Serotonergic dysfunction in a model of parkinsonism induced by reserpine

Evaluating the Neuroprotective Potential of Novel Benzodioxole Derivatives in Parkinson's Disease via AMPA Receptor Modulation

Parkinson's disease (PD) is a significant health issue because it gradually damages the nervous system. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors play a significant role in the development of PD. The current investigation employed hybrid benzodioxole-propanamide (BDZ-P) compounds to get information on AMPA receptors, analyze their biochemical and biophysical properties, and assess their neuroprotective effects. Examining the biophysical characteristics of all the subunits of the AMPA receptor offers insights into the impact of BDZ-P on the desensitization and deactivation rate. It demonstrates a partial improvement in the locomotor capacities in a mouse model of Parkinson's disease. In addition, the in vivo experiment assessed the locomotor activity by utilizing the open-field test. Our findings demonstrated that BDZ-P7 stands out with its remarkable potency, inhibiting the GluA2 subunit nearly 8-fold with an IC50 of 3.03 μM, GluA1/2 by 7.5-fold with an IC50 of 3.14 μM, GluA2/3 by nearly 7-fold with an IC50 of 3.19 μM, and GluA1 by 6.5-fold with an IC50 of 3.2 μM, significantly impacting the desensitization and deactivation rate of the AMPA receptor. BDZ-P7 showed an in vivo impact of partially reinstating locomotor abilities in a mouse model of PD. The results above suggest that the BDZ-P7 compounds show great promise as top contenders for the development of novel neuroprotective therapies.

Translating Pathological Brain Activity Primers in Parkinson's Disease Research

Translational experimental approaches that help us better trace Parkinson's disease (PD) pathophysiological mechanisms leading to new therapeutic targets are urgently needed. In this article, we review recent experimental and clinical studies addressing abnormal neuronal activity and pathological network oscillations, as well as their underlying mechanisms and modulation. Our aim is to enhance our knowledge about the progression of Parkinson's disease pathology and the timing of its symptom's manifestation. Here, we present mechanistic insights relevant for the generation of aberrant oscillatory activity within the cortico-basal ganglia circuits. We summarize recent achievements extrapolated from available PD animal models, discuss their advantages and limitations, debate on their differential applicability, and suggest approaches for transferring knowledge on disease pathology into future research and clinical applications.

Cannabinoids and the endocannabinoid system in fibromyalgia: A review of preclinical and clinical research

Characterised by chronic widespread musculoskeletal pain, generalised hyperalgesia, and psychological distress, fibromyalgia (FM) is a significant unmet clinical need. The endogenous cannabinoid system plays an important role in modulating both pain and the stress response. Here, we appraise the evidence, from preclinical and clinical studies, for a role of the endocannabinoid system in FM and the therapeutic potential of targeting the endocannabinoid system. While many animal models have been used to study FM, the reserpine-induced myalgia model has emerged as perhaps the most translatable to the clinical phenotype. Inhibition of fatty acid amide hydrolase (FAAH) has shown promise in preclinical studies, ameliorating pain- and anxiety-related behaviour . Clinically, there is evidence for alterations in the endocannabinoid system in patients with FM, including single nucleotide polymorphisms and increased levels of circulating endocannabinoids and related N-acylethanolamines. Single entity cannabinoids, cannabis, and cannabis-based medicines in patients with FM show promise therapeutically but limitations in methodology and lack of longitudinal studies to assess efficacy and tolerability preclude the current recommendation for their use in patients with FM. Gaps in the literature that warrant further investigation are discussed, particularly the need for further development of animal models with high validity for the multifaceted nature of FM, balanced studies to eliminate sex-bias in preclinical research, and ultimately, better translation between preclinical and clinical research.

Antiperspirant effects and mechanism investigation of Mulisan decoction in rats based on plasma metabolomics

CONTEXT

Mulisan decoction (MLS) is a classic formula of traditional Chinese medicine for treating hyperhidrosis. The mechanism remains unclear.

