Actions of reactive oxygen species on AH/type 2 myenteric neurons in guinea pig distal colon.
With conventional intracellular recording methods, we investigated the mechanism of actions of reactive oxygen species (ROS) derived from hypoxanthine and xanthine oxidase (HX/XO) reactions on AH/type 2 myenteric neurons in the guinea pig distal colon. Of the 54 neurons to which HX/XO was applied, 32 neurons showed a transient membrane hyperpolarization(s) followed by a long-lasting membrane depolarization. Two additional groups of 10 myenteric neurons exhibited only a membrane hyperpolarization(s) or a late-onset membrane depolarization, respectively, and the remaining two neurons did not show any response to HX/XO. Analysis of changes of the input resistance induced by HX/XO indicated that suppression and augmentation of the conductance of Ca(2+)-dependent K(+) channels are the ionic mechanisms underlying the membrane hyperpolarization and depolarization, respectively. The effects of HX/XO on myenteric neurons were mimicked by application of caffeine or H(2)O(2). The results suggest that OH(.), but neither H(2)O(2) nor O(2)(.-), is responsible for HX/XO-induced responses. The intracellular Ca(2+) store may be the acting site of ROS in colonic AH/type 2 neurons.
Wada-Takahashi
S
S
Department of Physiology, Kanagawa Dental College, Yokosuka 238-8580, Japan.
Tamura
K
K
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D003106:Colon / Q000294:innervation*; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000378:metabolism; D019271:Hypoxanthine / Q000494:pharmacology; D008297:Male; D009197:Myenteric Plexus / Q000166:cytology* / Q000502:physiology; D009474:Neurons / Q000145:classification / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000494:pharmacology
D016877:Oxidants; D010726:Phosphodiesterase Inhibitors; D017382:Reactive Oxygen Species; D019271:Hypoxanthine; D017665:Hydroxyl Radical; D002110:Caffeine; D006861:Hydrogen Peroxide; D014969:Xanthine Oxidase