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The concentrations of creatine phosphate, ATP and lactate were measured in the brain and skeletal muscle of rats under halothane anesthesia (1 to 2% in oxygen) and in animals either premedicated with haloperidol or spiperone (200 mg kg-1 and 2 mg kg-1) or treated with dantrolene (860 mg kg-1). Haloperidol and spiperone had no effect on ATP or lactate in skeletal muscle, but caused more than a 30% increase in the concentration of creatine phosphate (p less than 0.01). With dantrolene, an 80% increase in creatine phosphate (p less than 0.0001) and a significant decrease in lactate (p less than 0.0001) were found. Haloperidol caused a significant decrease in brain creatine phosphate concentration (p less than 0.05) while at a dosage of 2 mg kg-1, the ATP concentration was higher (p less than 0.05). Spiperone (2 mg kg-1) caused a 19% increase in creatine phosphate (p less than 0.005) as well as a significant decrease in lactate (p less than 0.005). Dantrolene had no significant effect on the concentration of any brain metabolite. Our results indicate that the effect of anesthetics on the concentration of energy metabolites in tissues can be influenced by drug treatment, which may have implications in the choice of an anesthetic regimen to be used in tissue harvesting.

The effects of cations, temperature and tetracaine on potassium-induced contractures of rat soleus and extensor digitorus longus (e.d.l.) muscles were investigated. In the soleus, the threshold for the potassium contracture was lower (10-20 vs 20-40 mM), the peak amplitude was up to fourteen times larger, and the time course was about one half that in the e.d.l. muscle. The extent of inactivation of a test potassium contracture was directly related to the concentration of potassium in the conditioning solution and the period of exposure. Removal of calcium reduced the amplitude and time course of potassium contractures in both preparations. Addition of cobalt (10 mM) reduced the amplitude but prolonged the time course of contractures. Exposure of muscles to tetracaine (10(-5)-10(-6) M for 30 min) increased, but higher concentrations reduced, the amplitude of potassium contractures. When present for one minute, tetracaine (1 mM) moved the potassium activation curve to higher, and the potassium inactivation curve to lower, potassium concentrations.

Rats were anaesthetized with ten anaesthetics. Ketamine and enflurane gave the lowest concentration of creatine phosphate and ATP and the highest of lactate in brain, while giving the highest concentration of the high-energy phosphates and the lowest of lactate in skeletal muscle. In general, intraperitoneally-administered anaesthetics gave higher concentrations of creatine phosphate and ATP and lower concentrations of lactate in brain than did the inhalant anaesthetics. The most rapid induction of anaesthesia was achieved with halothane and enflurane, while ketamine gave variable induction times and poor analgesia. Halothane stimulated glycolysis and lowered the concentrations of high-energy phosphates in skeletal muscle.

The effects of multivalent cations, membrane potential and temperature on caffeine contractures of rat soleus and extensor digitorus longus (e.d.l.) muscles were investigated. The amplitude of the caffeine contracture was depressed by the removal of calcium and by the addition of a high concentration (1 mM) of lanthanum. Low concentrations of lanthanum (0.1-0.5 mM) augmented the caffeine contracture. Low levels of depolarization by potassium (10-40 mM) augmented the amplitude of the caffeine contracture, while higher concentrations of potassium depressed the contracture. Maximum augmentation of the caffeine contracture occurred with a higher concentration of potassium (20 mM vs 10 mM) in the e.d.l. than in the soleus muscle. The amplitude of contractures was directly related to temperature between 22 and 37 degrees C and inversely related to temperature below 22 degrees C. The effects of caffeine in rat skeletal muscle are suggested to be exerted on the sarcolemma and the mechanisms of action are by modification of the processes of activation and inactivation.