The effects of long-term dopaminergic treatment on locomotor behavior in rats

Abstract

Long-term treatments with dopaminergic agents are associated with adverse effects, including augmentation. Augmentation consists of an exacerbation of restless legs syndrome (a sleep-related movement disorder) symptoms during treatment compared to those experienced during the period before therapy was initiated. The objective of this study was to examine locomotor activity in rats after long-term dopaminergic treatment and its relationship with expression of the D2 receptor, in addition to demonstrating possible evidence of augmentation. The rats were divided into control (CTRL) and drug (Pramipexole—PPX) groups that received daily saline vehicle and PPX treatments, respectively, for 71 days. The locomotor behavior of the animals was evaluated weekly in the Open Field test for 71 days. The expression of the dopamine D2 receptor was evaluated by Western Blot analysis. The animals that received the PPX demonstrated a significant reduction in locomotor activity from day 1 to day 57 and a significant increase in immobility time from day 1 to day 64 relative to baseline values, but these values had returned to baseline levels at 71 days. No changes in the expression of the D2 receptor were demonstrated after treatment with a dopaminergic agonist. This study suggests changes in locomotor activity in rats after long-term PPX treatment that include an immediate reduction of locomotion and an increase in immobilization, and after 64 days, these values returned to baseline levels without evidence of augmentation. In addition, it was not possible to demonstrate a relationship between locomotor activity and the expression of D2 receptors under these conditions.

5-Aza-2’-deoxycytidine in the medial prefrontal cortex regulates alcohol-related behavior and Ntf3-TrkC expression in rats

“…The OFT is commonly used to assess the sedative, toxic, or stimulant effects of compounds [ 30 , 31 ]. The duration of time spent and the measured activity in the central zone likely gage some aspects of emotionality-like behavior, including anxiety and exploratory drive [ 32 – 34 ].…”

Investigation of the behavioral and neurochemical effects of monosodium glutamate on neonatal rats

“…grooming values and a decrease in rearing values were also observed. Studies by Oliveira de Almeida et al (30) were the first to report that the animal became more hypoactive and also rooming number increased after MSG injections. They evaluated the expression of dopamine D2 receptor via western blot analysis and implemented an open field test on day 57 of their experiment on rats.…”

“…GABA is emitted in the brain due to the dopamine level (34). Oliveira de Almeida et al (30) examined the effect of dopaminergic increase on the locomotor activity of rats and its relation with the expression of dopamine D2 receptor. They argued that the increased expression of dopamine receptor D1 compared to the receptor D2 reduced the locomotor activity and thus caused a decrease in mobilization.…”