Neuroimaging revealed long-lasting glucose metabolism changes to morphine withdrawal in rats pretreated with the cannabinoid agonist CP-55,940 during periadolescence.

This study evaluates the long-term effects of a six and 14-week morphine withdrawal in rats pretreated with a cannabinoid agonist (CP-55,940, CP) during periadolescence. Wistar rats (33 males; 32 females) were treated with CP or its vehicle (VH) from postnatal day (PND) 28-38. At PND100, rats performed morphine self-administration (MSA, 15d/12 h/session). Eight groups were defined according to pretreatment (CP), treatment (morphine), and sex. Three [18F]FDG-PET brain images were acquired: after MSA, and after six and 14 weeks of withdrawal. PET data were analyzed with SPM12. Endocannabinoid (EC) markers were evaluated in frozen brain tissue at endpoint. Females showed a higher mean number of self-injections than males. A main Sex effect on global brain metabolism was found. FDG uptake in males was discrete, whereas females showed greater brain metabolism changes mainly in areas of the limbic system after morphine treatment. Moreover, the morphine-induced metabolic pattern in females was exacerbated when CP was previously present. In addition, the CP-Saline male group showed reduced CB1R, MAGL expression, and NAPE/FAAH ratio compared to the control group, and morphine was able to reverse CB1R and MAGL expression almost to control levels. In conclusion, females showed greater and longer-lasting metabolic changes after morphine withdrawal than males, indicating a higher vulnerability and a different sensitivity to morphine in subjects pre-exposed to CP. In contrast, males primarily showed changes in EC markers. Together, our results suggest that CP pre-exposure contributes to the modulation of brain metabolism and EC systems in a sex-dependent manner.

Sustained escitalopram administration affects glucose metabolism in the rat brain.

Escitalopram is a selective serotonin reuptake inhibitor (SSRIs) antidepressant, drug that is currently used as first-line agents for the treatment of depression and it is also used in the treatment of other psychiatric disorders. The main goal of this study was to identify which brain areas are affected by escitalopram administration. This study was carried out on male Wistar rats that received escitalopram daily over 14 days and that were studied by 2-deoxy-2[18F]fluoro-D-glucose ([18F]FDG)-PET on the last day of treatment. Computed tomography (CT) images were acquired immediately before each PET scan and the main effects of drug administration were elucidated by Statistical Parametric Mapping. The results obtained indicated that repeated exposure to escitalopram increased metabolic activity in the retrosplenial and posterior cingulate cortices, while it decreased such activity in the ventral hippocampus, cerebellum, brainstem and midbrain regions, including the raphe nuclei and ventral tegmental area. Therefore, repeated exposure to escitalopram alters the activity of several brain areas closely related to the serotonergic system, and previously identified as key regions in the antidepressant effect induced by SSRIs. Furthermore, some of the changes found, such as the dampened metabolism in the ventral tegmental area, are similar to changes that have been described after treating with other fast-acting antidepressant approaches.

Deep brain stimulation electrode insertion and depression: Patterns of activity and modulation by analgesics.

BACKGROUND: An initial antidepressant effect when using deep brain stimulation (DBS) of the subcallosal area of the cingulate cortex (Cg25) to treat resistant depression that could be the result of electrode insertion has been described. We previously showed that electrode insertion into the infralimbic cortex (ILC; the Cg25 rodent correlate) provokes a temporally limited antidepressant-like effect that is counteracted by non-steroidal anti-inflammatory drugs, such as those routinely used for pain relief. OBJECTIVE: We characterized the effect of electrode insertion using functional neuroimaging and evaluated the impact of different analgesics on this effect. METHODS: The effect of electrode insertion into the ILC was evaluated by positron emission tomography. The effect of analgesics (ibuprofen, tramadol and morphine) on the behavioral effect induced by electrode insertion were evaluated through the forced swimming test and the novelty suppressed feeding test. Furthermore, glial fibrillary acidic protein (GFAP) and p11 expression were measured. RESULTS: Electrode implantation produces an antidepressant- and anxiolytic-like effect, a local decrease in glucose metabolism, and changes in several brain regions commonly related to depression and the antidepressant response. Ibuprofen counteracted the behavioral and molecular changes produced by electrode insertion (changes in GFAP and p11 protein expression). However, analgesics with no anti-inflammatory properties (e.g., tramadol) neither counteract the behavioral effects of electrode implantation nor the molecular mechanisms triggered. CONCLUSIONS: Analgesics without anti-inflammatory properties may not limit the transient benefit produced by electrode insertion reducing the time required to achieve remission in depressive DBS patients.

