The effect of narcotics on the endogenous respiration and succinate oxidation in oyster muscle.

The adductor muscles of Lamellibranchs present unusual features in their physiology.Thus it has been known for some time (Marceau, 19°9) that they are able to support relativelylarge tensions, and the morphologicaldifferentiation into nacreous and vitreous parts in some specieshas led various workers (Pamas, 1910; Boyland, 1928; and Kobayashi, 1929) to attempt to correlate differences in metabolism with these properties. Also, Riesser (1933) has investigated, by the usual pharmacologicaltechniques, the action of a number of compounds on invertebrate muscle, and concluded that these smooth muscles behaved similarly to cross-striated frog muscle. More recently, some features of the glycolytic mechanism (Humphrey, 1943) and of the succinoxidase system (Humphrey, 1947) in the adductor muscles of Saxostrea commercialishave been established. It was shown that succinic acid was able to increase the oxygen consumption considerably, and the effects of various inhibitors on the oxygen uptake in the presence and absence of succinic acid were determined. In continuation of this, it was thought desirable to determine the effectsof other classesof inhibitors on the oxygenconsumption, and, with this object in view, the action of narcotics was studied. The effect of narcotics on the oxidation of succinic acid was also determined, since succinic acid plays such a central role in tissue metabolism (Szent-Gyorgyi, 1937). Also, Quastel & Wheatley (1933)have found that, in general, the oxidation of succinic acid by brain tissue is, unlike the oxidation of numerous other substrates, insensitive to the presence of narcotics; it therefore becomes important to determine if such insensitivity occurs with the muscle taken from Saxostrea.