Female Sprague-Dawley rats were chronically implanted with nuclear magnetic resonance (NMR) surface coils tuned to both 31P and 1H NMR frequencies. Alternated 31P and 1H NMR spectra were recorded at 2.5 min intervals in waking rats or rats under pentobarbital or chloral hydrate anesthesia. After a reference period, the metabolic changes were observed following intraperitoneal injection of potassium cyanide (KCN, 5 mg/kg). Among previously observed changes typical of cellular anoxia, attention was specifically paid to the relationship between the intracellular pH values and the lactate levels. The results show a strong lactate-pH correlation in waking rats, a partial decoupling under nembutal anesthesia and a complete decoupling under chloral hydrate anesthesia.