Repeated diazepam administration reversed working memory impairments and glucocorticoid alterations in the prefrontal cortex after short but not long alcohol-withdrawal periods.

The study was designed to assess whether repeated administration of diazepam (Valium®, Roche)-a benzodiazepine exerting an agonist action on GABAA receptors-may alleviate both the short (1 week, 1W) and long-term (6 weeks, 6W) deleterious effects of alcohol withdrawal occurring after chronic alcohol consumption (6 months; 12% v/v) in C57/BL6 male mice. More pointedly, we first evidenced that 1W and 6W alcohol-withdrawn mice exhibited working memory deficits in a sequential alternation task, associated with sustained exaggerated corticosterone rise and decreased pCREB levels in the prefrontal cortex (PFC). In a subsequent experiment, diazepam was administered i.p. for 9 consecutive days (1 injection/day) during the alcohol withdrawal period at decreasing doses ranging from 1.0 mg/kg to 0.25 mg/kg. Diazepam was not detected in the blood of withdrawn mice at the time of memory testing, occurring 24 hours after the last diazepam injection. Repeated diazepam administration significantly improved alternation rates and normalized levels of glucocorticoids and pCREB activity in the PFC in 1W but not in 6W withdrawn mice. Thus, repeated diazepam administration during the alcohol-withdrawal period only transitorily canceled out the working memory impairments and glucocorticoid alterations in the PFC of alcohol-withdrawn animals.

Different implications of the dorsal and ventral hippocampus on contextual memory retrieval after stress.

This study assessed the relative contributions of dorsal (dHPC) and ventral (vHPC) hippocampus regions in mediating the rapid effects of an acute stress on contextual memory retrieval. Indeed, we previously showed that an acute stress (3 electric footschocks; 0.9 mA each) delivered 15 min before the 24 h-test inversed the memory retrieval pattern in a contextual discrimination task. Specifically, mice learned in a four-hole board two successive discriminations (D1 and D2) varying by the color and texture of the floor. Twenty-four hours later, nonstressed animals remembered accurately D1 but not D2 whereas stressed mice showed an opposite memory retrieval pattern, D2 being more accurately remembered than D1. We showed here that, at the time of memory testing in that task, stressed animals exhibited no significant changes neither in pCREB activity nor in the time-course evolution of corticosterone into the vHPC; in contrast, a significant decrease in pCREB activity and a significant increase in corticosterone were observed in the dHPC as compared to nonstressed mice. Moreover, local infusion of the anesthetic lidocaine into the vHPC 15 min before the onset of the stressor did not modify the memory retrieval pattern in nonstress and stress conditions whereas lidocaine infusion into the dHPC induced in nonstressed mice an memory retrieval pattern similar to that observed in stressed animals. The overall set of data shows that memory retrieval in nonstress condition involved primarily the dHPC and that the inversion of memory retrieval pattern after stress is linked to a dHPC but not vHPC dysfunction.

Rapid stress-induced corticosterone rise in the hippocampus reverses serial memory retrieval pattern.

We previously showed that an acute stress (electric footshocks) induced both a rapid plasma corticosterone rise and a reversal of serial memory retrieval pattern in a contextual serial discrimination (CSD) task. This study is aimed at determining (i) if the rapid stress effects on CSD performance are mediated by the hippocampus; (ii) if hippocampal corticosterone membrane receptor activation is involved in the rapid stress effects on CSD performance. In experiment 1, microdialysis in the dorsal hippocampus (dHPC) was used to measure the stress-induced corticosterone rise; in parallel, the effect of acute stress on CSD performance was evaluated. In addition, the functional involvement of corticosterone in the behavioral effects of stress was assessed by administering metyrapone, a corticosterone synthesis inhibitor, before stress. In experiment 2, the involvement of hippocampal corticosterone membrane receptors in the stress-induced reversal of CSD performance was studied by injecting corticosterone-bovine serum albumin (BSA) (a membrane-impermeable complex) in the dHPC in non stressed mice. Results showed that (i) the acute stress induced a rapid (15 min) and transitory (90 min) corticosterone rise into the hippocampus dHPC, and a reversal of serial memory retrieval pattern; (ii) both the endocrinal and memory stress-induced effects were blocked by metyrapone; (iii) corticosterone-BSA injection into the dHPC in non stressed mice mimicked the effects of stress on serial retrieval pattern. Overall, our study is first to show that (i) a rapid stress-induced corticosterone rise into the dHPC transitorily reverses serial memory retrieval pattern and (ii) hippocampal corticosterone membrane receptors activation is involved in the rapid effects of acute stress on serial memory retrieval.