Early neuromodulation prevents the development of brain and behavioral abnormalities in a rodent model of schizophrenia.

The notion that schizophrenia is a neurodevelopmental disorder in which neuropathologies evolve gradually over the developmental course indicates a potential therapeutic window during which pathophysiological processes may be modified to halt disease progression or reduce its severity. Here we used a neurodevelopmental maternal immune stimulation (MIS) rat model of schizophrenia to test whether early targeted modulatory intervention would affect schizophrenia's neurodevelopmental course. We applied deep brain stimulation (DBS) or sham stimulation to the medial prefrontal cortex (mPFC) of adolescent MIS rats and respective controls, and investigated its behavioral, biochemical, brain-structural and -metabolic effects in adulthood. We found that mPFC-DBS successfully prevented the emergence of deficits in sensorimotor gating, attentional selectivity and executive function in adulthood, as well as the enlargement of lateral ventricle volumes and mal-development of dopaminergic and serotonergic transmission. These data suggest that the mPFC may be a valuable target for effective preventive treatments. This may have significant translational value, suggesting that targeting the mPFC before the onset of psychosis via less invasive neuromodulation approaches may be a viable preventive strategy.

Effects of chronic dietary exposure to monosodium glutamate on feeding behavior, adiposity, gastrointestinal motility, and cardiovascular function in healthy adult rats.

BACKGROUND: Monosodium glutamate (MSG) is a flavor-enhancer widely used as a food additive. However, its safe dietary concentration and its toxicity, including its possible implication in the recent metabolic syndrome pandemia, is still a controversial issue. Therefore, a deep knowledge of its effects upon regular dietary use is needed. Our aim was to evaluate the effects of chronic exposure to MSG on feeding behavior, abdominal fat, gastrointestinal motility, and cardiovascular function in rats. METHODS: Two groups of adult male Wistar rats were used: control and treated with MSG (4 g/L in drinking water) for 6 weeks. Different functional parameters were determined and the histological structure was analyzed in tissues of interest. KEY RESULTS: Compared to control animals, chronic MSG increased water intake but did not modify food ingestion or body weight gain. Neither the abdominal fat volume nor the fat fraction, measured by magnetic resonance imaging, was modified by MSG. Monosodium glutamate did not alter general gastrointestinal motility, but significantly increased the colonic response to mechanical stimulation. It slightly reduced endothelium-dependent relaxation in aorta, without significantly modifying any other cardiovascular parameters. No significant histological alterations were detected in salivary glands, intestinal wall, aorta, heart, and kidney. CONCLUSIONS & INFERENCES: Chronic treatment with MSG in the adult rat increased water intake. This supports its potential to improve acceptance of low-fat regimens and to increase hydration in the elderly and sportspeople, often at risk of dehydration. Changes in colonic contractility and cardiovascular function could have some long-term repercussions warranting further research.

Behavioral, neurochemical and morphological changes induced by the overexpression of munc18-1a in brain of mice: relevance to schizophrenia.

Overexpression of the mammalian homolog of the unc-18 gene (munc18-1) has been described in the brain of subjects with schizophrenia. Munc18-1 protein is involved in membrane fusion processes, exocytosis and neurotransmitter release. A transgenic mouse strain that overexpresses the protein isoform munc18-1a in the brain was characterized. This animal displays several schizophrenia-related behaviors, supersensitivity to hallucinogenic drugs and deficits in prepulse inhibition that reverse after antipsychotic treatment. Relevant brain areas (that is, cortex and striatum) exhibit reduced expression of dopamine D(1) receptors and dopamine transporters together with enhanced amphetamine-induced in vivo dopamine release. Magnetic resonance imaging demonstrates decreased gray matter volume in the transgenic animal. In conclusion, the mouse overexpressing brain munc18-1a represents a new valid animal model that resembles functional and structural abnormalities in patients with schizophrenia. The animal could provide valuable insights into phenotypic aspects of this psychiatric disorder.

Sinogram bow-tie filtering in FBP PET reconstruction.

