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PubMedDate not supplied

Is long-distance bird flight equivalent to a high-energy fast? Body composition changes in freely migrating and captive fasting great knots.

We studied changes in body composition in great knots, Calidris tenuirostris, before and after a migratory flight of 5,400 km from northwest Australia to eastern China. We also took premigratory birds into captivity and fasted them down to their equivalent arrival mass after migration to compare organ changes and nutrient use in a low-energy-turnover fast with a high-energy-turnover fast (migratory flight). Migrated birds were as economical as any fasting animal measured yet at conserving protein: their estimated relative protein contribution (RPC) to the energy used was 4.0%. Fasted birds had an estimated RPC of 6.8% and, consequently, a much lower lean mass and higher fat content for an equivalent body mass than migrated birds. Lean tissue was catabolized from most organs in both groups, except the brain. Furthermore, a principal components biplot showed that individuals were grouped primarily on the basis of overall organ fat or lean tissue content rather than by the size of specific organs. This indicates that organ changes during migratory flight are similar to those of a low-energy fast, although the length of the fast in this study probably accentuated organ reductions in some functional groups. Whether the metabolic characteristics of a flying migratory fast follow the three-phase model described in many inactive fasting animals is unclear. We have some evidence for skeletal fat being catabolized without phase 3 of a fast having been reached.

Analysis of Variance↗

PubMed2005

Fasting apoprotein B-48 level and coronary artery disease in a population without frank fasting hypertriglyceridemia.

The aim of this study was to test the hypothesis that fasting apoprotein B-48 level might be a surrogate marker of postprandial lipemia in evaluating the risk of coronary artery disease (CAD) in a population without frank abnormality in fasting lipid profile. One hundred twenty-three patients tested by coronary angiography were selected on the criteria of absence of treatment with hypolipidemic drugs, obvious hypertriglyceridemia (>2.85 mmol/L), or other conditions that may interfere with lipoprotein metabolism except diabetes. CAD was defined by more than 50% narrowing of vessel lumen, and its severity is determined by the number of arteries involved. Fasting apoprotein B-48 was measured by a competitive enzyme-linked immunosorbent assay method. There was no difference in fasting apoprotein B-48 levels between the groups with and without CAD (0.123+/-0.096 vs 0.136+/-0.125 microg/mL, respectively), whatever the sex or whether with or without diabetes. The apoprotein B-48 level was not related to the presence or the severity of CAD. There was also no correlation between fasting apoprotein B-48 levels and age, sex, body mass index, and usual fasting lipid parameters in both patients with and without angiographically proven CAD. Finally, among the features of metabolic syndrome, apoprotein B-48 was correlated with fasting triglyceride levels (r=0.357, P<.01) only. In conclusion, the present study shows that in the absence of any major fasting abnormality in plasma lipid parameters, fasting apoprotein B-48 level, which has been associated with postprandial hyperlipidemia, does not predict the risk of CAD.

Aged↗

PubMed2006

Comparison of insulin resistance and serum high-sensitivity C-reactive protein levels according to the fasting blood glucose subgroups divided by the newly recommended criteria for fasting hyperglycemia in 10059 healthy Koreans.

