Pharmacological properties of the atropine-resistant contraction of the carp (Cyprinus carpio) intestinal bulb induced by transmural stimulation.
1. The pharmacological properties of the atropine-resistant contraction of the carp intestinal bulb induced by transmural stimulation were investigated. 2. In the presence of atropine (1 microM), transmural stimulation caused frequency-dependent (2-50 Hz) contraction which was abolished by tetrodotoxin (780 nM). 3. The atropine-resistant contraction was not decreased by tubocurarine (5 microM), hexamethonium (100 microM), carteolol (5 microM) and phentolamine (5.4 microM). 4. In vitro pretreatment with guanethidine (10 microM for 1 hr) markedly decreased the noradrenaline and adrenaline contents of the carp intestinal bulb. The atropine-resistant contraction was not affected by pretreatment with guanethidine. 5. Diphenhydramine (1 microM), methysergide (3 microM) and naloxone (1 microM) did not decrease the atropine-resistant contraction, indicating that histamine, 5-hydroxytryptamine and opioid peptides were not involved in the atropine-resistant response. 6. These results indicate that a non-cholinergic, non-adrenergic excitatory nerve is present in the carp intestinal bulb. The neurotransmitter mediating the excitatory response could not be identified.
D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D002347:Carps / Q000502:physiology*; D003530:Cyprinidae / Q000502:physiology*; D004558:Electric Stimulation; D004723:Endorphins / Q000494:pharmacology; D005260:Female; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D007422:Intestines / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D011950:Receptors, Cholinergic / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects
D004723:Endorphins; D011950:Receptors, Cholinergic; D012701:Serotonin; D009270:Naloxone; D001285:Atropine; D006632:Histamine