood supply / Q000294:innervation*; D005260:Female; D017078:Laser-Doppler Flowmetry; D008297:Male; D009420:Nervous System / Q000187:drug effects; D009424:Nervous System Physiological Phenomena; D010208:Papaverine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects; D012677:Sensation / Q000502:physiology*
D011189:Potassium Chloride; D010208:Papaverine; D002211:Capsaicin