The increment for the prevalence of diabetes mellitus and impaired glucose tolerance warrants lowering the cutoffs of normoglycemia to help predict the future development of diabetes. The aim of this study was to find out whether insulin resistance and high-sensitivity C-reactive protein (hsCRP), a nontraditional cardiovascular risk factor, were related to the fasting glucose level, even in normoglycemic range that was categorized by the newly recommended criteria by the American Diabetes Association. Among the participants undergoing medical checkup program at Kangbuk Samsung Hospital, 10059 subjects (5535 men and 4524 women; mean age, 45 years) with normal fasting glucose levels, as defined by the newly recommended criteria (<5.6 mmol/L), were enrolled in this study. The blood pressures, body mass index (BMI), fasting blood glucose, fasting insulin, lipid batteries, and hsCRP levels were checked. The homeostatic model assessment-insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check indexes (QUICKI) were calculated. All subjects were subdivided into 4 groups according to the fasting glucose level. The HOMA-IR, QUICKI, and log-transformed (log) hsCRP, or log(hsCRP), level significantly increased according to the increment in fasting glucose, and these associations were consistent after adjustment for age and BMI, except for the log(hsCRP) (P = .124 after adjustment). Log(hsCRP) increased as the HOMA-IR increased and as the QUICKI decreased, and when multiple regression analysis was done with log(hsCRP) as the dependent variable, age, high BMI, male sex, high HOMA-IR, hypertriglyceridemia, and low high-density lipoprotein cholesterol were the significant predictor for log(hsCRP). In conclusion, the insulin resistance indexes and hsCRP increased gradually even in the normal fasting glucose range, as categorized by the newly recommended criteria for abnormal fasting glucose levels, supporting the rationale for expanding the range of fasting hyperglycemia.

Adult↗

PubMed2006

Measuring glycaemic responses: duplicate fasting samples or duplicate measures of one fasting sample?

The precision with which glycaemic responses, expressed as incremental area under the curve (AUC), can be measured may be improved by using the average of several measures of fasting blood glucose (FBG). To see if taking two fasting blood samples would increase the precision of AUC, the glycaemic responses elicited by four test meals (50 g glucose; 50 g glucose plus 10 g fat and 10 g protein; 100 g white bread; 100 g white bread plus 10 g fat and 10 g protein) were determined in thirteen overnight-fasted healthy subjects. Two fasting blood samples were taken 5 min apart (-5 min and 0 min before starting to eat) with glucose measured three times in each sample. AUC was calculated using different estimates of FBG derived from the three measures of glucose in the two fasting blood samples and each set of AUC values subjected to ANOVA. Unexpectedly, the results were more precise when AUC was calculated from mean glucose in the 0 min blood sample (FBG0) than from mean glucose in the two different fasting blood samples. The 95 % CI of the AUC calculated using FBG0 in thirteen subjects was +/-29.8; to obtain the same CI using the mean of the two fasting blood samples would require fourteen subjects. These results suggest that taking two fasting blood samples does not necessarily improve, and may even reduce, the precision of AUC as a measure of glycaemic response. Further studies are needed before requiring that two fasting blood samples be taken for determining glycaemic index.

Adult↗

PubMed1983

Ketone-glucose interaction in fed, fasted, and fasted-infected sheep.

Ketosis following starvation was suppressed by hindlimb infection in seven fasted sheep. Glucose production determined following the primed constant infusion of [6-3H(N)]glucose was elevated in the fasted-infected animals (9.50 +/- 1.11 mmol X kg-1 X min-1 (mean +/- SE) versus fasted controls (5.56 +/- 2.2). To determine if the ketonemia following sepsis contributed to the increased glucogenesis associated with catabolic disorder, glucose production and arterial substrates were measured before and after infusion of sodium-DL-beta-hydroxybutyrate (beta-OHB, 20 mumol X kg-1 X min-1) in fed, fasted, and fasted-infected animals. Following 3 h of beta-OHB infusion in the awake conditioned animals, beta-OHB and acetoacetate blood concentrations more than doubled. With infusion, blood glucose and alanine concentrations decreased in the fed and fasted sheep but not in the fasted-infected group. Glucose production fell significantly from 10.11 +/- 1.33 to 8.44 +/- 1.05 in the fed animals and from 5.05 +/- 0.28 to 4.11 +/- 0.33 in the fasted group. Glucose production was unaffected by beta-OHB infusion in the fasted-infected animals (9.50 +/- 1.83 vs. 9.11 +/- 1.44). The accelerated rate of glucose production in sheep following infection is not a consequence of the hypoketonemic state associated with sepsis.

Acidosis↗

PubMed1979

Effect of fasting and fasting and refeeding on hepatic and renal gluconeogenic enzymes in the chicken.

