EFEITOS DE BLOQUEADORES DA RECAPTAÇÃO DE NEUROTRANSMISSORES MONOAMINÉRGICOS NOS SINTOMAS NÃO-MOTORES DA DOENÇA DE PARKINSON INDUZIDA POR 6-OHDA EM RATOS

Abstract

Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease. Depression and anxiety are common psychological disorders in patients suffering from PD. In the literature, there is much discussion about the probable mechanism leading to depression in PD and if it is associated with other psychiatric symptoms such as anxiety. It is still unclear which neurotransmitters and which neural pathways alterations could be related to the development of these non-motor symptoms. This study aimed to test how distinct monoamine neurotransmitters reuptake inhibitors interfere in the behavioral changes caused by damage to the nigrostriatal pathway with 6-OHDA in rats. To test this hypothesis, animals were subjected to stereotaxic surgery for infusion of 6-OHDA into their medial forebrain bundle (MFB) or their substantia nigra compacta (SN). These animals were divided in groups, one receiving bupropion (dopamine uptake blocker), fluoxetine (serotonin uptake blocker) or nortriptylin (noradrenalin uptake blocker), apart from a 6-OHDA with no blockers and a control group, which received 0,9% saline solution instead of 6-OHDA. At day 21 after surgery, behavioral testing started. Locomotor activity was evaluated by the open field test; depressive-like behavior by the forced swimming and the sucrose preference tests; and anxious behavior by the elevated plus maze test. The results were analyzed by one-way ANOVA, followed by post hoc Newman-Keuls post hoc test. The injury provoked by the infusion of the toxin in the SN was able to cause non-motor symptoms of PD, such as depression and anxiety, with no presentation of motor impairment by the animals, while injury in the FPM didn’t cause the same symptoms. On the SN lesioned animals, the administration of nortryptiline and bupropion were able to prevent from the 6-OHDA effect on the time spent on the open arm of the elevated plus maze test. On the same animals, bupropion, nortriptyline and fluoxetine were capable of prevent the reduction of the number of entrances to the center and the open arms of the same maze, and the reduction of swimming time and increase of immobility time caused by 6-OHDA on the forced swimming test. These data indicate that the SN lesion causes more behavior alteration than the MFB lesion in rats, also demonstrating that these motor alterations depend on the effect of the toxin on dopaminergic, noradrenergic and serotoninergic neurons. This contributes to the characterization of this model of behavioral alterations related to the nigrostriatal lesion.