Inhibitory effect of caffeine on C-fibre-evoked excitation in the rat spinal dorsal horn recorded under Ca2+-free condition: an interaction with halothane.
Effect of caffeine on C-fibre-evoked excitation in the superficial dorsal horn of rat spinal cord slices was investigated in Ca(2+)-free medium using the optical imaging technique. Perfusing slices with Ca(2+)-free solution reversibly suppressed the late phase of dorsal-root stimulus-induced excitation, leaving short-lasting optical responses that primarily represent the excitation of presynaptic elements. Under the Ca(2+)-free condition, 0.1-10 mM caffeine depressed the peak optical amplitude in a concentration-dependent and reversible manner (IC(50) 4.5 mM, I(max) 84%). The volatile anaesthetic halothane at a clinical concentration (0.6 mM) also depressed the peak optical amplitude. Pretreatment with caffeine augmented the inhibitory effect of halothane. These results suggest that caffeine and halothane may interact presynaptically to cause synergistic inhibition of C-fibre-induced excitation in the dorsal horn.
Kusudo
Kei
K
Department of Human and Artificial Intelligence Systems, Fukui University, 3-9-1 Bunkyo, Fukui 910-8507, Japan.
Asai
Tatsuya
T
Ikeda
Hiroshi
H
Takenoshita
Makoto
M
Murase
Kazuyuki
K
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000344:Afferent Pathways / Q000187:drug effects; D000704:Analysis of Variance; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000172:deficiency; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D020671:Posterior Horn Cells / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
D018685:Anesthetics, Inhalation; D000697:Central Nervous System Stimulants; D002110:Caffeine; D002118:Calcium; D006221:Halothane