The effect of fasting and fasting and refeeding on hepatic and renal gluconeogenic enzyme activities were studied in six-week-old chickens (Gallus domesticus: New Hampshire male x Columbian female). Hepatic pyruvate carboxylase appeared not to be affected by fasting, but the renal enzyme activity increased in four-day fasted chickens. The hepatic mitochondrial and cytosolic phosphoenolpyruvate carboxykinases were essentially not affected by fasting. The renal mitochondrial phosphoenolpyruvate carboxykinase showed a slight increase in activity only after a four-day fast, but the cytosolic enzyme activity increased markedly already after a two-day fast. Also the activities of the hepatic and renal fructose-1,6-diphosphatase and glucose-6-phosphatase increased markedly on fasting. Refeeding for four days after a four-day fast returned these enzyme activities to near control values.

Animals↗

PubMed2001

The dietary composition of pre-fast meals and its effect on 24 hour food and water fasting.

BACKGROUND: Fasting is required by the Jewish and Islamic religions, and may sometimes be necessary for non-religious reasons as well. Very little empiric data are available on the effect of 24 hours of food and water deprivation. OBJECTIVES: To compare the effects of the dietary composition of different pre-fast meals on subjective discomfort and various other parameters of a 24 hour food and water fast. METHODS: Thirteen volunteers of both genders participated in a non-randomized crossover study. Each consumed three different equicaloric pre-fast meals in which the main source of calories was protein (49% of calories), carbohydrate (86%), or fat (69%). Weight, heart rate, blood pressure, blood and urine were tested before and after 24 hours of fasting, and the subjective evaluations of the discomfort during the three fasts were compared. RESULTS: After the protein-rich meal greater discomfort and more side effects were reported. Weight and blood pressure decreased at the end of the fasts that followed each of the three meals; heart rate increased after the high fat and carbohydrate meals but not after the protein meal. The main laboratory findings were a 40% increase in blood urea nitrogen and higher urine osmolarity after the protein-rich meal than after the other meals. CONCLUSION: A protein-poor pre-fast meal is likely to be followed by easier fasting.

Adult↗

PubMed1998

Synchronous firing of inhibitory interneurons results in saturation of fast GABA(A) IPSC magnitude but not saturation of fast inhibitory efficacy in rat neocortical pyramidal cells.

The kinetic properties of evoked fast inhibitory postsynaptic currents were examined to elucidate factors underlying the limit on the magnitude of fast inhibition in neocortex. Using whole-cell voltage-clamp recordings from layer V pyramidal neurons in slices of rat somatosensory cortex, fast gamma-aminobutyric acid-A (GABA[A])ergic inhibitory postsynaptic currents were selectively recorded by holding cells at potentials equal to excitatory postsynaptic current reversal (approximately 0 mV). As stimulus intensity was increased, the magnitude and duration of the fast inhibitory postsynaptic current increased. Over the range of stimuli applied (2-10 V), fast GABA(A)-mediated inhibitory postsynaptic currents reached a maximum peak conductance of 25.9 +/- 4.2 nS (range 10.5-41.2 nS) at intensities approximately 2-times threshold. As stimulus intensities were increased beyond this point of maximal conductance, the time constant of current decay increased as function of stimulus strength, while rise time remained unaffected. Exposure to nominally magnesium-free solutions did not affect maximal peak conductances of fast inhibitory postsynaptic currents, but did cause an increase in the time constants of current decay by 66.3 +/- 23.6%, resulting in an 85.6 +/- 24.6% increase in the total charge flux carried by single inhibitory postsynaptic currents. This effect may be due to prolonged activation of postsynaptic GABA(A) receptors by excess GABA released in response to increased excitation. Exposure to the GABA uptake blocker, nipecotic acid, similarly prolonged current decay without affecting the maximal peak conductance. Our findings suggest that the limit on recruitment of evoked fast inhibition in neocortical layer V pyramidal cells arises from the saturation of postsynaptic GABA(A) receptors. However, while there is a limit to the peak fast inhibitory postsynaptic conductance which can be recruited with increasing excitation, inhibitory strength may still be modulated by increasing charge flux through the prolongation of fast inhibition.

