Nicotinic receptors mediate stress-nicotine detrimental interplay via dopamine cells' activity.

Epidemiological studies report strong association between mood disorders and tobacco addiction. This high comorbidity requires adequate treatment but the underlying mechanisms are unknown. We demonstrate that nicotine exposure, independent of drug withdrawal effects, increases stress sensitivity, a major risk factor in mood disorders. Nicotine and stress concur to induce long-lasting cellular adaptations within the dopamine (DA) system. This interplay is underpinned by marked remodeling of nicotinic systems, causing increased ventral tegmental area (VTA) DA neurons' activity and stress-related behaviors, such as social aversion. Blocking ß2 or α7 nicotinic acetylcholine receptors (nAChRs) prevents, respectively, the development and the expression of social stress-induced neuroadaptations; conversely, facilitating α7 nAChRs activation specifically in the VTA promotes stress-induced cellular and behavioral maladaptations. Our work unravels a complex nicotine-stress bidirectional interplay and identifies α7 nAChRs as a promising therapeutic target for stress-related psychiatric disorders.

Detection of human enteric viruses in shellfish collected in Tunisia.

AIMS: The aim of this study was to detect the main pathogenic human RNA enteric viruses able to persist in the environment such as astrovirus, enterovirus, norovirus and hepatitis A virus (HAV) in shellfish collected from two locations in northern Tunisia. METHODS AND RESULTS: Viruses were eluted from digestive tissues and concentrated by polyethylene glycol precipitation before nucleic acid extraction and purification. After checking for inhibitors, all viruses were detected by reverse transcription-polymerase chain reaction (RT-PCR) and confirmed by hybridization. Overall, 83% of the samples were found positive for at least one virus. Astrovirus was detected in 61% of the samples, norovirus in 35% and HAV in 26%. Surprisingly, only one sample was found positive for enterovirus. CONCLUSIONS: The mean number of positive samples found in this study is in accordance with the data found in the literature, indicating that no real difference exists in this respect among countries studied. A notable exception is HAV, which reflects the epidemiological status of the population. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the interest to analyse shellfish samples from different production areas. These data will be helpful to understand virus circulation and to improve shellfish safety. The results, which confirm contamination, necessitate the development of appropriate studies and monitoring in all shellfish-producing countries.

Sewage impact on shellfish microbial contamination.

Coastal areas are frequently contaminated by microorganisms of human origin, due to high population density and low seawater renewal. To evaluate the impact of wastewater input on shellfish quality, a study was conducted in Brittany (France) over a period of 20 months. A hydrodynamic model was used to simulate wastewater impact on microbial water quality. To validate the model, wastewater from the three main sewage treatment plants and shellfish from three sites were sampled monthly. Bacterial indicators (E. coli), F-RNA phages were searched for by culture and noroviruses by RT-PCR and hybridisation. These microorganisms were detected in the three effluents and clams, with no marked seasonal variation. The microbial concentrations in the two oyster beds, distant from the effluent outfall, were low, and only three of the samples were positive for norovirus. For simulation, the winter wastewater inputs of E. coli and phages were calculated and an estimation for norovirus flux was made from the epidemic situation in the population. The microbial behaviour was included in the model by a decay-rate factor. Results from the model calculations were found to be very similar to E. coli and phage concentrations observed in shellfish. For noroviruses, the model indicated that shellfish distant from the wastewater input were under the detection limit of the RT-PCR method. This study demonstrated the use of modelisation to interpret norovirus contamination in various areas.