1-Methyl-4-Phenylpyridinium Stereotactic Infusion Completely and Specifically Ablated the Nigrostriatal Dopaminergic Pathway in Rhesus Macaque

Abstract

IntroductionComplete and specific ablation of a single dopaminergic (DA) pathway is a critical step to distinguish the roles of DA pathways in vivo. However, this kind of technique has not been reported in non-human primates. This study aimed to establish a lesioning method with a complete and specific ablation.MethodA carefully designed infusion route based on a MRI stereotactic technique was developed to deliver the highly selective dopaminergic toxin 1-methyl-4-phenylpyridinium (MPP+) unilaterally into multiple sites of compact part of substantia nigra (SNc) and striatum in monkeys. The nigrostriatal DA pathway was selected because lesioning of this pathway may induce symptoms that are suitable for evaluation. The pathological, behavioral, neuropharmacological, and clinical laboratorial data were collected to evaluate the lesioning effects.ResultPathological examination revealed a complete ablation of tyrosine hydroxylase positive (TH+) neurons in the SNc, while preserving intact TH+ neurons in the ventral tegmental area (VTA) nearby. TH+ projections in the striatum were also unilaterally lost. The monkeys displayed stable (>28 weeks) rotations and symptoms which were expected with loss of DA neurons in the SNc, with rest tremor being an exception. No item implied the presence of a severe side effect caused by the operation or the intracerebral MPP+ infusion. The results suggested that rest tremor may not directly rely on the nigrostriatal pathway.ConclusionTaken together, in addition to providing a specific nigrostriatal DA lesioned model, this method, combined with brain stimulation or other techniques, can be applied as a powerful tool for the complete lesion of any desired DA pathway in order to study its specific functions in the brain.

Co-editingPINK1andDJ-1genes via AAV-delivered CRISPR/Cas9 system in adult monkey brains elicits classic Parkinsonian phenotypes

“…In hemi-Parkinsonism monkey model, the behavioral phenotypes are sensitively to be measured, including the apomorphine-induced rotation and hand preference test. Here, to ensure a whole coverage of viral injections in the targeted SN, we performed the AAV injections into the targeted side of the SNs of each monkey brain through three oblique parallel pathways, which had been determined by a unique magnetic resonance imaging (MRI)-guided high accuracy localization procedure (error < 1 mm) previously developed in our lab (26,27) Table S2). Six weeks after the viral injections, the total PD score of each monkey was marked by the improved version of Kurlan scale (a Monkey-Parkinsonism Rating Scale) (28), which has been widely used in PD monkey studies (29).…”

“…Here, the unique oblique injection routes (Fig. 1F) were employed based on our previous study (27). To cover the whole SN, we injected virus along three parallel paths through the SN, with an average of six injection sites in each path.…”

“…1E, white arrows), being fixed onto the skull of each monkey before MRI scanning. Details of the marker fixation and MRI scanning procedures for deep brain region localization have been published previously by our lab (error < 1mm) (26), and this method was successfully used to accurately locate the SN of the rhesus monkey brain in our previous PD study (27). The markers appeared as two light and parallel lines in the middle coronal section during MRI scanning; as a result, this coronal plane was accurately determined by the two markers with a definitive locations: 10 mm before the A (anterior) / P The SN was clearly seen on the T2 images with low signal intensity, appearing black (Fig.…”

“…The next step of video analyzing process was based on previous studies (27,44). Here, two well trained observers were involved in the video clips analyzing.…”

“…The main brain structure involved in PD pathology is the SN, a paired flat shaped structure located deep in the narrow mesencephalon (27). The SN was located from -9.90 mm to -17.78 mm AP from bregma according to the monkey brain atlases "The Rhesus Monkey Brain in Stereotaxic Coordinates, George Praxinos et al, Academic Press, 1999", and it was further confirmed by the MRI data, proving the length of the SN is about 8.00 mm from anterior to the posterior.…”