Animals↗

PubMed1997

Fast fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging of the brain: a comparison of multi-shot echo-planar and fast spin-echo techniques.

PURPOSE: To evaluate fast spin-echo and multi-shot echo-planar fluid-attenuated inversion recovery (FLAIR) sequences in paediatric brain imaging. MATERIALS AND METHODS: Matched images from 32 patients with suspected tumour or white matter disease were independently evaluated by two paediatric neuroradiologists. The observer preferences for image quality and lesion detection were analysed for differences between fast spin-echo FLAIR and multi-shot echo-planar FLAIR. Diagnostic quality was compared with that of fast spin-echo T2-weighted images. RESULTS: Images of a diagnostic quality equivalent to that of fast spin-echo T2-weighted images were achieved with both FLAIR techniques. Grey and white matter differentiation and cerebrospinal fluid (CSF) nulling were significantly better on fast spin-echo FLAIR sequences. CSF flow artefact was reduced on multi-shot echo-planar FLAIR. There was no difference in lesion detection. Fast spin-echo FLAIR images were visually preferred at the expense of longer imaging time. CONCLUSION: Fast FLAIR techniques are complementary to fast spin-echo T2-weighted sequences in imaging of the paediatric brain. We find that the fast spin-echo FLAIR sequence is preferable to the multi-shot echo-planar technique.

Brain↗

PubMed2006

Marketing fast food: impact of fast food restaurants in children's hospitals.

OBJECTIVES: The objectives of this study were (1) to determine fast food restaurant prevalence in hospitals with pediatric residencies and (2) to evaluate how hospital environment affects purchase and perception of fast food. METHODS: We first surveyed pediatric residency programs regarding fast food restaurants in their hospitals to determine the prevalence of fast food restaurants in these hospitals. We then surveyed adults with children after pediatric outpatient visits at 3 hospitals: hospital M with an on-site McDonald's restaurant, hospital R without McDonald's on site but with McDonald's branding, and hospital X with neither on-site McDonald's nor branding. We sought to determine attitudes toward, consumption of, and influences on purchase of fast food and McDonald's food. RESULTS: Fifty-nine of 200 hospitals with pediatric residencies had fast food restaurants. A total of 386 outpatient surveys were analyzed. Fast food consumption on the survey day was most common among hospital M respondents (56%; hospital R: 29%; hospital X: 33%), as was the purchase of McDonald's food (hospital M: 53%; hospital R: 14%; hospital X: 22%). McDonald's accounted for 95% of fast food consumed by hospital M respondents, and 83% of them bought their food at the on-site McDonald's. Using logistic regression analysis, hospital M respondents were 4 times more likely than respondents at the other hospitals to have purchased McDonald's food on the survey day. Visitors to hospitals M and R were more likely than those at hospital X to believe that McDonald's supported the hospital financially. Respondents at hospital M rated McDonald's food healthier than did respondents at the other hospitals. CONCLUSIONS: Fast food restaurants are fairly common in hospitals that sponsor pediatric residency programs. A McDonald's restaurant in a children's hospital was associated with significantly increased purchase of McDonald's food by outpatients, belief that the McDonald's Corporation supported the hospital financially, and higher rating of the healthiness of McDonald's food.

Food-Processing Industry↗

PubMed1998

T2-weighted MR imaging of the uterus: comparison of optimized fast spin-echo and HASTE sequences with conventional fast spin-echo sequences.

OBJECTIVE: Our objective was to compare the value of a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence with optimized fast spin-echo and conventional fast spin-echo techniques in evaluation of the uterus. SUBJECTS AND METHODS: Optimized fast spin-echo imaging was compared with fast spin-echo and HASTE imaging, for both image quality and ability to assess the zonal anatomy of the uterus, in 40 volunteers. In optimized fast spin-echo imaging, the imaging time was reduced using partial-Fourier reconstruction, reducing the echo spacing, and increasing the echo train length. RESULTS: HASTE imaging offered the least motion artifact of all techniques. On optimized fast spin-echo imaging, motion artifacts were moderate to severe in 10% of patients. On fast spin-echo imaging, motion artifacts were moderate to severe in 40% of patients. Optimized fast spin-echo imaging was superior to the other two techniques in terms of anatomic sharpness and overall image quality. CONCLUSION: Although HASTE imaging offers the unique feature of providing images free of motion artifacts, optimized fast spin-echo imaging appears to be the preferred technique for T2-weighted imaging of the uterus.