Low-pass filtering of sinograms in the radial direction is the most common practice to limit noise amplification in filtered back projection (FBP) reconstruction of positron emission tomography studies. Other filtering strategies have been proposed to prevent the loss in resolution due to low-pass radial filters, although results have been diverse. Using the well-known properties of the Fourier transform of a sinogram, the authors defined a binary mask that matches the expected shape of the support region in the Fourier domain of the sinogram ("bow tie"). This mask was smoothed by a convolution with a ten-point Gaussian kernel which not only avoids ringing but also introduces a pre-emphasis at low frequencies. A new filtering scheme for FBP is proposed, comprising this smoothed bow-tie filter combined with a standard radial filter and an axial filter. The authors compared the performance of the bow-tie filtering scheme with that of other previously reported methods: Standard radial filtering, angular filtering, and stackgram-domain filtering. All the quantitative data in the comparisons refer to a baseline reconstruction using a ramp filter only. When using the smallest size of the Gaussian kernel in the stackgram domain, the authors achieved a noise reduction of 33% at the cost of degrading radial and tangential resolutions (14.5% and 16%, respectively, for cubic interpolation). To reduce the noise by 30%, the angular filter produced a larger degradation of contrast (3%) and tangential resolution (46% at 10 mm from the center of the field of view) and showed noticeable artifacts in the form of circular blurring dependent on the distance to the center of the field of view. For a similar noise reduction (33%), the proposed bow-tie filtering scheme yielded optimum results in resolution (gain in radial resolution of 10%) and contrast (1% increase) when compared with any of the other filters alone. Experiments with rodent images showed noticeable image quality enhancement when using the proposed bow-tie filtering scheme.

Assessment of airway distribution of transnasal solutions in mice by PET/CT imaging.

PURPOSE: Transnasal administration is one of the most common routes for allergen challenge in mouse models of airway diseases. Although this technique is widely used, neither the amount of allergen that reaches the lung nor its airway distribution has been well established. We used positron emission tomography (PET) and computed tomography (CT) to examine the anatomical distribution of a solution containing a tracer immediately after transnasal delivery and to determine the possible influence of age and administered volume. PROCEDURES: Forty-six female BALB/c mice were divided into three groups according to instillation volume and age: (A) 15 microl, 8-10 weeks old (N = 10), (B) 30 microl, 8-10 weeks old (N = 20), and (C) 30 microl, 32 weeks old (N = 16). Anesthetized animals underwent a dynamic scan in a dedicated small-animal PET scanner immediately after transnasal administration of a solution containing (18)FDG. Regions of interest were used to obtain quantitative data. Animals were also imaged with a small-animal CT scanner to obtain complementary anatomical information. RESULTS: Mean +/- SD (5.69 +/- 4.51%) of the solution administered reached the lungs in group A, 41.84 +/- 8.03% in group B, and 36.65 +/- 16.15% in group C. A comparable percentage was delivered to the left and right lungs in all the groups. Analysis of variance revealed a significant difference between the groups in the proportion of the solution that reached the lungs depending on the injection volume (P < 0.001), but not depending on animal age. CONCLUSIONS: In this first report on quantitative imaging by PET and CT in small animals, we confirmed the suitability of the transnasal route with an instilled volume of 30 microl delivering fluids into the lower airways, although only about 40% of the dose reaches the lungs.

Detection of visual activation in the rat brain using 2-deoxy-2-[(18)F]fluoro-D: -glucose and statistical parametric mapping (SPM).

PURPOSE: This study was designed to assess changes in brain glucose metabolism in rats after visual stimulation. MATERIALS AND METHODS: We sought to determine whether visual activation in the rat brain could be detected using a small-animal positron emission tomography (PET) scanner and 2-deoxy-2-[(18)F]fluoro-D: -glucose (FDG). Eleven rats were divided into two groups: (a) five animals exposed to ambient light and (b) six animals stimulated by stroboscopic light (10 Hz) with one eye covered. Rats were injected with FDG and, after 45 min of visual stimulation, were sacrificed and scanned for 90 min in a dedicated PET tomograph. Images were reconstructed by a three-dimensional ordered subset expectation maximization algorithm (1.8 mm full width at half maximum). A region-of-interest (ROI) analysis was performed on 14 brain structures drawn on coronal sections. Statistical parametric mapping (SPM) adapted for small animals was also carried out. Additionally, the brains of three rats were sliced into 20-microm sections for autoradiography. RESULTS: Analysis of ROI data revealed significant differences between groups in the right superior colliculus, right thalamus, and brainstem (p < or = 0.05). SPM detected the same areas as the ROI approach. Autoradiographs confirmed the existence of hyperactivation in the left superior colliculus and auditory cortex. CONCLUSIONS: To our knowledge, this is the first report that uses FDG-PET and SPM analysis to show changes in rat brain glucose metabolism after a visual stimulus.

Extraction of the respiratory signal from small-animal CT projections for a retrospective gating method.

