Increased responsiveness to 5-hydroxytryptamine after antigenic challenge is inhibited by nifedipine and niflumic acid in rat trachea in vitro.
Antigenic challenge often induces hyperreactivity in asthmatic airway, although the precise mechanism(s) underlying this increased responsiveness is not entirely known. Tracheae obtained from ovalbumin (OVA)-sensitized saline- or OVA-challenged rats were placed in 10 mL bath chambers for isometric recording of 5-hydroxytryptamine (5-HT)-induced contractions. 5-Hydroxytryptamine induced a stronger contraction compared with control in antigen-challenged trachea under normal or Ca2+-free conditions. In tracheae pretreated with the L-type Ca2+ channel blocker nifedipine (10(-6) mol/L) or the Ca2+-activated Cl- channel blocker niflumic acid (10(-4) mol/L), this hyperresponsiveness was not developed in either normal or Ca2+-free medium. The increased contractile response to 5-HT in allergic rat isolated trachea may be related to a greater ionic (Ca2+ and Cl-) channel involvement.
Moura
Carlos Tiago Martins
CT
Department of Physiology and Pharmacology, School of Medicine, Federal University of Ceará, Fortaleza, Brazil.
Bezerra
Fernanda Carvalho
FC
de Moraes
Isabelle Maciel
IM
Magalhães
Pedro Jorge Caldas
PJ
Capaz
Francisco Ruy
FR
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D000941:Antigens / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology*; D009544:Niflumic Acid / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D000941:Antigens; D002121:Calcium Channel Blockers; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D009544:Niflumic Acid; D009543:Nifedipine; D002118:Calcium