Validação farmacológica de um modelo animal progressivo para a doença de Parkinson induzido por reserpina
Arquivos
Data
2022-02-02
Autores
Bioni, Vinicius dos Santos 
Orientadores
Silva, Regina Helena
Tipo
Dissertação de mestrado
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Resumo
A Doença de Parkinson (DP) é um distúrbio motor que atualmente acomete de 1-2% da população mundial acima dos 60 anos, configurando-se como a segunda doença neurodegenerativa mais frequente em todo o mundo. Validamos alterações neuroquímicas e comportamentais para um modelo progressivo da DP através da administração repetida de baixas doses de reserpina (0.1 mg/kg, em dias alternados). Dentre as alterações comportamentais encontradas temos o aumento progressivo na latência para o início de um movimento e discinesias orais, assim como redução da atividade motora geral. Estas, por sua vez, também são acompanhadas de alterações neuroquímicas progressivas e compatíveis com a fisiopatologia da DP, como a redução da expressão da tirosina hidroxilase e conteúdo de dopamina, e o aumento da expressão de alfa-sinucleína e estresse oxidativo no SNC. No entanto, ainda é necessário validá-lo para o principal tratamento sintomático clássico da DP, a reposição dopaminérgica com L-DOPA. Sendo assim, este estudo avaliou os efeitos agudos e crônicos da L-DOPA sobre a recuperação de parâmetros motores no modelo progressivo da DP induzido por administrações repetidas de reserpina.
Camundongos Suíços machos, com 6 meses de idade, foram submetidos a 20 injeções de reserpina, na dose de 0,1mg/kg, em dias alternados durante 40 dias. Tratamento agudo de L-DOPA foi unicamente realizado 48h após a última injeção de reserpina, nas doses de 25, 50, 100 e 200mg/kg, e então observado o padrão comportamental dos animais. A partir dos resultados do tratamento agudo, definimos duas doses, 50 e 100mg/kg, para o tratamento crônico diário ao longo dos 40 dias de experimento. Foram realizados testes de catalepsia, campo aberto e movimentos orais em ambos os tratamentos, e foi coletado material dos animais do tratamento crônico para avaliação neuroquímica.
Os resultados mostraram um aumento do comportamento de catalepsia induzido pela reserpina. O tratamento agudo com L-DOPA foi eficaz em diminuir o tempo do comportamento de catalepsia nas maiores doses, já o tratamento crônico foi capaz de retardar e por momentos impedir o aumento da catalepsia. No campo aberto foi observado diminuição da locomoção geral pela administração de reserpina, novamente a maior dose aguda de L-DOPA foi capaz de reverter o efeito da reserpina, já no crônico, a menor dose intensificou o efeito da reserpina. O comportamento de mastigação direcionada ao vácuo foi aumentado com a administração de reserpina, e revertido parcialmente apenas na dose aguda de 50mg/kg e ambas as crônicas foram capazes de reduzir a frequência do comportamento. A avaliação neuroquímica apontou diminuição dos níveis de dopamina no estriado após administração crônica de reserpina, e o tratamento crônico com L-DOPA aumentou parcialmente os níveis dopaminérgicos estriatais.
Em geral, confirmamos a capacidade da reserpina induzir comportamentos equivalentes aos vistos na clínica, e acarretar depleção dopaminérgica na via mais abordada na DP. Ainda, o tratamento com L-DOPA foi capaz de reduzir os efeitos promovidos pela reserpina. Esses resultados, juntamente com evidências prévias, reforçam a validade do protocolo de administração repetida de uma dose baixa de reserpina em roedores como um modelo adequado para o estudo da doença de Parkinson.