Increased stress-induced intra-hippocampus corticosterone rise associated with memory impairments in middle-aged mice.

The present study investigates the relationships between hippocampal corticosterone concentrations and memory retrieval performance in stress and non-stress conditions, in both young (6 month-old) and middle-aged (16 month-old) mice. For this purpose, the time-course evolution of stress-induced corticosterone rise in the dorsal hippocampus (dHPC) was investigated in both young and middle-aged mice. In parallel, the evolution of memory retrieval patterns was assessed using a contextual serial discrimination task (CSD). Finally, metyrapone (corticosterone synthesis inhibitor) was administered in order to evaluate the stress-induced impact of corticosterone rise on contextual memory retrieval in middle-aged animals. Results showed that: (i) non-stressed middle-aged mice exhibited a memory retrieval pattern opposite to that of non-stressed young animals, but similar to that of stressed young mice; (ii) the impact of stress on memory performance was transient (90 min) in young, as compared to middle-aged mice (120 min); (iii) dHPC basal (non-stress) corticosterone level was significantly increased by ageing; (iv) acute stress induced a rapid (15 min) and transient (90 min) dHPC corticosterone rise in young mice, while exhibiting greater magnitude and duration (120 min) in middle-aged animals; and (v) both the stress-induced endocrinal and memory effects were blocked by metyrapone in young and middle-aged mice. Finally, to our knowledge, the present work is the first study to directly measure the corticosterone rise in the hippocampus following exposure to stress and to directly correlate the corticosterone changes in the hippocampus with memory performance in both young and middle-aged mice.

Prefrontal cortex or basolateral amygdala lesions blocked the stress-induced inversion of serial memory retrieval pattern in mice.

Previous data from our team have shown that pre-test stress in mice reversed the pattern of memory retrieval in a contextual serial spatial task (CSD; Celerier, A., Pierard, C., Rachbauer, D., Sarrieau, A., & Beracochea, D. (2004). Contextual and serial discriminations: A new learning paradigm to assess simultaneously the effects of acute stress on retrieval of flexible or stable information in mice. Learning and Memory, 11, 196-204). The present study is aimed at determining brain areas which might be critically involved in mediating the stress effect on memory retrieval in the CSD task. For that purpose, we studied hereby the effects of ibotenic acid lesions of either the prefrontal cortex (PFC) or the basolateral amygdala (BLA) in Stressed or Non-Stressed Balb/c mice on memory retrieval in the CSD task. In that task, mice learned two successive spatial discriminations (D1 and D2) within two different internal contexts in a four-hole board. The stressor (electric footshocks) was delivered 5 min before test, occurring 24 h after acquisition. During test, mice were relocated either on the floor of the first or of the second discrimination. Results showed that (i) spatial memory was substantial and remained unaffected both by lesions and stress; (ii) Non-Stressed controls as well as Non-Stressed or Stressed PFC and BLA-lesioned mice remembered accurately D1 but not D2; and (iii) in contrast, Stressed controls accurately remembered D2 but not D1. In parallel to behavioral experiments, we also showed that PFC and BLA lesions did not affect the stress-induced increase of plasma corticosterone levels. All together, PFC and BLA integrity are not necessary for retrieval processes per se; in contrast, the PFC and BLA are critically involved in the mediation of the deleterious stress effects on serial order memory retrieval.

First evidence of a delay-dependent working memory-enhancing effect of modafinil in mice.

This study investigated the effects of pretest injection of modafinil on delayed spontaneous alternation rates (SA) used to evaluate working memory in C57 Bl/6 mice. In a first experiment, systemic modafinil at 64 mg/kg, but not at 8 mg/kg or 32 mg/kg doses produced a significant increase of alternation scores (intertrial interval (ITI) 60s) when compared with controls. In a second experiment, modafinil (64 mg/kg) enhanced the alternation rates mainly at long (60 s and 180 s) but not at short (5 s) ITIs. Exploratory latencies and activity in a four hole-board apparatus were not modified by modafinil administration. These experiments are the first to demonstrate a delay-dependent working memory-enhancing effect of modafinil.