OBJECTIVE

To investigate the antiperspirant effect and underlying mechanisms of MLS.

MATERIALS AND METHODS

Fifty rats were divided into control, model, and three doses of MLS intervention groups (n = 10). Rats except for control group were induced diseases features of the applicable scope of MLS via i.p. reserpine (0.5 mg/kg/d) for 10 days. From day 11, MLS groups were administrated orally MLS at 0.6, 3, and 15 g/kg once a day for 14 days, respectively. After the last administration, sweating was induced in all rats via s.c. pilocarpine (25 mg/kg), the right hind foot of rats was stained, and sweat point numbers were observed. Rat serum was collected to detect IL-2, IL-6, IFN-γ, and TNF-α. Rat plasma was collected for endogenous metabolite analysis via UPLC-QE-Focus-MS.

RESULTS

Rats treated with MLS presented a significant decrease in sweat point numbers (13.5%), increase in body weight (13.2%), and promotion in the balance of Th1/Th2 cytokine ratio via increasing IL-2 (38.3%), IFN-γ (20.1%), and TNF-α (22.0%) and decreasing IL-6 (24.7%) compared with the model group (p < 0.05). Plasma metabolomics disclosed 15 potential biomarkers related to model rats, of which two could be significantly reversed by MLS (p < 0.05). The involved pathways were pantothenate and CoA biosynthesis, and porphyrin metabolism.

CONCLUSIONS

MLS demonstrated a good antiperspirant effect and metabolism improvement. These findings inspire more clinical study validation on immune improvement and antiperspirant effect.

Lycium barbarum polysaccharide improves dopamine metabolism and symptoms in an MPTP-induced model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease in middle-aged and elderly populations, whereas there is no cure for PD so far. Novel animal models and medications await development to elucidate the aetiology of PD and attenuate the symptoms, respectively.

METHODS

A neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), was used in the current study to establish a PD pathologic model in silkworms. The time required to complete specific behaviours was recorded. Dopamine content was detected by ultra-performance liquid chromatography (UPLC). The activity of insect tyrosine hydroxylase (TH) was determined using a double-antibody sandwich method. Oxidative stress was assessed by changes in antioxidant enzyme activity and the content of oxidative products.

RESULTS

MPTP-treated silkworms were characterized by impaired motor ability, reduced dopamine content, and elevated oxidative stress level. The expression of TH, a dopamine biosynthetic enzyme within dopaminergic neurons in the brain, was significantly reduced, indicating that dopaminergic neurons were damaged. Moreover, MPTP-induced motility impairment and reduced dopamine level in the silkworm PD model could be rescued after feeding a combination of levodopa (L-dopa [LD]) and carbidopa (CD). MPTP-induced oxidative damage was also alleviated, in ways consistent with other PD animal models. Interestingly, administration of Lycium barbarum polysaccharide (LBP) improved the motor ability, dopamine level, and TH activity, and the oxidative damage was concomitantly reduced in the silkworm PD model.

CONCLUSIONS

This study provides a promising animal model for elucidating the pathogenesis of PD, as well as a relevant preliminary drug screening (e.g., LBP) and evaluation.

Aging accentuates decrease in tyrosine hydroxylase immunoreactivity associated with the increase in the motor impairment in a model of reserpine-induced parkinsonism

