title: Neuroeffector transmission in the guinea-pig internal anal sphincter: an electrical and mechanical study.
abstract: ATP (10(-7)-10(-4) M), ADP (10(-7)-10(-4) M), AMP (10(-7)-10(-4) M) and adenosine (10(-6)-10(-4) M) each hyperpolarized the membrane, inhibited spontaneous spike discharge and relaxed the guinea-pig internal anal sphincter. All experiments were carried out using intracellular microelectrode and simultaneous tension recording techniques in the presence of phentolamine (10(-6) M) and atropine (10(-6) M). ATP was the most effective and produced a concentration-dependent membrane potential change comparable in amplitude to that produced by field stimulation of non-adrenergic non-cholinergic (NANC) nerves. Inhibitory junction potentials, the accompanying relaxations and the responses to ATP (5 X 10(-6)-5 X 10(-5) M) were additive and were increased in K+-deficient and decreased in K+-rich solutions and inhibited by apamin (10(-7) M). A proteolytic enzyme, alpha-chymotrypsin (0.5 U/ml) preferentially antagonized the ability of vasoactive intestinal polypeptide (10(-7) M) to hyperpolarize the membrane and relax the sphincter. The electrical and mechanical responses to ATP (10(-5) M) and inhibitory nerve stimulation were only slightly reduced. The results are consistent with the view that ATP or a related adenine nucleotide may have a transmitter role in the guinea-pig internal anal sphincter.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology*; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001003:Anal Canal / Q000187:drug effects*; D000818:Animals; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009469:Neuromuscular Junction / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D018377:Neurotransmitter Agents; D014660:Vasoactive Intestinal Peptide; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D011188:Potassium