Brain stem energy metabolism response to acute hypoxia in anaesthetized rats: a 31P NMR study.

Mammals react to acute hypoxia with an initial augmentation and a secondary depression of the respiratory rhythm generated by brain stem neuronal networks. To investigate the cytosolic level of energy rich phosphorus metabolites during these responses, we developed 31P nuclear magnetic resonance spectroscopy of the brain stem. Moderate hypoxia (paO2 = 40 mmHg, 2 min) caused a reversible 62 +/- 15% respiratory rhythm depression and decreased cytosolic phosphocreatine levels by 43 +/- 11% (p < 0.01, n = 7) without affecting adenosine triphosphate levels. Cellular metabolic depletion therefore contributes to the brain stem response to hypoxia, and appears to reflect adaptive mechanisms to limited oxygen availability in the brain stem.

Simultaneous NMR microdialysis study of brain glucose metabolism in relation to fasting or exercise in the rat.

To study the impact of exercise or fasting and of subsequent glucose supplementation on glucose metabolism in rats, a spectrophotometric method was used to determine peripheral blood glucose; a technique associating (1)H-NMR spectroscopy and cortical microdialysis was also used to observe intra- plus extracellular and extracellular brain glucose variations, respectively. Compared with control animals (204 +/- 19 microM in dialysate, n = 10), exercise increased brain extracellular glucose levels to 274 +/- 22 microM (n = 8; P < 0.05), whereas fasting induced a drop in glucose levels down to 140 +/- 9 microM (n = 8; P < 0.05). After fasting, glucose supplemented by infusion increased glycemia from 7.4 +/- 0.4 to 19.9 +/- 0.8 mM (n = 10; P < 0.001), as well as extracellular and extra- plus intracellular brain glucose to 263 +/- 20% (n = 8; P < 0.001) and 342 +/- 28% (n = 8; P < 0.001), respectively, over basal for that group. After exercise, a similar infusion increased glycemia from 7. 3 +/- 0.3 to 16.8 +/- 1.1 mM (n = 10; P < 0.001), as well as extracellular and extra- plus intracellular brain glucose to 178 +/- 19% (n = 8; P < 0.001) and 244 +/- 20% (n = 8; P < 0.001), respectively, over basal for that group. These results confirmed the existence of a link between glucose level variations in peripheral and cerebral areas but also showed that exercise increased extracellular brain glucose levels despite peripheral hypoglycemia, suggesting a specific regulation mechanism of cerebral glucose metabolism during exercise.

Caffeine or melatonin effects on sleep and sleepiness after rapid eastward transmeridian travel.

We measured the effects of slow-release caffeine (SRC) and melatonin (Mlt) on sleep and daytime sleepiness after a seven-time zone eastbound flight. In a double-blind, randomized, placebo-controlled study, each of three groups of nine subjects was given either 300 mg SRC on recovery day 1 (D1) to D5 (0800) or 5 mg Mlt on preflight D-1 (1700), flight day D0 (1600), and from D1 to D3 (2300), or placebo (Pbo) at the same times. Nighttime sleep was evaluated by polysomnography and daytime sleepiness from measurements of sleep latencies and continuous wrist actigraphy. Compared with baseline, we found a significant rebound of slow-wave sleep on night 1 (N1) to N2 under Pbo and Mlt and a significant decrease in rapid eye movement sleep on N1 (Pbo) and N1-N3 (Mlt). Sleepiness was objectively increased under Pbo (D1-D6) and Mlt (D1-D3). SRC reduced sleepiness but also tended to affect sleep quality until the last drug day. In conclusion, both drugs have positive effects on some jet lag symptoms after an eastbound flight: SRC on daytime sleepiness, and Mlt on sleep.

Effects of a vigilance-enhancing drug, modafinil, on rat brain metabolism: a 2D COSY 1H-NMR study.

The effects of modafinil, a vigilance-enhancing drug, on brain metabolism were investigated directly in situ by the 2D COSY 1H-NMR spectroscopy in anesthetized rats. Modafinil (600 mg/kg, i.p.) induced significant increases in both aspartate (72% +/- 15%) and glutamate-glutamine pool (28% +/- 8%) simultaneously with increases in inositol (51% +/- 19%) and creatine-phosphocreatine pool (47% +/- 14%) in comparison with control values (P < 0.05; n = 5). These results suggest that the awakening properties of modafinil could be mediated by metabolic activation.

