Application of the Physical Disector Principle for Quantification of Dopaminergic Neuronal Loss in a Rat 6-Hydroxydopamine Nigral Lesion Model of Parkinson's Disease

Abstract

Stereological analysis is the optimal tool for quantitative assessment of brain morphological and cellular changes induced by neurotoxic lesions or treatment interventions. Stereological methods based on random sampling techniques yield unbiased estimates of particle counts within a defined volume, thereby providing a true quantitative estimate of the target cell population. Neurodegenerative diseases involve loss of specific neuron types, such as the midbrain tyrosine hydroxylase-positive dopamine neurons in Parkinson's disease and in animal models of nigrostriatal degeneration. Therefore, we applied an established automated physical disector principle in a fractionator design for efficient stereological quantitative analysis of tyrosine hydroxylase (TH)-positive dopamine neurons in the substantia nigra pars compacta of hemiparkinsonian rats with unilateral 6-hydroxydopamine (6-OHDA) lesions. We obtained reliable estimates of dopamine neuron numbers, and established the relationship between behavioral asymmetry and dopamine neuron loss on the lesioned side. In conclusion, the automated physical disector principle provided a useful and efficient tool for unbiased estimation of TH-positive neurons in rat midbrain, and should prove valuable for investigating neuroprotective strategies in 6-OHDA model of parkinsonism, while generalizing to other immunohistochemically-defined cell populations.

Quantitative whole-brain 3D imaging of tyrosine hydroxylase-labeled neuron architecture in the mouse MPTP model of Parkinson's disease

“…Dopamine neurons have been intensely studied in humans and animal models of neurodegenerative diseases, as deficient function of dopaminergic neuron clusters in the SNc–VTA complex is closely related to the pathogenesis of PD and plays an important role in a range of other CNS diseases such as Huntington's disease and schizophrenia, as well as food and drug addiction (Grace and Gomes, 2019; Kenny, 2011; Klein et al, 2019; Obeso et al, 2008; Volkow et al, 2017). Unbiased estimates of TH+ dopaminergic neuron numbers is fundamental in the assessment of histopathological changes and neuroprotective drug treatment effects in preclinical models of PD (Fabricius et al, 2017). Previous LSFM studies have only provided a qualitative view on the distribution of TH-expressing neurons in individual mouse brains (Godefroy et al, 2017, 2019; Renier et al, 2014).…”

“…Stereological methods based on the optical fractionator method and unbiased counting rules have been considered the gold standard for estimation of the total number of TH+ neurons in a given brain structure (Eriksen et al, 2009; Gundersen et al, 1988; Schmitz and Hof, 2005; West et al, 1991). Although stereological approaches have provided the most consistent results on cell counts, the method is labor-intensive and time-consuming and therefore most often applied for quantitative assessment of TH+ neurons in discrete areas of the midbrain (Baquet et al, 2005; Chermenina et al, 2015; Fabricius et al, 2017; Garcia-Reitboeck et al, 2013; Hansen et al, 2016; Joyce et al, 2004; Komnig et al, 2016; Pakkenberg et al, 1995; Smeyne et al, 2016). Similar limitations apply to determination of dopaminergic projections estimated by manually counting visible TH+ fibers (Straub et al, 2008), which are therefore usually evaluated semi-quantitatively by 2D optical density analysis on thin sections (Joyce et al, 2004; Komnig et al, 2016).…”

Qinglong Zhidong Decoction Alleviated Tourette Syndrome in Mice via Modulating the Level of Neurotransmitters and the Composition of Gut Microbiota

“…D1R is a highly sensitive and expressive indicator of direct pathway striatal neurons. It promotes the DA and D1R binding, which can induce the stereotyped behavior (e.g., sniffing, biting, gnawing, and licking) in mice ( Fabricius et al, 2017 ). D2R is widely discovered in medium spiny neurons (MSN) and DA neurons in the basal ganglia and is an essential target for the treatment of the disorders exhibiting aberrant DA functions such as TS and schizophrenia.…”

Acupuncture protects from 6-OHDA-induced neuronal damage by balancing the ratio of DMT1/Fpn1

“…TH is a key enzyme in dopamine synthesis and a marker for dopaminergic neurons (Shahnawaz Khan et al, 2012). In the MFB model, the number of TH + DA neurons in SN is close to complete loss (10% compared to untreated) in 6-OHDA-induced rats with complete unilateral injury (Fabricius et al, 2017). Within 3 weeks after unilateral MFB injury, the striatum completely loses its dopamine content, while the number of dopaminergic neurons is gradually decreased.…”