The mechanism of the vasodilator effect of adrenaline. II. Influence of anesthetics on the depressor, pressor and lactic acid stimulating effects of adrenaline.

Abstract

Summary.The influence of different anesthetics on the depressor and pressor as well as the lactic acid stimulating effects of adrenaline were investigated in cats and compared with the corresponding effects in unanesthetized animals. Adrenaline was infused intravenously for 5 minutes in increasing doses ranging from 0.1 to 24.3 μg per kg body weight per minute.In unanesthetized animals the depressor effect was very slight, although adrenaline reduced the total peripheral resistance; this probably because the blood‐pressure regulation was better than in the anesthetized animals. In most of the latter the depressor effect emerged, but its magnitude varied considerably according to the anesthetic employed. Broadly speaking, the depressor effect showed a statistically significant correlation both to adrenaline's ability to increase the lactic acid content of the blood and to the basal blood‐pressure level.The same factors that amplified the depressor effect of adrenaline weakened its pressor effect. The latter was negatively correlated to the basal blood‐pressure level and to the lactic acid producing capacity of adrenaline. Further, the anesthetic had a direct inhibitory effect on adrenaline's vasoconstrictor action.In the individual cases the influence of the different anesthetics on adrenaline's circulatory effect was explained as follows. Ether amplified the lactic acid production and raised the basal blood pressure in relation to adrenaline's effect on unanesthetized animals, the depressor effect was very pronounced and the pressor effect greatly weakened. Urethane did not influence the lactic acid production, but elevated the basal blood pressure; the depressor effect was distinct but the pressor effect weakened. Evipan did not demonstrably influence either the lactic acid production or the basal blood pressure; the depressor effect was somewhat greater and the pressor effect somewhat less than in unanesthetized animals. Dial inhibited the lactic acid production without definitely influencing the basal blood pressure; the depressor effect was weak but the pressor effect amplified. Chlo‐ralose inhibited the lactic acid producing action of adrenaline but concurrently raised the basal blood pressure; these effects on adrenaline's action tended to counterbalance each other.Noradrenaline had neither a lactic acid stimulating nor a depressor effect on ether‐anesthetized cats.