Abstract
It is well known that various narcotics and anesthetics have a depressing effect upon respiration but this has not been systematically investigated as a function of temperature. Thus, while something is known of the influence of this class of drugs on the absolute respiratory rate, little information is available for changes in the relative respiratory rate.
The newt, Triturus viridescens. was used in the present experiments both because it is a poikilothermous animal and therefore useful for temperature analyses and because its respiration has already been investigated by means of a Warburg apparatus suitably modified for this purpose.
The minimum dose required to maintain newts immobile for 24 hours under the conditions of temperature variations was determined experimentally for two suitable drugs. After preliminary anesthesia for 15 minutes in a 1-10 dilution of a saturated aqueous solution of chloretone, animals were transferred to modified Warburg vessels containing 1 cc of a 1-20 dilution of a saturated solution of chloretone. Comparable fluid was introduced into one unit serving as a thermobarometer. Nembutal (sodium pentobarbital) produced the desired effect with an intraperitoneal injection of 0.2 cc of a 0.6% solution.
Thermal adaptation and the procedure for measuring oxygen consumption followed that described by Pomerat and Zarrow. 1
All data reported were based on animals which remained immobile during the entire period of measurement and which recovered from the anesthetic at its conclusion.
Arrhenius plots of the data for oxygen consumption during chloretone anesthesia yielded a temperature characteristic (μ) of 17,200± (Fig. 1). This is the same value as that found for unan-esthetized animals by Pomerat and Zarrow 1 and for newts studied in relation to their endocrine system by Pomerat. 2 A similar treatment of the values obtained for 10 different animals under nembutal anesthesia is represented in Fig. 2. A distinct shift in the μ. is seen to have occurred.
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