Parkinson's disease (PD) is an age-related neurodegenerative disorder characterized by progressive dopaminergic neuron loss. Animal models have been used to develop a better understanding of the pathophysiologic mechanisms of PD. However, these models are usually conducted with young animals diverging of the age of PD patients, suggesting a bias in translational science. Thus, the aim of the study was to evaluate the effect of the age on rats in a progressive parkinsonism model induced by reserpine (RES). Adult (6 - 8 month-old) or elderly (18 - 24 month-old) male rats were assigned to six groups: control-elderly (CTL-ELDERLY), reserpine-elderly (RES-ELDERLY), reserpine-elderly withdrawal (RES-ELDERLY WITHDRAWAL), control-adult (CTL-ADULT), reserpine-adult (RES-ADULT), and reserpine-adult withdrawal (RES-ADULT WITHDRAWAL). Animals received 15 injections every other day of RES (0.1 mg / kg) or vehicle during 30 days. Throughout treatment, animals were evaluated in the catalepsy test (every 48 h) and open field test (24 h after the second injection), and weight assessment (every 4 days) was also made. Upon completion of behavioral tests, rat brains were collected for tyrosine hydroxylase (TH) immunohistochemical analysis. Main results demonstrated that RES-treated animals spent more time in the catalepsy bar compared with control groups, moreover the RES-elderly group showed a longer catalepsy time compared with the RES-ADULT group. A shorter time from RES treatment to the development of symptoms was observed in the RES-ADULT group, compared with the RES-ELDERLY group. In addition, RES-induced weight loss in both RES-ELDERLY and RES-ADULT when compared with their corresponding controls. Cessation of RES treatment was followed by weight gain only in the RES-ADULT group. A significant decrease in TH-immunoreactive cells was observed in the substantia nigra pars compacta (SNpc) and dorsal striatum (STR) in the rats in both the RES-ADULT and RES-ELDERLY groups and in the ventral tegmental area in rats in the RES-ADULT group. Furthermore, TH immunoreactivity decrease was not reversible in SNpc and STR in the RES-ELDERLY. These results show that RES has an age-dependent effect in rats, suggesting a greater sensitivity of the dopaminergic pathway to RES with advancing age. These suggest that the RES rat model of parkinsonism can be useful in improving our knowledge on the effect of aging on neurodegeneration.

Testosterone propionate improves motor alterations and dopaminergic damage in the reserpine-induced progressive model of Parkinson's disease

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder with a higher susceptibility to occur in men. Studies suggest that this susceptibility is related to the hormonal differences observed between men and women, being a risk factor for PD. In addition, testosterone supplementation has shown controversial results in animal models of PD and parkinsonian patients. This study evaluated the effect of chronic administration of testosterone propionate (TP) on motor behavior and neurochemical parameters in the reserpine-induced rat model of parkinsonism. Male Wistar rats received 15 injections of reserpine (RES - 0.1 mg/kg) every other day and were concomitantly treated with different doses (0.1, 1.0, or 5.0 mg/kg) of daily TP for 30 days. The rats were euthanized 48 h after the 15th injection of RES or vehicle. Brains were removed and subjected to Tyrosine hydroxylase (TH) immunohistochemistry. TP at 1.0 mg/kg reduced the damages caused by reserpine in the vacuous chewing and tong protrusion behaviors and prevented dopaminergic damage in the SNpc, VTA, and Striatum. TP at 5.0 mg/kg reduced the damages caused by reserpine in the catalepsy and tong protrusion behaviors, prevented the weight loss, and prevented dopaminergic damage in the VTA. Our results suggest that chronic administration of TP has a protective effect in a rat model of parkinsonism, improving motor alterations and dopamine depletion induced by RES.

Changes in the mesocorticolimbic pathway after low dose reserpine-treatment in Wistar and Spontaneously Hypertensive Rats (SHR): Implications for cognitive deficits in a progressive animal model for Parkinson's disease

