Administration of the GABAA receptor antagonist picrotoxin into rat supramammillary nucleus induces c-Fos in reward-related brain structures. Supramammillary picrotoxin and c-Fos expression

<p>Abstract</p> <p>Background</p> <p>Picrotoxin blocks GABA_Areceptors, whose activation typically inhibits neuronal firing activity. We recently found that rats learn to selectively self-administer picrotoxin or bicuculline, another GABA_Areceptor antagonist, into the supramammillary nucleus (SuM), a posterior hypothalamic structure localized anterior to the ventral tegmental area. Other drugs such as nicotine or the excitatory amino acid AMPA are also self-administered into the SuM. The SuM appears to be functionally linked with the mesolimbic dopamine system and is closely connected with other brain structures that are implicated in motivational processes, including the prefrontal cortex, septal area, preoptic area, lateral hypothalamic area and dorsal raphe nucleus. Here, we hypothesized that these brain structures are activated by picrotoxin injections into the SuM.</p> <p>Results</p> <p>Picrotoxin administration into the SuM markedly facilitated locomotion and rearing. Further, it increased c-Fos expression in this region, suggesting blockade of tonic inhibition and thus the disinhibition of local neurons. This manipulation also increased c-Fos expression in structures including the ventral tegmental area, medial shell of the nucleus accumbens, medial prefrontal cortex, septal area, preoptic area, lateral hypothalamic area and dorsal raphe nucleus.</p> <p>Conclusions</p> <p>Picrotoxin administration into the SuM appears to disinhibit local neurons and recruits activation of brain structures associated with motivational processes, including the mesolimbic dopamine system, prefrontal cortex, septal area, preoptic area, lateral hypothalamic area and dorsal raphe nucleus. These regions may be involved in mediating positive motivational effects triggered by intra-SuM picrotoxin.</p

The albino locus and locomotor behavior in the mouse: Studies using extended test intervals

The influence of albinism upon initial activity in novel surroundings was examined using coisogenic and congenic lines of mice. In comparison with those of previous studies, an extended test interval was used, and this modification produced significant main and interaction effects of the c locus upon activity for both lines. The present findings confirm and extend those of previous studies upon the depressant effects of albinism based upon coisogenic lines, and extend the findings to congenic lines as well.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44104/1/10519_2005_Article_BF01065627.pd

Behaviour of 238 U family radionuclides in continental environment: Case of the U mining area near Limoges (France)

International audienceThe objectives of this work are to study the behaviour of 238 U and its daughters in the continental environment and to determine the radiological impact of U mining past activities in the Haute-Vienne French administrative division. The distribution of radionuclides among different size fractions was investigated upstream and downstream mines. Particulate (>0.45µm) and dissolved (<0.45µm) fractions were separated by filtration and analysed by gamma spectrometry. A preconcentration step by evaporation was elaborated and validated for liquid samples. Results indicate that radiological impacts of U mines are the enhancement of radionuclides activities and a change of their distribution between particulate and dissolved fractions at 0.45µm. While activity levels depend on the input intensity, the distribution is controlled by the mine water treatment witch reduces drastically the contribution of mine radionuclides in streams. Analysis of particles from traps and sediments confirms that the distribution of mine radionuclides promote their accumulation in lacustrian sediments. Nevertheless, the impact of the past activities is very limited in space. Indeed, it becomes weak at 10 km downstream the inputs and is no more detectable at 30 km downstream

Sediment records in the river Loire estuary

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Sediment records in the river Loire estuary

Within the framework of the "Loire river and estuary radioecology" program, radionuclide measurements were undertaken in the various components of the estuarine aquatic ecosystem: dissolved, particulate and sedimentary fractions. In order to investigate the extent of long-term radionuclide accumulation in this area, 8 sediment cores were sampled in the estuary, plus 2 cores on the sea shore near the river mouth; gamma spectrometric measurements were performed at the Laboratoire Souterrain de Modane (LSM, CNRS-CEA) in the French Alps using very low background, high efficiency "well-type" Ge detectors with crystal volumes of 430 and 910 cm3. Such large detectors allow the measurement of samples of about 20g with very high detection efficiencies. Among the artificial radionuclides present in industrial releases, 60Co was detected in most samples throughout the cores. Using 137Cs and 210Pb profiles in the cores, mean apparent accumulation rates were estimated after a normalization to the fine-grain sedimentary fraction which is the main carrier of reactive radionuclides. A sedimentary record of the last 50 years was obtained. 60Co activities were always very low, from below 0.1 up to 2 Bq.kg-1. Plots of 60Co versus sedimentary layer ages are presented and compared with annual discharges of nuclear power plants located along the Loire river

Improvement in the Determination of 238 U, 228 - 234 Th, 226 - 228 Ra, 210 Pb, and 7 Be by γ Spectrometry on Evaporated Fresh Water Samples

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Discovery of a composite reefal terrace of middle and late Pleistocene age in Great Inagua Island, Bahamas. Implications for regional tectonics and sea-level history

International audienceWe provide here new 234U/230Th ages measured on coral samples collected from a reefal terrace exposed on Great Inagua Island (Bahamas) that was, up to now, wholly attributed to the last interglacial period (Marine Isotope Stage 5e). Our results from the upper part of the terrace confirm the previously reported MIS 5e age, whereas ages obtained from the lower part range between 139,000 and 193,000 years BP, spanning most of MIS 6. Petrographic examination showed that secondary aragonite cement and internal sediment occur in the coral chambers of these samples, indicating they were rejuvenated and likely date from the penultimate interglaciation (MIS 7). The studied terrace is thus a composite build-up and its lower part represents the first coral reef of MIS 7 age ever described in the Bahamas archipelago. Our results further suggest (1) that Great Inagua Island recently underwent a phase of tilting, and (2) that sea level was close present datum during MIS 7. © 2006 Elsevier B.V. All rights reserved