Page 109 - AN-3-4

Advanced Neurology Stress accelerates parkinsonism in rats

increased levels of inflammatory factors (such as increased – 23°C), free access to food and water, and light/dark cycle
astroglia activation and production of inflammatory of 12/12 h (lights on at 6:30 am). The animals were handled
cytokines), reduced proportion of tyrosine hydroxylase– for a period of 5 min daily during the 14-day period before
positive cells in the SNpc, and augmented immunostaining the beginning of the experiment to habituate them to the
for α-synuclein. 27-30 This progressive protocol has the experimenter. All experiments were conducted during the
advantage of gradually promoting motor impairments light phase and by researchers blinded to the treatment and
in rodents, which has been shown to be bidirectionally stress protocol.
modified by pharmacological and non-pharmacological Stressors (as listed in Table 1) were applied 6 days
interventions. 31-36 weekly. In Experiment II, the animals were subjected to

Considering the abovementioned findings, the present the UMS protocol for 1 week (days 1 – 7). The duration
study aimed to investigate the effects of unpredictable of exposure to the UMS protocol in Experiment II was
mild stress (UMS) on the onset and progression of determined based on the results of Experiment I. After the
repeated reserpine-induced parkinsonism in Wistar UMS protocol, treatment with either vehicle or reserpine
rats. Furthermore, this study examined the effect of (0.1 mg/kg) was performed from days 9 to 29. Catalepsy
UMS on brain oxidative stress (evaluated by membrane tests were conducted every 3 days from days 8 to 29, and
lipid peroxidation assay) and plasma CORT levels of the open field test was performed twice, on days 19 and
rats subjected to the protocol of repeated reserpine 29. On day 31, 48 h after the last injection of vehicle or
administration. reserpine, the animals were euthanized via decapitation,
without anesthesia, and blood samples were collected for
2. Methods the determination of plasma CORT levels. Moreover, the
2.1. Animals, general procedures, and experimental striatum was dissected and stored for lipid peroxidation
design assay. Figure 1 provides a summary of the experimental
design.
This study was approved by the Ethics Committee of
Universidade Federal de São Paulo (protocol 1365020516), 2.2. UMS protocol
and all procedures were conducted in accordance with The rats that were subjected to the UMS protocol were
the Brazilian legislation for the use of animals in scientific placed in a separate room from the control groups
research (Law Number 11,794). A total of 76 6-month- throughout the study. This procedure was implemented
old male Wistar rats were used in the experiments to prevent changes in the behavior of the control rats due
(Experiment I: n = 36 and Experiment II: n = 40). Groups to possible alert ultrasonic vocalization from the stressed
of 4 – 5 animals were housed in polypropylene plastic rats. The stress procedures were performed daily from
37
cages measuring 33 × 40 × 17 cm and placed under the Sunday to Friday, each lasting 12 h, with no procedures
following conditions: controlled airflow, acoustic isolation, conducted on Saturdays. The stressors used in the protocol
temperature (22°C ± 1°C), and a 12/12-h light/dark cycle are listed in Table 1.
(lights on at 7:30 am). All efforts were made to minimize
animal pain or discomfort. 2.3. Drug treatment
In Experiment I, the animals were randomly categorized Reserpine (Sigma Chemical Co., St. Louis, MO, USA) was
into four groups; three groups were subjected to the UMS dissolved in 1% glacial acetic acid and diluted with distilled
protocol for different durations (1, 2, or 3 weeks), and the water to the correct concentration (0.1 mg/mL). The
remaining group was not subjected to the UMS protocol vehicle consisted of the same concentration of acetic acid
(control group). as in the reserpine solution and water. Either the vehicle
In Experiment II, the rats were randomly assigned to or 0.1 mg/kg reserpine was injected subcutaneously every
one of four experimental groups, namely, control-vehicle other day, in a total of 10 injections.
(Ctl-Veh, treated with vehicle only), control-reserpine
(Ctl-Res, treated with reserpine only), stress-vehicle
(St-Veh, animals subjected to the UMS protocol and
treated with vehicle), and stress-reserpine (St-Res, animals
subjected to the UMS protocol and treated with reserpine).
Rats subjected to the UMS protocol were housed in a
different room compared with those in the control groups.
The control groups were placed under the following Figure 1. Schematic of the experimental design (Experiment II)
conditions: controlled ventilation and temperature (20°C Abbreviation: UMS: Unpredictable mild stress.

Volume 3 Issue 4 (2024) 3 doi: 10.36922/an.4037