Adolescent↗

PubMedDate not supplied

Fast fluid-attenuated inversion recovery (FAST-FLAIR) of ischemic lesions in the brain: comparison with T2-weighted turbo SE.

PURPOSE: We compared fast fluid-attenuated inversion recovery (FAST-FLAIR) images with Turbo SE T2-weighted images to evaluate the detectability of small ischemic lesions in the brain. MATERIALS AND METHODS: Thirty-six cases of multiple cerebral ischemic lesions were examined with FAST-FLAIR and Turbo SE imaging. The detectability of lesions, ability to discriminate lesions from the cortex, visualization of perivascular space, and visualization of brainstem lesions were compared between the two sequences. RESULTS: The total number of lesions detected on both sequences was 534 in 36 cases. Six lesions in three cases were detected only on FAST-FLAIR, and one lesion in one case was detected only on the Turbo SE. All the 52 lesions located close to the cortex could be discriminated from the cortex on the FAST-FLAIR images, while 23 of these lesions could not be discriminated on the Turbo SE. Perivascular spaces were not visualized as areas of high signal on the FAST-FLAIR images. Pontine lesions that were visualized in four cases were clearer on the Turbo SE images than on the FAST-FLAIR images. CONCLUSION: The FAST-FLAIR images were shown to be useful in the detection of ischemic lesions and in distinguishing them from the surrounding normal structures. The FAST-FLAIR sequence is expected to become a new additional routine sequence.

Aged↗

PubMed2003

A preliminary fast may potentiate response to a subsequent low-salt, low-fat vegan diet in the management of hypertension - fasting as a strategy for breaking metabolic vicious cycles.

Although a salted diet appears to be a sine qua non for the development of essential hypertension, low-salt diets often have a modest or even negligible impact on the blood pressure of hypertensives; this suggests that salt, perhaps often acting in concert with other aspects of a modern, rich diet, may set in place certain metabolic vicious cycles that sustain blood pressure elevation even when dietary salt is eliminated. Therapeutic fasting is known to lower elevated blood pressure - presumably in large part because it minimizes insulin secretion - and may have the potential to break some of these vicious cycles. Goldhamer has recently reported that a regimen comprised of a water-only fast of moderate duration, followed by a transition to a low-fat, low-salt, whole-food vegan diet, achieves dramatic reductions in the blood pressure of hypertensives, such that the large majority of patients can be restored to normotensive status, in the absence of any drug therapy. Although long-term follow-up of these subjects has been sporadic, the available data suggest that these large reductions is blood pressure can be conserved in patients who remain compliant with the follow-up diet - in other words, a 'cure' for hypertension may be feasible. If a protein-sparing modified fast can be shown to be virtually as effective as a total fast for achieving these benefits, it may be possible to implement this regimen safely on an outpatient basis. The ability of therapeutic fasts to break metabolic vicious cycles may also contribute to the efficacy of fasting in the treatment of type 2 diabetes and autoimmune disorders. As a general principle, if a metabolic disorder is susceptible to prevention - but not reversal - by a specific diet, and therapeutic fasting has a temporary favorable impact on this disorder, then a more definitive therapy may consist of a therapeutic fast, followed up by the protective diet as a maintenance regimen.

Diet, Vegetarian↗

PubMed1975

Adaptation to fasting in baboon. II. Regulation of lipolysis early and late in fasting.

