In Parkinson’s disease (PD), progressive degeneration of nigrostriatal innervation leads to atrophy and loss of dendritic spines of striatal medium spiny neurons (MSNs). The loss disrupts corticostriatal transmission, impairs motor behavior, and produces nonmotor symptoms. Nigral neurons express brain-derived neurotropic factor (BDNF) and dopamine D3 receptors, both protecting the dopamine neurons and the spines of MSNs. To restore motor and nonmotor symptoms to normality, we assessed a combined therapy in a bilateral rat Parkinson’s model, with only 30% of surviving neurons. The preferential D3 agonist pramipexole (PPX) was infused for four ½ months via mini-osmotic pumps and one month after PPX initiation; the BDNF-gene was transfected into the surviving nigral cells using the nonviral transfection NTS-polyplex vector. Overexpression of the BDNF-gene associated with continuous PPX infusion restored motor coordination, balance, normal gait, and working memory. Recovery was also related to the restoration of the average number of dendritic spines of the striatal projection neurons and the number of TH-positive neurons of the substantia nigra and ventral tegmental area. These positive results could pave the way for further clinical research into this promising therapy.

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder, yet its pathogenic mechanisms remain incompletely understood, highlighting the need for reliable experimental models. We previously developed a murine model based on inhalation of a manganese mixture (MnCl₂ and Mn(OAc)₃), which reproduces dopaminergic neuron loss in the substantia nigra pars compacta (SNc) and motor impairment. However, its capacity to mimic mitochondrial dysfunction, a key mechanism in PD, had not been explored. This study evaluated mitochondrial ultrastructure, fission and fusion proteins, and the activity of electron transport chain complexes I and IV, alongside fine motor performance. Forty male CD1 mice were divided into control (deionized water) and manganese-exposed groups (0.04 M MnCl₂ + 0.02 M Mn(OAc)₃), inhaled for 1 h twice weekly over five months. Manganese inhalation induced significant fine motor deficits, increased mitochondrial number with reduced area and circularity, and disorganized cristae. Drp1 and Fis1 levels were elevated, accompanied by decreased activity of complexes I and IV, predominantly in the SNc. These findings demonstrate that this progressive, bilateral model reproduces mitochondrial and motor alterations resembling those observed in PD, supporting its utility for testing mitochondria-targeted therapeutic strategies.

Parkinson’s disease (PD) experimental models are crucial in the assessment of possible therapies. Nevertheless, even though PD was one of the first neurodegenerative conditions to be modeled, there are limitations such as spontaneous recovery; lack of bilateral damage, which is a PD characteristic; animal intensive care after neurotoxin administration; and ultrastructural and biochemical nonspecific alterations but mostly the neurodegenerative time course observed in humans. In this chapter, we investigated the effects of divalent and trivalent manganese inhalation on rats and mice to obtain a novel PD animal model inducing bilateral and progressive dopaminergic cell death. We found that after 5 or 6 months of inhalation, there was more than 70% decrease in the number of TH-immunopositive neurons, and these alterations are correlated with an evident motor performance deficits manifested as akinesia, postural instability, and action tremor. More interesting is the fact that these alterations were reverted with l-DOPA treatment, implying that the motor alterations are associated with nigrostriatal dopaminergic innervation, postulating new light for the understanding of manganese neurotoxicity as an appropriate PD experimental model. Our results are contributing to the development of a suitable PD animal model, reproducible, sensitive, time-efficient, and readily applicable behavioral tests.

Chronic exposure to vanadium pentoxide (V₂O₅) has been linked to neuronal damage equivalent to that found in Alzheimer’s disease (AD). Prior research has indicated that chronic inhalation of V₂O₅ results in cellular and behavioral changes akin to those observed in AD. A total of 40 male Wistar rats were categorized into two control groups and two experimental groups for the study. The experimental inhaled V₂O₅ for 6 months; after 6 months, two groups (control and exposed) were left in a 6-month recovery phase. All groups were evaluated monthly for 6 or 12 months in a spatial memory test. To measure histological alterations, hippocampus CA1, entorhinal and frontal cortices, amygdala, and subiculum underwent Congo red or argentic Bielschowsky impregnation and were analyzed. Memory results show impairment since the third month. The group left in recovery did not show improvement. Chronic V₂O₅ inhalation is an AD model that causes irreversible alterations in spatial memory, accumulation of Aβ plaques, accumulation of NFTs, and loss of dendritic spines with no recovery. These alterations are not reversible after 6 months, indicating that the damage increases once the neurodegenerative process is established and the homeostasis is broken. This model characterizes sporadic AD, representing more than 95% of cases.

Parkinson?s disease (PD) higher incidence has been observed in postmenopausal women compared to premenopausal women, suggesting estrogen neuroprotective effect. L-DOPA (LD) chronic treatment causes dyskinesia; evidences indicate that LD increases the preexisting oxidative stress condition. This study determines melatonin ability, alone or in combination with LD (LD/Mel) to protect dopaminergic loss induced by 6-OHDA in a rat PD model in ovariectomized (OVX) and intact (with ovaries (W/OV)) rats on motor behavior and cytological alterations, comparing with LD-only treated rats. LD/Mel-treated rats showed dyskinesia decrease (score 5–7.5) and had the best performance in the staircase test (five pellets) throughout all studies. The beam walking time was 20–35 s, showing good coordination (as control group (20–38 s)), dopaminergic cells increase of 22.8% (W/OV rats) and 27.2% (OVX rats) in the contralateral side as well as 100% conservation in the contralateral dendritic spines. Our results suggest that LD/Mel co-administration and estrogen presence result in an efficient treatment to reduce dyskinesia through the conservation of some dopaminergic cells, which imply a well-preserved neuropil of a less denervated striatum. We assume that these results are because of a synergistic effect between LD, melatonin and estrogens.