{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,11]],"date-time":"2025-11-11T12:41:15Z","timestamp":1762864875386},"reference-count":14,"publisher":"Wiley","issue":"7","license":[{"start":{"date-parts":[[2009,1,29]],"date-time":"2009-01-29T00:00:00Z","timestamp":1233187200000},"content-version":"vor","delay-in-days":2738,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["bpspubs.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["British J Pharmacology"],"published-print":{"date-parts":[[2001,8]]},"abstract":"<jats:p>\n<jats:list list-type=\"explicit-label\">\n<jats:list-item><jats:p>If one drug, B, antagonizes another, A, by producing the opposite physiological effect, the antagonist concentration\u2010effect curves should be affected by the recording system, which limits the range of agonist responses.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>With pieces of isolated guinea\u2010pig ileum taken from adjacent parts of the same animal, one recorded isotonically, the other isometrically with the same load, the isotonic IC<jats:sub>50<\/jats:sub> values for (\u2212)isoprenaline opposing carbachol or histamine were lower than the isometric values (<jats:italic>P<\/jats:italic>&lt;0.01) but there was a significant correlation between them (<jats:italic>P<\/jats:italic>&lt;0.01): the isotonic curves were steeper (<jats:italic>P<\/jats:italic>&lt;0.01) and there were wider shifts in IC<jats:sub>50<\/jats:sub> before increasing the agonist reduced the maximum relaxation.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>In similar experiments with pieces of rat uterus in oestrus from the same animal, the concentration\u2010effect curves for carbachol opposed by increasing concentrations of (\u2212)isoprenaline or (\u2212)adrenaline had slightly lower EC<jats:sub>50<\/jats:sub> values with isometric recording but there was a significant correlation (<jats:italic>P<\/jats:italic>&lt;0.01) with isotonic values. The antagonist effect (ratio of the EC<jats:sub>50<\/jats:sub> relative to that for the control) was higher with isotonic recording (<jats:italic>P<\/jats:italic>&lt;0.01 for (\u2212)isoprenaline, <jats:italic>P<\/jats:italic>&lt;0.025 for (\u2212)adrenaline) and all (27) curves were steeper than the corresponding isometric curve (<jats:italic>P<\/jats:italic>&lt;0.001).<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>The influence of the method of recording on the results is expected from the narrower operational window and smaller upper limit to relaxation with isotonic recording.<\/jats:p><\/jats:list-item>\n<jats:list-item><jats:p>A way of obtaining measurements of IC<jats:sub>50<\/jats:sub> against a standard agonist effect is suggested in an <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"#ss5\">Appendix<\/jats:ext-link>.<\/jats:p><\/jats:list-item>\n<\/jats:list>\n<\/jats:p><jats:p><jats:italic>British Journal of Pharmacology<\/jats:italic> (2001) <jats:bold>133<\/jats:bold>, 1087\u20131095; doi:<jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"doi\" xlink:href=\"10.1038\/sj.bjp.0704169\">10.1038\/sj.bjp.0704169<\/jats:ext-link><\/jats:p>","DOI":"10.1038\/sj.bjp.0704169","type":"journal-article","created":{"date-parts":[[2005,1,28]],"date-time":"2005-01-28T21:57:24Z","timestamp":1106949444000},"page":"1087-1095","update-policy":"http:\/\/dx.doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A comparison of effects measured with isotonic and isometric recording: II. 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