Regulation of lipolysis by the sympathetic nervous system, basal insulin, and glucagon was studied in fasted baboons. Beta-Adrenergic mechanisms were evaluated by blockade with propranolol after 24, 40, and 65 h of fasting. Inhibition of lipolysis decreased with increasing duration of fasting. Insulin concentrations were markedly reduced by propranolol at all stages of fasting, whereas glucose and glucagon concentrations were unchanged. The roles of insulin and glucagon were evaluated by a 2-h infusion of somatostatin after 18 and 65 h of fasting. At both times, insulin and glucagon concentrations were markedly reduced. At 18 h of fasting but not at 65 h, lipolysis doubled. At both times the plasma glucose concentration fell 15-30%. At 18 h, preventing the decrease in glucose with glucose infusion prevented the increase in lipolysis. These data suggest that a beta-adrenergic mechanism is largely responsible for regulation of lipolysis early in fasting and that insulin, glucagon, and beta-adrenergic mechanisms play no major part in the maintenance of the accelerated lipolysis later in fasting.

Animals↗

PubMed1972

Glucose-induced alkalosis in fasting subjects. Relationship to renal bicarbonate reabsorption during fasting and refeeding.

This study documents the development of alkalosis in patients returning to caloric intake after a period of starvation and investigates the mechanisms responsible for this metabolic alteration. We studied the acid-base status, bicarbonate reabsorption, acid excretion, and sodium metabolism during fasting and glucose refeeding in 19 patients receiving sodium supplements. Metabolic alkalosis developed promptly in all of the subjects who terminated an 18 day fast with 300 g of glucose daily for 4 days. Tubular maximum reabsorptive capacity for bicarbonate and renal bicarbonate threshold determinations were performed at varying intervals in six and seven subjects, respectively, who had fasted for 3-18 days. The results demonstrated that bicarbonate reabsorptive capacity was normal or low during early fasting, markedly elevated during the 2nd wk; and moderately elevated during the 3rd wk of fasting. Glucose administration at all stages of fasting caused a further increase in bicarbonate threshold. Sodium balance during fasting with sodium supplements was found to follow a triphasic pattern, with the occurrence of a natriuresis during the 1st wk followed by a period of sodium retention after which neutral daily sodium balance was reestablished. Correlation of bicarbonate reabsorption with sodium homeostasis indicated a slight decrease in renal bicarbonate threshold during the natriuretic phase, a marked increase in bicarbonate reabsorption during the period of sodium retention, and a continued moderate elevation of threshold after sodium balance was reestablished. This relationship was interpreted to indicate that changes in bicarbonate reabsorption during fasting and refeeding may be secondary to alterations in the renal reabsorption of sodium.

Absorption↗

PubMed2002

Sero-epidemiological assessment and diagnosis of visceral leishmaniasis in an endemic locality using Fast Agglutination Screening Test (FAST).

The Fast Agglutination Screening Test (FAST) was employed on sera obtained from an endemic area of visceral leishmaniasis in southwestern Ethiopia, in February 2000. The study involved (i) active case detection among 1575 residents of two villages; and (ii) passive case detection in an outpatient clinic. Sera of 1587 individuals, including 143 sera of previously treated VL patients, were tested. Based on the size of agglutination mat, the FAST results were read qualitatively as non-reactive (-), weakly reactive (1+), moderately reactive (2+) and highly reactive (3+). All FAST reactive sera were re-tested with the Direct Agglutination Test (DAT). After clinical screening of 1625 individuals, 61 individuals with signs and symptoms of early or late VL were found; 26 sera were FAST positive. Twenty-two of these suspected VL cases were subjected to parasitological examination using lymph node aspirates. Eighteen (81.8%) were confirmed either by demonstration of amastigotes in smears or promastigotes in NNN cultures. FAST reactive anti-leishmanial antibodies were detected in 4.5% of untreated and 70.6% of previously treated patients. Forty-five sera of 1390 previously untreated asymptomatic individuals (3.2%) were found to be FAST positive. This report demonstrates that FAST is a rapid and cost-effective screening test for the diagnosis and sero-epidemiological surveillance of visceral leishmaniasis.

Adolescent↗

PubMed2002

Development of a fast agglutination screening test (FAST) for the detection of anti-Leishmania antibodies in dogs.

