. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ACETYLCHOLINE ACTION ON VENUS HEART 83 2. Effect of temperature on the response to acetylcholine. Some of the concentration-action curves were obtained in February, others as late as May. During February the concentrations of acetylcholine which produced a just measurable inhibition on different hearts were between 5 X 10~12 (1 : 5,000,000,000,000) and 5 X lO"11. During May thresholds were found as high as 5 X 10~10. This was at first thought to be evidence of a seasonal varia- tion in sensitivity, although Prosser (194
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ACETYLCHOLINE ACTION ON VENUS HEART 83 2. Effect of temperature on the response to acetylcholine. Some of the concentration-action curves were obtained in February, others as late as May. During February the concentrations of acetylcholine which produced a just measurable inhibition on different hearts were between 5 X 10~12 (1 : 5,000,000,000,000) and 5 X lO"11. During May thresholds were found as high as 5 X 10~10. This was at first thought to be evidence of a seasonal varia- tion in sensitivity, although Prosser (1940) reported the highest sensitivity to 100 - CD X z LJ o ac ui 20 - 5X10 10 5X10 CONC. ACH. 10 5X10 FIGURE 3. Data from a typical heart showing the decrease in amplitude (per cent inhibition) as a function of the concentration of acetylcholine (ACh). occur in the spring. The experiments done thus far has been at room tempera- ture and there was some evidence that the sensitivity of a heart was lower when the room temperature was abnormally high. Therefore a few experiments were performed to determine the effect of temperature on the response of the heart to acetylcholine. By means of a bath, with temperature control, the chamber containing the heart, and the perfusion fluid, could be maintained at any tem- perature between 5° and 35° C. The range over which hearts were observed to beat satisfactorily was somewhat less than this. Beginning in some cases at a low temperature and in others at a high, the concentration of acetylcholine was found which would produce a 50 per cent decrease in amplitude. The tempera- ture was then increased or decreased and after a period of adaptation the con- centration of acetylcholine necessary for 50 per cent inhibition was again de-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the orig
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
