Avaliação do aprendizado dependente de estado induzido por psicofármacos em ratas
Data
2023-03-03
Autores
Santos, Murilo Américo de Paiva 
Orientadores
Silva, Regina Helena da
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A aprendizagem é uma propriedade fundamental do cérebro humano, por meio da
qual adquirimos informações e conhecimentos que podem ser armazenados, ou seja,
memorizados. Sabe-se que a memória é modulada por vários fatores internos e
externos, como o estado emocional, a influência de substâncias ou fármacos, ou ainda
pelo ambiente. O aprendizado dependente de estado (ADE) é um fenômeno que
ocorre quando é necessário que o indivíduo esteja no mesmo estado em que estava
quando adquiria determinada informação para que o mesmo a evoque. Embora o ADE
tenha sido descrito para diversos tipos de manipulações em humanos e modelos
animais, o efeito de psicofármacos nesse processo é o mais bem caracterizado.
Nesse sentido, o ADE tem sido sugerido como um importante mecanismo envolvido
no uso abusivo e dependência de algumas substâncias ou fármacos. Porém, a maioria
dos estudos em animais, se não todos, investiga tal fenômeno apenas em animais
machos. O objetivo deste trabalho foi investigar o ADE induzido pelas principais
classes de psicofármacos relacionadas ao transtorno por uso de substâncias (etanol,
benzodiazepínicos, psicoestimulantes e opioides) em ratos machos e fêmeas. Além
disso, foi investigada a possível influência da fase do ciclo hormonal feminino durante
a evocação no ADE. Para isso, utilizamos a esquiva discriminativa em labirinto em
cruz elevado, que vem sendo aplicada para estudar o ADE em roedores machos, e
apresenta a vantagem de poder-se investigar os níveis emocionais e a atividade
motora (fenômenos comumente alterados por psicofármacos) concomitantemente ao
aprendizado e memória. Foram utilizadas 200 ratas e 129 ratos da linhagem Wistar,
com 3 meses de idade, provenientes do Biotério Central da Universidade Federal de
São Paulo. Foram utilizadas as seguintes substâncias: etanol (1,8 g/Kg) diazepam (2
mg/kg), anfetamina (3 mg/Kg) e morfina (10 mg/kg), uma em cada um dos quatro
experimentos realizados. Em cada experimento, após a administração de cada
fármaco (diluído em salina) ou veículo os animais foram submetidos à sessão de treino
na EDL (para avaliação do aprendizado, do comportamento tipo ansioso e da
locomoção), e o mesmo procedimento se repetiu no dia do teste, onde foi aplicado
novamente o fármaco ou veículo. Após a saída do aparato comportamental na fase
de teste, foi realizado o procedimento de lavagem vaginal para avaliação da fase do
ciclo estral em que a rata se encontrava. De maneira geral, a morfina promoveu um
déficit na tarefa de EDL em ambos os sexos, sem evidência da influência do ADE.
Além disso, alguns parâmetros indicaram um possível efeito ansiogênico desse
fármaco nas fêmeas, o que pode ter influenciado sua ação na memória. O diazepam
promoveu um déficit de evocação nas fêmeas quando administrado antes do teste e
esse efeito também não pareceu envolver o ADE. O efeito do etanol sobre a memória
das fêmeas foi influenciado pelo ADE, já que o déficit promovido pela administração
antes do treino foi revertido pela administração pré-teste neste sexo. Ao contrário do
observado para o etanol, o efeito da anfetamina na memória foi influenciado pelo ADE
apenas em machos. Em linhas gerais, ratas em proestro/estro apresentam
desempenho melhor na discriminação entre os braços fechados comparadas às ratas em metaestro/diestro, mas a fase do ciclo não pareceu influenciar o efeito dos
fármacos. Em conclusão, nossa pesquisa mostrou que machos e fêmeas controles
apresentaram bom desempenho na tarefa, e que em alguns casos houve alteração
induzida pelos fármacos com influência do fenômeno do ADE, sem similaridade entre
os sexos. Esses resultados reforçam a relevância da realização de estudos sobre
efeitos comportamentais de psicofármacos serem realizados em ambos os sexos
Learning is a key property of the human brain, which allow us to acquire information and knowledge that can be stored and retrieved. There is evidence that memory is modulated by several internal and external factors, such as emotional state, influence of substances or drugs, or even environmental features. State-dependent learning (ADE) is a phenomenon that occurs when it is necessary for the individual to be in the same state he was in when acquiring certain information in order to retrieve it. Although ADE has been described for different types of manipulations in humans and animal models, the effect of psychotropic drugs in this process is the most studied. In this sense, ADE has been suggested as an important mechanism involved in compulsive use and dependence of some substances or drugs. Nevertheless, most, if not all, animal studies on the subject have been conducted with male rodents. The aim of this work was to investigate ADE induced by the main classes of psychotropic drugs related to substance use disorder (ethanol, benzodiazepines, psychostimulants, and opioids) in male and female rats. In addition, the possible participation of the female hormonal cycle phase during retrieval was investigated. We used the plus-maze discriminative avoidance task (EDL), which has been widely applied to study ADE in male rodents and has the advantage of allowing the investigation of emotional levels and motor activity (phenomena commonly altered by psychotropic drugs) concurrently with learning and memory. Two hundred female and 129 male Wistar rats aged 3 months, from the Central Animal Facility of the Federal University of São Paulo were used. Ethanol (1.8 g/Kg) diazepam (2 mg/kg), amphetamine (3 mg/Kg) and morphine (10 mg/kg) were used, one in each of the four experiments that were carried out. In each experiment, after the administration of the drug (diluted in saline) or vehicle, the animals were submitted to a training session in the EDL (to assess learning, anxietylike behavior, and locomotion), and the same procedure was repeated on the day of the test, where the drug or vehicle was applied again. After leaving the behavioral apparatus in the test phase, the vaginal lavage procedure was performed to assess the phase of the estrous cycle. In general, morphine promoted a deficit in the EDL in both sexes, without evidence of the influence of ADE. In addition, some parameters indicated a possible anxiogenic effect in females, which may have influenced the action of this drug on memory. Diazepam promoted a retrieval deficit in females when administered before the test and this effect also did not seem to involve ADE. The effect of ethanol on female memory was influenced by ADE, since the deficit promoted by pre-training administration was reversed by pre-test administration of the drug in this sex. Contrary to what was observed for ethanol, the effect of amphetamine on memory was influenced by ADE only in males. In general terms, rats in proestrus/estrus present better performance in the discrimination between closed arms compared to rats in metestrus/diestrus, but the phase of the cycle did not seem to influence the effect of the drugs. In conclusion, our research showed that male and female rats of control groups performed well on the task, and that in some cases there were drug-induced alterations with influence of the ADE phenomenon, but with differences between sexes. These results reinforce the relevance of performing behavioral studies to investigate drug effects in both sexes.
Learning is a key property of the human brain, which allow us to acquire information and knowledge that can be stored and retrieved. There is evidence that memory is modulated by several internal and external factors, such as emotional state, influence of substances or drugs, or even environmental features. State-dependent learning (ADE) is a phenomenon that occurs when it is necessary for the individual to be in the same state he was in when acquiring certain information in order to retrieve it. Although ADE has been described for different types of manipulations in humans and animal models, the effect of psychotropic drugs in this process is the most studied. In this sense, ADE has been suggested as an important mechanism involved in compulsive use and dependence of some substances or drugs. Nevertheless, most, if not all, animal studies on the subject have been conducted with male rodents. The aim of this work was to investigate ADE induced by the main classes of psychotropic drugs related to substance use disorder (ethanol, benzodiazepines, psychostimulants, and opioids) in male and female rats. In addition, the possible participation of the female hormonal cycle phase during retrieval was investigated. We used the plus-maze discriminative avoidance task (EDL), which has been widely applied to study ADE in male rodents and has the advantage of allowing the investigation of emotional levels and motor activity (phenomena commonly altered by psychotropic drugs) concurrently with learning and memory. Two hundred female and 129 male Wistar rats aged 3 months, from the Central Animal Facility of the Federal University of São Paulo were used. Ethanol (1.8 g/Kg) diazepam (2 mg/kg), amphetamine (3 mg/Kg) and morphine (10 mg/kg) were used, one in each of the four experiments that were carried out. In each experiment, after the administration of the drug (diluted in saline) or vehicle, the animals were submitted to a training session in the EDL (to assess learning, anxietylike behavior, and locomotion), and the same procedure was repeated on the day of the test, where the drug or vehicle was applied again. After leaving the behavioral apparatus in the test phase, the vaginal lavage procedure was performed to assess the phase of the estrous cycle. In general, morphine promoted a deficit in the EDL in both sexes, without evidence of the influence of ADE. In addition, some parameters indicated a possible anxiogenic effect in females, which may have influenced the action of this drug on memory. Diazepam promoted a retrieval deficit in females when administered before the test and this effect also did not seem to involve ADE. The effect of ethanol on female memory was influenced by ADE, since the deficit promoted by pre-training administration was reversed by pre-test administration of the drug in this sex. Contrary to what was observed for ethanol, the effect of amphetamine on memory was influenced by ADE only in males. In general terms, rats in proestrus/estrus present better performance in the discrimination between closed arms compared to rats in metestrus/diestrus, but the phase of the cycle did not seem to influence the effect of the drugs. In conclusion, our research showed that male and female rats of control groups performed well on the task, and that in some cases there were drug-induced alterations with influence of the ADE phenomenon, but with differences between sexes. These results reinforce the relevance of performing behavioral studies to investigate drug effects in both sexes.
Descrição
Citação
SANTOS, Murilo Américo de Paiva. Avaliação do aprendizado dependente de estado induzido por psicofármacos em ratas. 2023. 154 f. Tese (Doutorado em Farmacologia) – Escola Paulista de Medicina, Universidade Federal de São Paulo (UNIFESP). São Paulo, 2023.