Evidence that inhibitory neurotransmission differs between the proximal and distal segments of guinea-pig taenia caeci.
The effect of atropine (1 microM) and N(G)-nitro-L-arginine (L-NOARG, 10 microM) on electrical field stimulation induced relaxation in proximal and distal segments of guinea-pig taenia caeci in the presence of guanethidine (4 microM) was studied. The frequency-dependent relaxations were lower in proximal than in distal segments both in the presence and in the absence of atropine. The effect of L-NOARG (an inhibitor of nitric oxide (NO) synthase) on relaxation in the presence of atropine depended on the frequency of electrical stimulation and the segment used; the effect of L-NOARG was greater in proximal segments than in distal segments. In the absence of atropine, the inhibitory effect of L-NOARG was the same in both segments at all frequencies tested. This study demonstrates differences between the opposite extremes of guinea-pig taenia caeci in relaxations induced by electrical stimulation. Our data also show a role of NO that is dependent on the integrity of cholinergic transmission.
Caballero Alomar
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Unit of Pharmacology, Faculty of Medicine, University of Barcelona, Spain. catalina@medicina.ub.es
Santos
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Puig-Parellada
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D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D002432:Cecum / Q000294:innervation / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006145:Guanethidine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors* / Q000502:physiology; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000187:drug effects; D019335:Nitroarginine / Q000494:pharmacology*; D010275:Parasympathetic Nervous System / Q000502:physiology; D010276:Parasympatholytics / Q000494:pharmacology
D004791:Enzyme Inhibitors; D018377:Neurotransmitter Agents; D010276:Parasympatholytics; D019335:Nitroarginine; D009569:Nitric Oxide; D001285:Atropine; D019001:Nitric Oxide Synthase; D006145:Guanethidine