Temperature and potency of d-tubocurarine and pancuronium in vitro.
The concentrations of d-tubocurarine and pancuronium producing 50% block of the indirectly elicited twitch were determined in isolated mouse nerve-diaphragm preparations at 37 and 25 C. The contralateral side was used as a control in a 2 x 2 factorial analysis of variance. Cooling shifted the dose-response curves for both drugs to the left, but only slightly (from 1.69 +/- 0.022 microM to 1.49 +/- 0.021 microM with d-tubocurarine and from 0.65 +/- 0.012 microM to 0.46 +/- 0.009 microM with pancuronium). The dose-response relationship was, however, so steep (Hill coefficient approximately 5 to 6) that a slight horizontal shift of the dose-response curve corresponds to a considerable decrease in the twitch response at a concentration midway between the curves. Thus, studies using only the concentration that produces partial block of twitch responses misleadingly suggest a large effect of temperature. Similarly, if in another system the curve were to shift to the right even only slightly, a temperature effect in the reverse direction might be reported. It is concluded that temperature appears to have little influence on cellular potency of neuromuscular blocking agents.
D000818:Animals; D003964:Diaphragm / Q000187:drug effects / Q000294:innervation; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects*; D010197:Pancuronium / Q000494:pharmacology*; D010791:Phrenic Nerve; D013696:Temperature; D014403:Tubocurarine / Q000494:pharmacology*
D010197:Pancuronium; D014403:Tubocurarine