Determination of Glucose Utilization Rates in Cultured Astrocytes and Neurons with [C]deoxyglucose: Progress, Pitfalls, and Discovery of Intracellular Glucose Compartmentation.

2-Deoxy-D-[C]glucose ([C]DG) is commonly used to determine local glucose utilization rates (CMR) in living brain and to estimate CMR in cultured brain cells as rates of [C]DG phosphorylation. Phosphorylation rates of [C]DG and its metabolizable fluorescent analog, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG), however, do not take into account differences in the kinetics of transport and metabolism of [C]DG or 2-NBDG and glucose in neuronal and astrocytic cells in cultures or in single cells in brain tissue, and conclusions drawn from these data may, therefore, not be correct. As a first step toward the goal of quantitative determination of CMR in astrocytes and neurons in cultures, the steady-state intracellular-to-extracellular concentration ratios (distribution spaces) for glucose and [C]DG were determined in cultured striatal neurons and astrocytes as functions of extracellular glucose concentration.

History of International Society for Cerebral Blood Flow and Metabolism.

Interest in the brain's circulation dates back more than a century and has been steadily growing. Quantitative methods for measurements of cerebral blood flow (CBF) and energy metabolism became available in the middle of the 20th century and gave a new boost to the research. Scientific meetings dealing with CBF and metabolism were arranged, and the fast growing research led to a demand for a specialized journal.

Imaging of the muscarinic acetylcholine neuroreceptor in rats with the M2 selective agonist [18F]FP-TZTP.

Introduction: [(18)F]FP-TZTP is an M2 muscarinic subtype selective receptor-binding radiotracer used in vivo to image human and nonhuman primate brain following both bolus injection and infusion. In order to carry out repeated studies in rodents, the techniques developed for primates must be transferred to rodents with the same precision. This includes obtaining a metabolite-corrected input function.

Use of [18F]fluorodeoxyglucose and the ATLAS small animal PET scanner to examine cerebral functional activation by whisker stimulation in unanesthetized rats.

Purpose: Stroking the whiskers of a rat is known to increase cerebral blood flow and glucose utilization in the somatosensory cortex. We sought to determine whether this activation could be detected with small animal PET and 2-[F]fluoro-2-deoxyglucose ([F]FDG).

Methods: Awake rats were coinjected with [F]FDG and [C]deoxyglucose ([C]DG), and during the uptake of the tracers, five, 10, or 15 whiskers on one side of the face were continuously stimulated.

The physiological and biochemical bases of functional brain imaging.

Functional brain imaging is based on the display of computer-derived images of changes in physiological and/or biochemical functions altered by activation or depression of local functional activities in the brain. This article reviews the physiological and biochemical mechanisms involved.

Operational lumped constant for FDG in normal adult male rats.

Unlabelled: We determined an operational value for the lumped constant to be used in measurements of the local rate of cerebral glucose use (lCMR(glc)) with FDG in normal adult male rats.

Methods: The standard quantitative autoradiographic method was used with 2-deoxy-d-(14)C-glucose ((14)C-DG) and with (14)C-FDG in awake normal adult male rats. Timed arterial blood samples were drawn for 45 min after the bolus and assayed for plasma glucose and (14)C concentrations.

Intranasal administration of E-selectin to induce immunological tolerization can suppress subarachnoid hemorrhage-induced vasospasm implicating immune and inflammatory mechanisms in its genesis.

Evidence that inflammatory and immune mechanisms may have a critical role in the development of vasospasm after subarachnoid hemorrhage is accumulating. We examined, therefore, whether induction of immunological tolerance to the adhesion molecule that is uniquely expressed on activated endothelium, E-selectin, could inhibit the vasospasm provoked by subarachnoid blood in a rat subarachnoid hemorrhage model. We found that intranasal instillation of E-selectin every other day for 10 days on a mucosal tolerization schedule suppressed delayed type hypersensitivity to E-selectin confirming tolerance to that molecule and markedly suppressed basilar artery spasm after subarachnoid hemorrhage.

Distribution of the 5-HT(1A) receptor antagonist [ (18)F]FPWAY in blood and brain of the rat with and without isoflurane anesthesia.

Purpose: To determine whether brain and plasma equilibrium of a proposed PET tracer for 5-HT(1A), [(18)F]FPWAY, can be achieved in a sufficiently short time for practical use of the brain to plasma equilibrium distribution ratio (DR) to monitor receptor availability with and without isoflurane anesthesia.

Methods: Awake (n=4) and isoflurane-anesthetized (n=4) rats were administered a continuous 60 min intravenous infusion of [(18)F]FPWAY with timed arterial blood sampling. Brains of the isoflurane-anesthetized rats were scanned with the ATLAS small animal PET scanner; awake rats were not.

Developmental disruption of serotonin transporter function impairs cerebral responses to whisker stimulation in mice.

There is growing evidence that serotonin (5-hydroxtryptamine, 5-HT) has major influences on brain development in mammals. Genetic and pharmacological disruption of 5-HT signaling during early postnatal development in rodents causes neuroanatomical cortical abnormalities, including malformations in the somatosensory cortex. Possible functional consequences of this developmental perturbation by 5-HT are not yet understood.

Cardiac glucose utilization in mice with mutated alpha- and beta-thyroid hormone receptors.

Abnormal thyroid function is usually associated with altered cardiac function. Mutations in the thyroid hormone (TH)-binding region of the TH beta-receptor (TRbeta) that eliminate its TH-binding ability lead to the thyroid hormone resistance syndrome (RTH) in humans, which is characterized by high blood TH levels, goiter, hyperactivity, and tachycardia. Mice with "knock-in" mutations in the TH alpha-receptor (TRalpha) or TRbeta that remove their TH-binding ability have been developed, and those with the mutated TRbeta (TRbeta(PV/PV)) appear to provide a model for RTH.