A fast agglutination screening test (FAST) for the detection of anti-Leishmania antibodies in serum samples from dogs with visceral leishmaniosis was developed. The test is based on the direct agglutination test (DAT), but combines a higher parasite concentration with a smaller test volume. In contrast to the DAT, the FAST makes use of only one serum dilution and the results can be read within 3 h as opposed to 18-20 h for the DAT. The FAST was evaluated using serum samples of confirmed cases of the disease and healthy controls collected in the most important endemic regions of canine visceral leishmaniosis, import cases of canine leishmaniosis in a non-endemic country, from non-endemic healthy controls and from dogs with other diseases. The performance of the FAST was compared with standard DAT. In the present study, the FAST had a sensitivity of 93.6% and a specificity of 89.0%. The DAT had a sensitivity of 88.6% and a specificity of 96.7%. Furthermore, using a large panel of serum samples of previously examined DAT positive or negative dogs it was shown that degree of agreement between the two tests was high (95.7%; kappa value = 0.91). The FAST offers the advantages of the DAT based on freeze-dried antigen with respect to stability of the antigen, sensitivity and specificity. Moreover, the FAST allows the rapid screening of a large number of samples, which makes the test very useful for epidemiological screening of large populations of dogs.

Agglutination Tests↗

PubMed1998

Spike-wave complexes and fast components of cortically generated seizures. IV. Paroxysmal fast runs in cortical and thalamic neurons.

In the preceding papers of this series, we have analyzed the cellular patterns and synchronization of neocortical seizures occurring spontaneously or induced by electrical stimulation or cortical infusion of bicuculline under a variety of experimental conditions, including natural states of vigilance in behaving animals and acute preparations under different anesthetics. The seizures consisted of two distinct components: spike-wave (SW) or polyspike-wave (PSW) at 2-3 Hz and fast runs at 10-15 Hz. Because the thalamus is an input source and target of cortical neurons, we investigated here the seizure behavior of thalamic reticular (RE) and thalamocortical (TC) neurons, two major cellular classes that have often been implicated in the generation of paroxysmal episodes. We performed single and dual simultaneous intracellular recordings, in conjunction with multisite field potential and extracellular unit recordings, from neocortical areas and RE and/or dorsal thalamic nuclei under ketamine-xylazine and barbiturate anesthesia. Both components of seizures were analyzed, but emphasis was placed on the fast runs because of their recent investigation at the cellular level. 1) The fast runs occurred at slightly different frequencies and, therefore, were asynchronous in various cortical neuronal pools. Consequently, dorsal thalamic nuclei, although receiving convergent inputs from different neocortical areas involved in seizure, did not express strongly synchronized fast runs. 2) Both RE and TC cells were hyperpolarized during seizure episodes with SW/PSW complexes and relatively depolarized during the fast runs. As known, hyperpolarization of thalamic neurons deinactivates a low-threshold conductance that generates high-frequency spike bursts. Accordingly, RE neurons discharged prolonged high-frequency spike bursts in close time relation with the spiky component of cortical SW/PSW complexes, whereas they fired single action potentials, spike doublets, or triplets during the fast runs. In TC cells, the cortical fast runs were reflected as excitatory postsynaptic potentials appearing after short latencies that were compatible with monosynaptic activation through corticothalamic pathways. 3) The above data suggested the cortical origin of these seizures. To further test this hypothesis, we performed experiments on completely isolated cortical slabs from suprasylvian areas 5 or 7 and demonstrated that electrical stimulation within the slab induces seizures with fast runs and SW/PSW complexes, virtually identical to those elicited in intact-brain animals. The conclusion of all papers in this series is that complex seizure patterns, resembling those described at the electroencephalogram level in different forms of clinical seizures with SW/PSW complexes and, particularly, in the Lennox-Gastaut syndrome of humans, are generated in neocortex. Thalamic neurons reflect cortical events as a function of membrane potential in RE/TC cells and degree of synchronization in cortical neuronal networks.

Adrenergic alpha-Agonists↗