Effect of D-Tubocurarine Chloride and Carbaminoylcholine on the Respiration of Daphnia

Abstract

MEASUREMENTS of the respiration of Daphnia were made by a modification of the Cartesian diver micromanometer¹. With D-tubocurarine chloride, decrease of respiration and movement begins in a concentration of 2 mgm./100 ml. At 25 mgm./100 ml. paralysis is complete and respiration diminished by 32 per cent; increasing the concentration to 150 mgm./100 ml. produces no further inhibition of respiration. Thus it appears that the diminution of respiration is due to the loss of muscular activity, which accounts for 32 per cent of the total respiration. This proportion is found to be the same in Daphnia with normal respiratory-rates ranging from 0.23 to 0.56 c.mm. oxygen/individual/hr.