Absolute quantification of regional cerebral glucose utilization in mice by 18F-FDG small animal PET scanning and 2-14C-DG autoradiography.

Unlabelled: The purpose of this study was to evaluate the feasibility of absolute quantification of regional cerebral glucose utilization (rCMR(glc)) in mice by use of (18)F-FDG and a small animal PET scanner. rCMR(glc) determined with (18)F-FDG PET was compared with values determined simultaneously by the autoradiographic 2-(14)C-DG method. In addition, we compared the rCMR(glc) values under isoflurane, ketamine and xylazine anesthesia, and awake states.

Measurement of cerebral glucose metabolic rates in the anesthetized rat by dynamic scanning with 18F-FDG, the ATLAS small animal PET scanner, and arterial blood sampling.

Unlabelled: Rodent models and genetically altered mice have recently become available to study many human diseases. A sensitive and accurate PET scanner for small animals would be useful to evaluate treatment of these diseases in rodent models. To examine the feasibility of performing quantitative PET studies, we performed dynamic scans with arterial blood sampling in anesthetized rats with the ATLAS (Advanced Technology Laboratory Animal Scanner) small animal PET scanner developed at the National Institutes of Health and (18)F-FDG and compared activities determined by PET scanning with those obtained by direct tissue sampling.

Functional activation of cerebral metabolism in mice with mutated thyroid hormone nuclear receptors.

Neonatal hypothyroidism impairs structural maturation in the brain and results in diminished electrical activities and energy metabolism. We recently found that glucose utilization (CMR(glc)) is markedly depressed throughout the brain in mice with targeted mutations in thyroid hormone receptor alpha1 (TR alpha 1), but not TR beta. Previous studies had shown that CMR(glc) increases linearly with spike frequency in the afferent pathways to synapse-rich regions in neuropil, but not in neuronal cell bodies.

Inhibition of [18F]FP-TZTP binding by loading doses of muscarinic agonists P-TZTP or FP-TZTP in vivo is not due to agonist-induced reduction in cerebral blood flow.

[(18)F][3-(3-(3-Fluoropropyl)thio)-1,2,5-thiadiazol-4-yl]-1,2,5,6-tetrahydro-1-methylpyridine ([(18)F]FP-TZTP) is an M2 selective muscarinic agonist that may allow noninvasive studies of Alzheimer's disease with PET. 3-(3-(Propylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (P-TZTP), a nonfluorinated analog of FP-TZTP, and unlabeled FP-TZTP inhibited [(18)F]FP-TZTP binding in vivo. Because muscarinic action of the loading dose of P-TZTP administered might have had pharmacological effects, the apparent inhibition might have resulted from reduced delivery rather than competition with receptor-binding.

Dichloroacetate effects on glucose and lactate oxidation by neurons and astroglia in vitro and on glucose utilization by brain in vivo.

Neuronal cultures in vitro readily oxidized both D-[(14)C]glucose and l-[(14)C]lactate to (14)CO(2), whereas astroglial cultures oxidized both substrates sparingly and metabolized glucose predominantly to lactate and released it into the medium. [(14)C]Glucose oxidation to (14)CO(2) varied inversely with unlabeled lactate concentration in the medium, particularly in neurons, and increased progressively with decreasing lactate concentration. Adding unlabeled glucose to the medium inhibited [(14)C]lactate oxidation to (14)CO(2) only in astroglia but not in neurons, indicating a kinetic preference in neurons for oxidation of extracellular lactate over intracellular pyruvatelactate produced by glycolysis.

Functional mapping of the primate auditory system.

Cerebral auditory areas were delineated in the awake, passively listening, rhesus monkey by comparing the rates of glucose utilization in an intact hemisphere and in an acoustically isolated contralateral hemisphere of the same animal. The auditory system defined in this way occupied large portions of cerebral tissue, an extent probably second only to that of the visual system. Cortically, the activated areas included the entire superior temporal gyrus and large portions of the parietal, prefrontal, and limbic lobes.

A method for measuring cerebral glucose metabolism in vivo by 13C-NMR spectroscopy.

Current methods for estimating the rate of cerebral glucose utilization (CMR(glc)) typically measure metabolic activity for 40 min or longer subsequent to administration of [(13)C]glucose, 2-[(14)C]deoxyglucose, or 2-[(18)F]deoxyglucose. We report preliminary findings on estimating CMR(glc) for a period of 15 min by use of 2-[6-(13)C]deoxyglucose. After a 24-hr fast, rats were anesthetized, infused with [1-(13)C]glucose for 50 min, and injected with 2-[6-(13)C]deoxyglucose (500 mg/kg).

Effects of dopamine receptor blockade on cerebral blood flow response to somatosensory stimulation in the unanesthetized rat.

Local cerebral blood flow (CBF) was determined in 30 cerebral structures, including four structures of the whisker-to-barrel cortex sensory pathway, by the quantitative autoradiographic [(14)C]iodoantipyrine method during unilateral vibrissal stimulation in rats administered 0.1 or 1.0 mg/kg haloperidol or its control vehicle intravenously.

Blockade of K(ATP) channels with glibenclamide does not alter functional activation of cerebral blood flow in the unanesthetized rat.

Possible involvement of ATP-sensitive K(+) (K(ATP)) channels in the cerebral blood flow (CBF) response to neuronal functional activation was investigated in unanesthetized rats. Glibenclamide (1, 2, or 10 micromol/l), a specific inhibitor of K(ATP) channels, was infused intracisternally continuously for 30 min prior to and during the 1-min period of measurement of CBF. Unilateral functional activation was maintained throughout the measurement of CBF by continuous stroking of the vibrissae on the left side of the face.