Functional magnetic resonance imaging of mental strategy in a simulated aviation performance task.

BACKGROUND: The objective of this study was to analyze the sensory and cognitive functions associated with activated brain regions characterizing mental strategy relative to degree of expertise in aviation-related tasks. METHODS: We used echo-planar functional magnetic resonance imaging (fMRI) technique to examine brain activity in expert pilots (n = 6) compared with novice pilots (n = 6) during performance of a simulated aviation track-following task at 200 knots vs. 100 knots. RESULTS: Expert pilots showed reduced activity in visual and motor regions that contrasted with predominant activation within anterior structures including the frontal and prefrontal cortices; structures involved in visual working memory, planning, selective attention and decision making functions. Novice pilots showed widespread activation of anterior and posterior brain structures, with a rise in activity in the visual, parietal and motor cortices as task difficulty increased. CONCLUSIONS: A high level of performance in the track-following task related to a high degree of expertise in the aviation field. This corresponded to experts performing perceptual and mnemonic processing through a network of specialized functions from visual through multiple prefrontal areas. By contrast, the novice pilots predominantly show activity associated with non-specific perceptual processing and without subsequent representation of selective information in working memory.

[Study of urinary excretion of codeine and morphine after oral ingestion of codeine]. / Etude de l'élimination urinaire de la codéine et de la morphine après absorption orale de codéine.

Results of an investigation on the urinary excretion of codeine and morphine after oral ingestion of 1 mg.kg-1 b.w codeine are reported. The investigation run on seven clinically healthy subjects showed: low digestive absorption of codeine (# 20%); rapid biotransformation of codeine into morphine (first urines excreted after absorption); rapid disappearance of codeine from urines (#30 hrs); persistence of morphine alone (#68 hrs); rapid evolution of the codeine/morphine ratio (inversion of the ratio after #18 hrs); total elimination of morphine which can be greater than for codeine; very different half-life periods for codeine and morphine (5.1 and 13.6 hrs); no other codeine metabolites (nor-codeine and nor-morphine); very high individual variations; one subject with low activity of cytochrome P 450 dbl/buFL. Finally, in an epidemiological survey of drug addict behaviors and detection of drug addiction, it seems very difficult, may be even illusory and hazardous, to try and justify morphine found in urines (morphine, heroin, codeine, codethyline, pholcodine...) except in the very legitimate case where the ratio of urine concentrations of codeine and morphine is greater than one.

Ciproxifan improves working memory through increased prefrontal cortex neural activity in sleep-restricted mice.

Histamine receptor type 3 (H3) antagonists are promising awakening drugs for treatment of sleep disorders. However, few works have tried to identify their cognitive effects after sleep restriction and their impact on associated neural networks. To that aim, Bl/6J male mice were submitted to acute sleep restriction in a shaker apparatus that prevents sleep by transient (20-40 ms) up and down movements. Number of stimulations (2-4), and delay between 2 stimulations (100-200 ms) were randomized. Each sequence of stimulation was also randomly administered (10-30 s interval) for 20 consecutive hours during light (8 h) and dark (12 h) phases. Immediately after 20 h-sleep restriction, mice were injected with H3 antagonist (ciproxifan 3 mg/kg ip) and submitted 30-min later to a working memory (WM) task using spatial spontaneous alternation behaviour. After behavioural testing, brains were perfused for Fos immunohistochemistry to assess neuronal brain activation in the dorsal dentate gyrus (dDG) and the prefrontal cortex. Results showed that sleep restriction decreased slow wave sleep (from 35.8±1.4% to 9.2±2.7%, p<0.001) and was followed by sleep rebound (58.2±5.9%, p<0.05). Sleep restriction did not modify anxiety-like reactivity and significantly decreased WM at long (30 s) but not short (5 s) inter-trial intervals. Whereas sleep restriction failed to significantly modify immunopositive cells in vehicles, ciproxifan administration prevented WM deficits in sleep restricted mice through significant increases of Fos labelling in prelimbic, infralimbic and cingulate 2 cortex. In conclusion, ciproxifan at 3 mg/kg enhanced WM in sleep restricted mice through specific modulation of prefrontal cortex areas.

