Diferenças sexuais no desenvolvimento de parkinsonismo induzido pelo tratamento repetido com reserpina
Data
2019
Autores
Lima, Alvaro da Costa [UNIFESP]
Orientadores
Silva, Regina Helena da [UNIFESP]
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A Doença de Parkinson (DP) é a segunda doença neurodegenerativa mais frequente na população idosa mundial. De relevância, diversos estudos mostram que há uma maior frequência de DP em homens. A principal sintomatologia da doença é motora, caracterizada por tremor em repouso, dificuldade na inicialização do movimento, entre outros. Entretanto, há sintomas não motores, como os déficits cognitivos, os quais podem preceder os sintomas motores. Muitos modelos são propostos com o intuito de mimetizar as características sintomatológicas e fisiopatológicas da DP. Entretanto, a maioria dos modelos propostos promovem comprometimento motor agudo, o que não está de acordo com a característica progressiva da doença, além de impedir o estudo dos sintomas não motores. Desta forma, o nosso grupo de pesquisa propôs uma adaptação do protocolo clássico de reserpina (fármaco depletor de monoaminas que promove déficits motores), utilizando doses baixas em um tratamento crônico. Tal esquema possibilita a caracterização da progressividade vista na doença, além de evidenciar déficits pré-motores. O modelo já demonstrou validade quanto a sintomatologia (de face) e fisiopatologia (de constructo) e mais recentemente, a validade farmacológica (preditiva). Paralelamente, os hormônios sexuais desempenham um papel importante no desenvolvimento do sistema nervoso central dos diferentes sexos. Entre as diferenças, pode-se citar que as fêmeas apresentam aumento na densidade de terminais sinápticos dopaminérgicos no estriado, além de alterações nas densidades do transportador dopaminérgico, entre outros. Tendo em vistas essas diferenças sexuais no desenvolvimento neurológico, e a diferença na incidência da doença de Parkinson entre os sexos, o objetivo geral do presente trabalho foi investigar possíveis diferenças sexuais comportamentais e neuronais nas alterações induzidas pelo tratamento repetido com baixas doses de reserpina. Ratos Wistar machos e fêmeas receberam 10 ou 15 aplicações de reserpina (0,1mg/kg) ou veículo em dias alternados. Ao longo do tratamento, houve o acompanhamento do ciclo estral, e a realização de testes motores e cognitivos (catalepsia, campo aberto, movimentos orais e reconhecimento de objeto). A eutanásia dos animais ocorreu 48 horas após a 10ª ou 15ª aplicação, obtendo-se soro para a quantificação de estrógeno e os encéfalos para realização de imunohistoquímica para tirosina hidroxilase. Nossos resultados mostraram, como esperado, um aumento da catalepsia, na quantidade de movimentos involuntários orais, e déficits cognitivos, além de diminuição na contagem de células positivas para tirosina hidroxilase nos machos tratados com reserpina. Entretanto, o efeito da reserpina mostrou-se atenuado no comportamento cataléptico nas fêmeas, não ocorrendo efeito da reserpina nos movimentos orais, na tarefa cognitiva, e na contagem celular neste sexo. Não houve influência detectável da fase do ciclo estral nos comportamentos nem nas ratas controle nem nas tratadas. Quanto à concentração de estrógeno, houve uma tendência das fêmeas tratadas com reserpina apresentarem níveis maiores desse hormônio, a qual tornou-se significativa quando a análise foi feita considerando as fases do ciclo. Porém, não foi encontrada correlação entre o nível de estrógeno e a intensidade das alterações motoras. Com isso, pode-se afirmar que as fêmeas apresentam resistência ao desenvolvimento de parkinsonismo induzido pela administração repetida de baixas doses de reserpina. Entretanto, nas nossas condições experimentais, não houve influência do perfil hormonal nessa resistência apresentada pelas fêmeas.
Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease. Studies show that PD is more frequent in men than women. The main symptoms of the disease are motor signs such as resting tremor, difficulty in initializing movements, among others. However, there are also nonmotor alterations, such as cognitive deficits, that can precede the motor symptoms. Most animal models of PD produce acute severe motor impairment, which is not in accordance with the progressive feature of the disease. In addition, the study of non-motor symptoms is limited by the motor impairment. Recently, our research group proposed an adaptation of the classic reserpine (a monoamine depleting agent that promotes motor deficits) protocol, using a low-dose chronic treatment. This scheme allows the evaluation of the progressivity of the disease and of the pre-motor deficits. This model has already shown face, construct and predictive validities. Sexual hormones play an important role in the neural development of different sexes. Among the differences, females present an increase in the density of dopaminergic synaptic terminals in the striatum, in addition to alterations in the densities of the dopaminergic transporter. Considering these sexual differences in neurological development, and the difference in the prevalence of PD, the aim of the present study was to investigate possible behavioral and neuronal differences in the effects of the repeated treatment with low doses of reserpine on male and female rats. Male and female Wistar rats received 10 or 15 injections of reserpine (0,1mg / kg) or vehicle, alternate days. Throughout the treatment, we followed-up the estrous cycle and conducted motor and cognitive assessments (catalepsy open field behavior, oral movements and object recognition test). The euthanasia of the animals occurred 48 hours after the 10th or 15th applications, with the collection of serum for the quantification of estrogen hormone and the brains for tyrosine hydroxylase immunohistochemistry assays. As expected, our results shown that reserpine increased catalepsy, increase in the number of involuntary oral movements, and cognitive deficits in males, as well as increase of tyrosine hydroxylase positive cells. However, the effect of reserpine was attenuated in females, with decreased cataleptic behavior, and no effect of reserpine on oral movements, the cognitive task and in the cell score. There was no detectable influence of the estrous cycle stage on behavior. Regarding estrogen levels, there was a tendency towards the increase of these levels in reserpine-treated females that became significant when the analysis was conducted considering the cycle phase. However, there was no correlation between hormone levels and motor alterations. In summary, our results show that female rats are resistant to the development of progressive parkinsonism induced by reserpine. However, under our experimental conditions, there was no influence of the hormonal profile in this resistance.
Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease. Studies show that PD is more frequent in men than women. The main symptoms of the disease are motor signs such as resting tremor, difficulty in initializing movements, among others. However, there are also nonmotor alterations, such as cognitive deficits, that can precede the motor symptoms. Most animal models of PD produce acute severe motor impairment, which is not in accordance with the progressive feature of the disease. In addition, the study of non-motor symptoms is limited by the motor impairment. Recently, our research group proposed an adaptation of the classic reserpine (a monoamine depleting agent that promotes motor deficits) protocol, using a low-dose chronic treatment. This scheme allows the evaluation of the progressivity of the disease and of the pre-motor deficits. This model has already shown face, construct and predictive validities. Sexual hormones play an important role in the neural development of different sexes. Among the differences, females present an increase in the density of dopaminergic synaptic terminals in the striatum, in addition to alterations in the densities of the dopaminergic transporter. Considering these sexual differences in neurological development, and the difference in the prevalence of PD, the aim of the present study was to investigate possible behavioral and neuronal differences in the effects of the repeated treatment with low doses of reserpine on male and female rats. Male and female Wistar rats received 10 or 15 injections of reserpine (0,1mg / kg) or vehicle, alternate days. Throughout the treatment, we followed-up the estrous cycle and conducted motor and cognitive assessments (catalepsy open field behavior, oral movements and object recognition test). The euthanasia of the animals occurred 48 hours after the 10th or 15th applications, with the collection of serum for the quantification of estrogen hormone and the brains for tyrosine hydroxylase immunohistochemistry assays. As expected, our results shown that reserpine increased catalepsy, increase in the number of involuntary oral movements, and cognitive deficits in males, as well as increase of tyrosine hydroxylase positive cells. However, the effect of reserpine was attenuated in females, with decreased cataleptic behavior, and no effect of reserpine on oral movements, the cognitive task and in the cell score. There was no detectable influence of the estrous cycle stage on behavior. Regarding estrogen levels, there was a tendency towards the increase of these levels in reserpine-treated females that became significant when the analysis was conducted considering the cycle phase. However, there was no correlation between hormone levels and motor alterations. In summary, our results show that female rats are resistant to the development of progressive parkinsonism induced by reserpine. However, under our experimental conditions, there was no influence of the hormonal profile in this resistance.
Descrição
Citação
LIMA, Alvaro da Costa. Diferenças sexuais no desenvolvimento de parkinsonismo induzido pelo tratamento repetido com reserpina. São Paulo, 2019. 84 f. Dissertação (Mestrado em Farmacologia) – Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, 2019.