Parkinson’s disease is a motor disturbance which affects 1-2% of world’s population over 60 years old, staging as the second most frequent neurodegenerative disease. Repetitive low-dose reserpine progressive model of Parkinson’s disease (0.1mg/kg, every each day) had neurochemical and behavioral alterations validated. Progressive increased latency to start movement and oral dyskinesia, together with general decrease of motor activity resumes behavioral alterations. Progressive neurochemical alterations compatible to Parkinson’s disease physiopathology, such as decrement in tyrosine hydroxylase expression, dopamine content reduction, and increased alpha-synuclein expression and oxidative stress on CNS are also detected under this proposed protocol. Nonetheless, the pharmacological validation to the gold standard symptomatic treatment, L-DOPA dopaminergic reposition, is still a gap to complete the validation of the progressive reserpine model. Thus, this study evaluated acute and chronic effects of L-DOPA treatment on motor and neurochemical parameters on the progressive animal model of Parkinson’s disease induced by repeated administration of reserpine. Swiss male mice, 6 months of age, were submitted to 20 0.1mg/kg reserpine injections, every other day for 40 days. Acute L-DOPA treatment was given 48h after the last reserpine injection, at 25, 50, 100 and 200mg/kg doses, then behavioral tests were assessed. After the analysis of the results of the acute experiment, the 50 and 100mg/kg doses were chosen for daily chronic 40 days L-DOPA treatment. Catalepsy test, open field test and oral movements evaluation were performed for both treatments, and brains were collected for neurochemical evaluation after chronic treatment. Results showed increased catalepsy behavior induced by reserpine administration. Acute L-DOPA treatment was able to decrease time on the bar on higher doses. Furthermore, chronic treatment delayed and even prevented catalepsy increasement at some time points. Open field test revealed general locomotion impairment after reserpine administration, higher acute L-DOPA dose was capable to revert reserpine effect. Chronic administration of the lower dose on the other hand aggravated reserpine effect. Vacuous chewing behavior increasement was observed after reserpine administration and attenuated only xiii by 50mg/kg acute L-DOPA dose, and both doses on chronic regimen. Neurochemical assessment appointed diminished levels of dopamine after chronic administration of reserpine, and chronic treatment with L-DOPA was capable to partially reverse dopaminergic depletion. In general, we confirmed reserpine capacity to induce equivalent behaviors seen in clinic, and lead to dopaminergic depletion on the most studied neuronal pathway related to PD. Additionally, L-DOPA treatment was capable to attenuate or even reverse effects induced by reserpine. These results, together with previous evidence, support the validity of the protocol of low-dose repeated treatment in rodent as an adequate model for the study of Parkinson’s disease.
Parkinson’s disease is a motor disturbance which affects 1-2% of world’s population over 60 years old, staging as the second most frequent neurodegenerative disease. Repetitive low-dose reserpine progressive model of Parkinson’s disease (0.1mg/kg, every each day) had neurochemical and behavioral alterations validated. Progressive increased latency to start movement and oral dyskinesia, together with general decrease of motor activity resumes behavioral alterations. Progressive neurochemical alterations compatible to Parkinson’s disease physiopathology, such as decrement in tyrosine hydroxylase expression, dopamine content reduction, and increased alpha-synuclein expression and oxidative stress on CNS are also detected under this proposed protocol. Nonetheless, the pharmacological validation to the gold standard symptomatic treatment, L-DOPA dopaminergic reposition, is still a gap to complete the validation of the progressive reserpine model. Thus, this study evaluated acute and chronic effects of L-DOPA treatment on motor and neurochemical parameters on the progressive animal model of Parkinson’s disease induced by repeated administration of reserpine. Swiss male mice, 6 months of age, were submitted to 20 0.1mg/kg reserpine injections, every other day for 40 days. Acute L-DOPA treatment was given 48h after the last reserpine injection, at 25, 50, 100 and 200mg/kg doses, then behavioral tests were assessed. After the analysis of the results of the acute experiment, the 50 and 100mg/kg doses were chosen for daily chronic 40 days L-DOPA treatment. Catalepsy test, open field test and oral movements evaluation were performed for both treatments, and brains were collected for neurochemical evaluation after chronic treatment. Results showed increased catalepsy behavior induced by reserpine administration. Acute L-DOPA treatment was able to decrease time on the bar on higher doses. Furthermore, chronic treatment delayed and even prevented catalepsy increasement at some time points. Open field test revealed general locomotion impairment after reserpine administration, higher acute L-DOPA dose was capable to revert reserpine effect. Chronic administration of the lower dose on the other hand aggravated reserpine effect. Vacuous chewing behavior increasement was observed after reserpine administration and attenuated only xiii by 50mg/kg acute L-DOPA dose, and both doses on chronic regimen. Neurochemical assessment appointed diminished levels of dopamine after chronic administration of reserpine, and chronic treatment with L-DOPA was capable to partially reverse dopaminergic depletion. In general, we confirmed reserpine capacity to induce equivalent behaviors seen in clinic, and lead to dopaminergic depletion on the most studied neuronal pathway related to PD. Additionally, L-DOPA treatment was capable to attenuate or even reverse effects induced by reserpine. These results, together with previous evidence, support the validity of the protocol of low-dose repeated treatment in rodent as an adequate model for the study of Parkinson’s disease.