We propose a retrospective respiratory gating algorithm to generate dynamic CT studies. To this end, we compared three different methods of extracting the respiratory signal from the projections of small-animal cone-beam computed tomography (CBCT) scanners. Given a set of frames acquired from a certain axial angle, subtraction of their average image from each individual frame produces a set of difference images. Pixels in these images have positive or negative values (according to the respiratory phase) in those areas where there is lung movement. The respiratory signals were extracted by analysing the shape of the histogram of these difference images: we calculated the first four central and non-central moments. However, only odd-order moments produced the desired breathing signal, as the even-order moments lacked information about the phase. Each of these curves was compared to a reference signal recorded by means of a pneumatic pillow. Given the similar correlation coefficients yielded by all of them, we selected the mean to implement our retrospective protocol. Respiratory phase bins were separated, reconstructed independently and included in a dynamic sequence, suitable for cine playback. We validated our method in five adult rat studies by comparing profiles drawn across the diaphragm dome, with and without retrospective respiratory gating. Results showed a sharper transition in the gated reconstruction, with an average slope improvement of 60.7%.

Differences in response to food stimuli in a rat model of obesity: in-vivo assessment of brain glucose metabolism.

OBJECTIVE: Food intake is regulated by factors that modulate caloric requirements as well as food's reinforcing properties. In this study, we measured brain glucose utilization to an olfactory stimulus (bacon scent), and we examined the role of food restriction and genetic predisposition to obesity on such brain metabolic activity. METHODS: Zucker obese (Ob) and lean (Le) rats were divided into four groups: (1) Ob ad-libitum fed, (2) Ob food restricted (70% of ad libitum), (3) Le ad-libitum fed and (4) Le food restricted. Rats were scanned using micro-positron emission tomography and 2-[(18)F]-fluoro-2-deoxy-D-glucose under two conditions: (1) baseline scan (no stimulation) and (2) challenge scan (food stimulation, FS). RESULTS: FS resulted in deactivation of the right and left hippocampus. Ob rats showed greater changes with FS than Le rats (deactivation of hippocampus and activation of the medial thalamus) and Ob but not Le animals deactivated the frontal cortex and activated the superior colliculus. Access to food resulted in an opposite pattern of metabolic changes to the food stimuli in olfactory nucleus (deactivated in unrestricted and activated in restricted) and in right insular/parietal cortex (activated in unrestricted and deactivated in restricted). In addition, restricted but not unrestricted animals activated the medial thalamus. CONCLUSIONS: The greater changes in the Ob rats suggest that leptin modulates the regional brain responses to a familiar food stimulus. Similarly, the differences in the pattern of responses with food restriction suggest that FS is influenced by access to food conditions. The main changes with FS occurred in the hippocampus, a region involved in memory, the insular cortex, a region involved with interoception (perception of internal sensations), the medial thalamus (region involved in alertness) and in regions involved with sensory perception (olfactory bulb, olfactory nucleus, occipital cortex, superior colliculus and parietal cortex), which corroborates their relevance in the perception of food.

Effects of MDMA on blood glucose levels and brain glucose metabolism.

PURPOSE: This study was designed to assess changes in glucose metabolism in rats administered single or repeated doses of MDMA. METHODS: Two different experiments were performed: (1) A single-dose study with four groups receiving 20 mg/kg, 40 mg/kg, saline or heat, and (2) a repeated-dose study with two groups receiving three doses, at intervals of 2 h, of 5 mg/kg or saline. Rats were imaged using a dedicated small-animal PET scanner 1 h after single-dose administration or 7 days after repeated doses. Glucose metabolism was measured in 12 cerebral regions of interest. Rectal temperature and blood glucose were monitored. RESULTS: Peak body temperature was reached 1 h after MDMA administration. Blood glucose levels decreased significantly after MDMA administration. In the single-dose experiment, brain glucose metabolism showed hyperactivation in cerebellum and hypo-activation in the hippocampus, amygdala and auditory cortex. In the repeated-dose experiment, brain glucose metabolism did not show any significant change at day 7. CONCLUSION: These results are the first to indicate that MDMA has the potential to produce significant hypoglycaemia. In addition, they show that MDMA alters glucose metabolism in components of the motor, limbic and somatosensory systems acutely but not on a long-term basis.

MDMA and serotonin: based on two cases.

3,4-methylenedioxyamphetamine (MDMA) or "ecstasy" damages serotonin neurons in all animal species and there is growing evidence that this finding also applies to humans. This fact, together with the increasing extended use in the young population, has important repercussions in the appearance of specific psychopathologic and cognitive disturbances associated to its use. The authors present two clinical cases, in which psychopathological and cognitive symptoms are detected in MDMA users that support this hypothesis. Problems in the diagnosis of psychiatric disorders associated to MDMA and its clinical and therapeutic implications are discussed.

