title: Tricyclic antidepressant inhibition of the electrical evoked responses of the rat urinary bladder strip-effect of variation in extracellular Ca2+ concentration.
abstract: The effects of tricyclic antidepressants-amitriptyline (AMI) and desipramine (DMI)--on the rat urinary bladder strip contractility evoked by field stimulation was studied at different calcium ion (Ca2+) concentrations. In the normal Tyrode solution-(Ca2+ concentration 1.8 mM) the tricyclics reduced the electrical twitch heights. In this medium, the inhibitory effect of atropine on the twitch height was enhanced by these agents. When the Ca2+ concentration was increased 2-fold (3.6 mM) and 4-fold (7.2 mM) the effectiveness of the tricyclics was significantly reduced. When the Ca2+ concentration was reduced to one-quarter (0.45 mM) and half (0.9 mM), electrical stimulation of the strips produced contractions which were about 15% of the control twitch height in normal Tyrode solution. At these Ca2+ concentrations, the tricyclics did not produce a further reduction in twitch height. These results provide further evidence in favour of an interference with Ca2+ movement as the mechanism of the direct muscle relaxant effect of the tricyclics on the urinary bladder.
mesh_terms: D000639:Amitriptyline / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000008:administration & dosage; D002118:Calcium / Q000502:physiology*; D003891:Desipramine / Q000008:administration & dosage / Q000494:pharmacology*; D004357:Drug Synergism; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D001743:Urinary Bladder / Q000187:drug effects*
chemical_list: D000639:Amitriptyline; D001285:Atropine; D002118:Calcium; D003891:Desipramine