Assessment of serotonergic system in formation of memory and learning / Avaliação do sistema serotonérgico na formação de memória e aprendizagem

Abstract We evaluated the involvement of the serotonergic system on memory formation and learning processes in healthy adults Wistar rats. Fifty-seven rats of 5 groups had one serotonergic nuclei damaged by an electric current. Electrolytic lesion was carried out using a continuous current of 2mA during two seconds by stereotactic surgery. Animals were submitted to learning and memory tests. Rats presented different responses in the memory tests depending on the serotonergic nucleus involved. Both explicit and implicit memory may be affected after lesion although some groups showed significant difference and others did not. A damage in the serotonergic nucleus was able to cause impairment in the memory of Wistar. The formation of implicit and explicit memory is impaired after injury in some serotonergic nuclei.

Resumo Avaliar a participação do sistema serotoninérgico em processos de formação de memória e aprendizagem em ratos Wistar adultos saudáveis. Cinquenta e sete ratos de 5 grupos tinham um núcleo serotoninérgico danificado por uma corrente elétrica. A lesão eletrolítica foi realizada utilizando uma corrente contínua de 2 mA durante dois segundos por cirurgia estereotáxica. Os animais foram submetidos a testes de aprendizagem e memória. Os ratos apresentaram respostas diferentes nos testes de memória, dependendo do núcleo serotoninérgica envolvido. A memória explícita e implícita pode ser afetada após a lesão, embora alguns grupos apresentaram diferença significativa e outros não. A lesão no núcleo serotoninérgico foi capaz de causar danos na memória de Wistar. A formação da memória implícita e explícita é prejudicada após a lesão em alguns núcleos serotoninérgicos.

Potential impacts of climate variability on Dengue Hemorrhagic Fever in Honduras, 2010

Climate change and variability are affecting human health and disease direct or indirectly through many mechanisms. Dengue is one of those diseases that is strongly influenced by climate variability; however its study in Central America has been poorly approached. In this study, we assessed potential associations between macroclimatic and microclimatic variation and dengue hemorrhagic fever (DHF) cases in the main hospital of Honduras during 2010. In this year, 3,353 cases of DHF were reported in the Hospital Escuela, Tegucigalpa. Climatic periods marked a difference of 158% in the mean incidence of cases, from El Niño weeks (-99% of cases below the mean incidence) to La Niña months (+59% of cases above it) (p<0.01). Linear regression showed significantly higher dengue incidence with lower values of Oceanic Niño Index (p=0.0097), higher rain probability (p=0.0149), accumulated rain (p=0.0443) and higher relative humidity (p=0.0292). At a multiple linear regression model using those variables, ONI values shown to be the most important and significant factor found to be associated with the monthly occurrence of DHF cases (r2=0.649; βstandardized=–0.836; p=0.01). As has been shown herein, climate variability is an important element influencing the dengue epidemiology in Honduras. However, it is necessary to extend these studies in this and other countries in the Central America region, because these models can be applied for surveillance as well as for prediction of dengue.