Influencia del cocultivo de islotes pancreáticos con células hepáticas sobre la liberación de insulina y sobre la implantación de los islotes en hígado sin inmunosupresión / Influence of co-culture of pancreatic islets with hepatic cells on insulin release and on implantation of islets in liver without immunosuppression

El objetivo de este trabajo es estudiar la influencia de las células hepáticas sobre la liberación de insulina cuando se co-cultivan con islotes, así como la influencia que puedan tener sobre la implantación de los islotes en el hígado en ratas Wistar, sin el empleo de drogas inmunosupresoras. In vitro tenemos 2 grupos: A) Cultivo de islotes solos y B) Co-cultivo de islotes y células hepáticas, ambos durante 7 días. Se realiza un estudio morfológico, numérico y de liberación de insulina. In vivo tenemos 7 grupos de Tx: A) Tx ficticio con suero fisiológico (4), B) Tx-ch solas (4), C) Tx-1 solos (6), D) Tx-I solos tras cultivo 7 días (5), E) Tx-1 co-cultivados con ch 24 h (5), F) Tx-I co-cultivados con ch 7 días (7) y G) Tx-I co-cultivados con ch 48 h, en placas transwell (5). La proporción de ch/I ha sido de 150:1. ENI ha sido de 1678 ñ 343 con pureza del 90 por ciento. Análisis de datos mediante el test de ANOVA del SPSS 8.0.In vitro: observamos una gran diversidad celular hepática, un descenso en el ENI durante el co-cultivo, sin embargo la insulino-liberación es mayor en los islotes co-cultivados con ch (p < 0.005). In vivo: Los días de euglucemia tras el Tx han sido: grupo A (0 ñ 0), B (0 ñ 0), C( 2.0 ñ 3.098), D 1.8 ñ 2.17), E (8.6 ñ 12.33), F (9.14 ñ 11.02) y G (0 ñ 0). Los resultados de E y F, confirman un efecto favorable de las ch sobre la implantación de los islotes alogénicos en hígado, consiguiéndose un 20 por ciento y un 14.3 por ciento de reversión de la diabetes. El resultado de G parece indicar la posibilidad de que más que una interacción celular entre las ch e islotes, se trate más bien de la secreción constante de algún producto, y este sea el responsable de la supervivencia de los islotes implantados en hígado. (AU)

Inducción de tolerancia al trasplante de islotes, en ratas Wistar, mediante células hepáticas / Induction of tolerance to islet transplantation, in Wistar rats, by hepatic cells

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Co-trasplante alogénico de células hepáticas e islotes en ratas diabéticas / Allogen co-transplant of liver cells and islets in diabetic rats

Buscando una mayor tolerancia de los islotes sin necesidad de inmunosupresión, hemos realizado el co-trasplante (co-Tx) de islotes cultivados 3-5 días, mezclados una hora antes del trasplante con hepatocitos (y otras células hepáticas) recién aisladas, en una proporción aproximadamente de 100 y 200 hepatocitos por islote. La diabetes se ha inducido con estreptozotocina 60 mg/kg vía ip en ratas Wistar. Se han estudiado tres grupos de coTx: C) co-Tx islotes y células hepáticas frescas en proporción 1:100; D) co-Tx islotes y células hepáticas frescas en proporción 1:200, y E) co-Tx de islotes co-cultivados con células hepáticas 24 horas en proporción 1:100. Estos tres grupos se han comparado con dos grupos control: A) Tx con sólo células hepáticas y B) Tx con sólo islotes. El número de islotes trasplantados fue respectivamente de: B) 1.808 ñ 413; C) 1.515 ñ 198; D) 1.830 ñ 435, y E) 1.600 ñ 134.En los grupos A y B hubo una falta total de reversión de la diabetes. El grupo C (co-Tx con 1:100) mostró los mejores resultados con euglucemia global durante cuatro días, que en una de las ratas persistió un mes con valores menores de 200 mgldl. La reversión de la diabetes también se observó menos días en el grupo D sin que persistiera más de ocho días en ninguna rata. En el grupo E, co-Tx después del co-cultivo, los resultados fueron intermedios entre los grupos E y D. Estos resultados sugieren un efecto beneficioso de los hepatocitos (o de otras células hepáticas) sobre los islotes pancreáticos, facilitando su tolerancia o aumentando su viabilidad, sin necesidad de inmunosupresión medicamentosa. Considerando la novedad de estos resultados se hace necesario ampliar los estudios para aumentar la eficacia de la tolerancia y explicar el mecanismo de acción (AU)