We determined cerebral intracellular pH in living rabbits and rats under physiologic conditions, using phosphorus NMR spectroscopy and new titration curves thought to be appropriate for brain. Mean values for the two species were, respectively, 7.14 +/- 0.04 (SD) and 7.13 +/- 0.03. These are toward the alkaline end of the range of values obtained by other methods, as values reported by other NMR workers also tend to be.

1H NMR spectra at 360.13 MHz were obtained of the rat brain in vivo by using a surface coil placed over the skull. Resonances of numerous metabolites were identified by comparison with the 1H NMR spectra of excised rat brain tissue and acid extracts of the tissue. Changes in cerebral lactate levels resulting from the administration of gas mixtures low in oxygen were monitored in the in vivo brain spectra with a time resolution of 2.3 min. The electroencephalogram and electrocardiogram were recorded simultaneously during the NMR experiment. Reversibility of the hypoxic response was documented when, upon oxygen administration, cerebral lactate returned to its prehypoxic level. These experiments demonstrate the applicability of high-resolution 1H NMR to monitor pathophysiology of brain metabolism in real time.Nuclear magnetic resonance spectroscopy (NMR) is rapidly developing into a major tool for the study of metabolism in vivo. Both 31p and 13C NMR have been used extensively in metabolic studies of cellular suspensions and perfused organs (1, 2). The recent introduction of surface coils (3) has led to the successful application of topical 31P NMR to studies of the vital organs of animals and man (4-6). Recently, topical 13C NMR has been shown to be capable of monitoring glycogen stores and acyl glycerides in vivo (7-9), greatly extending the kinds of metabolic information that can be obtained. MATERIALS AND METHODS Animal Preparation for in Vivo 1H Experiments. Rats of theCharles River strain (220-240 g), fed ad lib, were anesthetized with halothane (1%), tracheotomized, mechanically ventilated (25% 02/75% N20), and paralyzed with D-tubocurarine chloride (1.5 mg/kg, subcutaneously) and pancuronium bromide (1 mg/kg, subcutaneously). The animals were equipped with electrocardiogram leads on the left extremities and scalp leads for electroencephalogram recording. An incision was made along the midline of the calvarium so that skin and temporalis muscles-detached from the temporal ridge-could be retracted and fixed in position away from the skull. The rat was mounted vertically in a Plexiglass retainer and a small surface coil was centered 6 mm occipital to the bregma. These precautions ensure that only the contents of the skull are observed.Extract Preparation for 1H NMR. Extracts were prepared from rat brain frozen in situ (18) in the following manner: frozen cortical tissue was chipped away (68 mg) and extracted with 99% MeOH/0. 1 M HCl (2:1, wt/vol) and 0.1 M perchloric acid (10:1, wt/vol) according to well-established methods (19) with minor modifications. In the extraction procedure, 0.1 M sodium phosphate (pH 7.2) was substituted for imidazole buffer (19). After neutralization with 1.5 M KOH/0.3 M KCI the sample was lyophilized and dissolved in 0.38 ml of a 0.1 M phosphate/2H20 buffer (pH 7.2) and placed in a 5-mm NMR tube for analysis.Chemical shifts for resonances in excised and in vivo brain tissue were referenced to N-acetylaspartate at 2.023 ppm relative to sodium 3-trimethylsilyl[2,2,3,3-2H]pro...

We have used (13C)-1H NMR spectroscopy at 360.13 MHz to resolve the 13C coupled proton resonance of glutamate and lactate in the rat brain in vivo. The time required for the 13C fractional enrichment of the 4-CH2 position of brain glutamate to reach isotopic steady state was determined during a continuous infusion of D-[1-13C]glucose. Under conditions of ischemia, measurements made of the 3-CH3 of lactate in (13C)-1H NMR spectra revealed the relative contribution of brain glucose and glycogen to lactate formation. (13C)-1H NMR was 11 times more sensitive than 13C NMR for the detection of 13C in the 3-CH3 position of lactate and 6 times more sensitive for the detection of 13C in the 4-CH2 of glutamate under similar in vivo conditions.

Background-Neuroimaging and electrophysiological studies have consistently provided evidence of impairment in anterior cingulate cortex (ACC)/medial frontal cortex (MFC) function in people with schizophrenia. In this study, we sought to clarify the nature of this abnormality by combining proton magnetic resonance spectroscopy ( 1 H-MRS) with functional magnetic resonance imaging (fMRI) at 3T.

No abstract