Stress-induced memory retrieval impairments: different time-course involvement of corticosterone and glucocorticoid receptors in dorsal and ventral hippocampus.

The present study was aimed at determining the relative contribution of the dorsal (DH) and ventral (VH) hippocampus in stress-induced memory retrieval impairments. Thus, we studied the temporal involvement of corticosterone and its receptors, i.e. mineralocorticoid (MR) and glucocorticoid (GR) in the DH and VH, in relation with the time-course evolution of stress-induced memory retrieval impairments. In a first experiment, double microdialysis allowed showing on the same animal that an acute stress (electric footshocks) induced an earlier corticosterone rise in the DH (15-60 min post-stress) and then in the VH (90-105 min post-stress). The return to baseline was faster in the DH (105 min) than in the VH (120 min). Memory deficits assessed by delayed alternation occurred at 15-, 60-, and 105-min delays after stress and were closely related to the kinetic of corticosterone rises within the DH and VH. In a second experiment, the GR antagonist RU-38486 and the MR antagonist RU-28318 were administered in the DH or VH 15 min before stress. RU-38486 restored memory at 60 but not at 105 min post-stress delays in the DH, whereas the opposite pattern was observed in the VH. By contrast, RU-28318 had no effect on memory impairments at both the 60- and 105-min post-stress delays, showing that MR receptors are not involved at these delays. However, RU-28318 administered in the DH restored memory when administered at a shorter post-stress delay (15 min). Overall, our data are first to evidence that stress induces a functional switch from the DH to VH via different corticosterone time-course evolutions in these areas and the sequential GR receptors involvement in the DH and then in the VH, as regards the persistence of stress-induced memory retrieval deficits over time.

Authorship affiliations in original articles submitted to the International Journal of Tuberculosis and Lung Disease.

OBJECTIVE: To ascertain whether the first (principal) and last (senior) authors of articles are affiliated to an organisation belonging to the study country in an analysis of high- and upper-middle-income countries, and low- and lower-middle-income countries. DESIGN: Prospective review of all original articles (n = 911) submitted to the International Journal of Tuberculosis and Lung Disease (IJTLD) from June 2006 to May 2008. RESULTS: In 81% of the submitted articles both the first and the last authors were affiliated to the country of the study. Slightly more articles from low (10%) than from lower-middle-income, high- and upper-middle-income countries (all 4%) had neither the first author nor the last author affiliated to the study country. For 17% of articles from low-income countries the senior author was not from the study country. CONCLUSION: Although acceptance of articles for publication in the IJTLD is not dependent on this criterion, we find that a substantial proportion of authors from low- and middle-income countries were listed as principal and senior authors in articles submitted.

Intrahippocampal cholinesterase inhibition induces epileptogenesis in mice without evidence of neurodegenerative events.

The mechanisms of epileptogenesis remain largely unknown and are probably diverse. The aim of this study was to investigate the role of focal cholinergic imbalance in epileptogenesis. To address this question, we monitored electroencephalogram (EEG) activity up to 12 weeks after the injection of a potent cholinesterase (ChE) inhibitor (soman) at different doses (0.53, 0.75, 1, 2, 2.8, 4 and 11 nmol) into the right dorsal hippocampus of C57BL/6 mice. Different parameters were used to choose the dose for a focal model of epileptogenesis (mainly electrographic patterns and peripheral ChE inhibition). The pattern of neuronal activation was studied by Fos immunohistochemistry (IHC). Brain damage was evaluated by hemalun-phloxin, neuronal nuclei antigen IHC and silver staining. Glial fibrillary acidic protein IHC was used to evaluate astroglial reaction. Finally, long-term behavioral consequences were characterized. At the highest dose (11 nmol), soman quickly evoked severe signs, including initial seizures and promoted epileptogenesis in the absence of tissue damage. With lower doses, late-onset seizures were evidenced, after 1-4 weeks depending on the dose, despite the absence of initial overt seizures and of brain damage. Only a weak astroglial reaction was observed. Following injection of 1 nmol, Fos changes were first evidenced in the ipsilateral hippocampus and then spread to extrahippocampal areas. A selective deficit in contextual fear conditioning was also evidenced two months after injection. Our data show that focal hypercholinergy may be a sufficient initial event to promote epilepsy and that major brain tissue changes (cellular damage, edema, neuroinflammation) are not necessary conditions.