Reserpine (RES) is an irreversible inhibitor of VMAT2 used to study Parkinson's disease (PD) and screening for antiparkinsonian treatments in rodents. Recently, the repeated treatment with a low dose of reserpine was proposed as a model capable of emulating progressive neurochemical, motor and non-motor impairments in PD. Conversely, compared to Wistar rats, Spontaneously Hypertensive Rats (SHR) are resistant to motor changes induced by repeated treatment with a low dose of RES. However, such resistance has not yet been investigated for RES-induced non-motor impairments. We aimed to assess whether SHR would have differential susceptibility to the object recognition deficit induced by repeated low-dose reserpine treatment. We submitted male Wistar and SHR rats to repeated RES treatment (15 s.c. injections of 0.1 mg/kg, every other day) and assessed object memory acquisition and retrieval 48 h after the 6^th RES injection (immediately before the appearance of motor impairments). Only RES Wistar rats displayed memory impairment after reserpine treatment. On the other hand, untreated SHR rats displayed object recognition memory deficit, but RES treatment restored such deficits. We also performed immunohistochemistry for tyrosine hydroxylase (TH) and α-synuclein (α-syn) 48 h after the last RES injection. In a different set of animals submitted to the same treatment, we quantified DA, 5-HT and products of lipid peroxidation in the prefrontal cortex (PFC) and hippocampus (HPC). SHR presented increased constitutive levels of DA in the PFC and reduced immunoreactivity to TH in the medial PFC and dorsal HPC. Corroborating the behavioral findings, RES treatment restored those constitutive alterations in SHR. These findings indicate that the neurochemical, molecular and genetic differences in the SHR strain are potentially relevant targets to the study of susceptibility to diseases related to dopaminergic alterations.

Balance alterations and reduction of pedunculopontine cholinergic neurons in early stages of parkinsonism in middle-aged rats

The purpose of the present study was to investigate balance alterations and the possible role of the cholinergic neurons in the pedunculopontine nucleus (PPN) in the early stages of a progressive animal model of Parkinson's disease (PD). Twenty-eight middle-aged (8-9 months) male Wistar rats received 4 or 10 subcutaneous vehicle (control, CTL) or reserpine (RES) injections (0.1 mg/kg). The animals were submitted to different behavioral tests. Forty-eight hours after the 4th injection, half of the animals of each group (n = 7) were perfused and submitted to immunohistochemical analysis for tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT). The remaining animals (n = 7 per group) were killed 48 h after the 10th injection. RES group presented motor deficits in the catalepsy and open field tests starting at days 12 and 20 of treatment, respectively (only for the animals that received 10 injections). On the other hand, dynamic and static balance changes were observed at earlier stages of RES treatment, starting at days 6 and 4, respectively. At this point of the treatment, there was no decrease in the number of TH immunoreactivity neurons in the substantia nigra pars compacta (SNpc), ventral tegmental area (VTA) and dorsal striatum (DS). However, a decrease was observed in SNpc and dorsal striatum of animals that received 10 injections. In contrast, there was a decrease in the number of ChAT immunoreactive cells in PPN concomitantly to the balance alterations at the early stages of treatment (after 4 RES injections). Thus, by mimicking the progressiveness of PD, the reserpine model made it possible to identify static and dynamic balance impairments prior to the motor alterations in the catalepsy and open field tests. In addition, changes in balance were accompanied by a reduction in the number of ChAT immunoreactive cells in NPP in the early stages of treatment.

Different response to instrumental tests in relation to cognitive demand after dopaminergic stimulation in previously treated patients with Parkinson's disease

Instrumental measurement of response assets and movement behaviour gained importance as addition to rating procedures to determine the efficacy of therapeutic interventions in patients with Parkinson's disease. Objectives were to determine the response to standardised 100 mg levodopa application with repeat performance of complex and simple instrumental tests in relation to scored motor behaviour in 53 previously treated patients. Levodopa improved rating scores of motor impairment, execution of complicated movement patterns and complex reaction time. Computed improvements in these instrumental test results correlated with each other. Execution of the simple reaction time paradigm and of plain movement sequences did not ameliorate after levodopa. The changes of these simple test results were not associated to each other. These different response patterns result from the higher cognitive demand of dopamine sensitive association areas of the prefrontal cortex and mesolimbic system for the complex test execution in contrast to the simple task performance.