J Neurosci Methods. 2026 May 6;433:110790. doi: 10.1016/j.jneumeth.2026.110790. Online ahead of print. ABSTRACT BACKGROUND: Toe-clipping and ear-tagging are standard rodent identification methods. Their potential to confound outcomes in Parkinson's disease (PD) research remains…
J Neurosci Methods. 2026 May 6;433:110790. doi: 10.1016/j.jneumeth.2026.110790. Online ahead of print.
ABSTRACT
BACKGROUND: Toe-clipping and ear-tagging are standard rodent identification methods. Their potential to confound outcomes in Parkinson's disease (PD) research remains poorly characterized.
NEW METHOD: We evaluated the methodological impacts of these procedures in a C57BL/6 male mouse PD model using behavioral assays and neuropathological analyses.
RESULTS: Toe-clipping triggered sustained neuroinflammation, with 5-toe clipped mice showing elevated Interleukin (IL)-1β compared to ear-tagged (mean difference = 0.3647, 95% CI: 0.1203-0.6090, P = 0.0025) and 2-toe clipped mice (mean difference = 0.2333, 95% CI: 0.00036-0.4663, P = 0.0496) in non-PD conditions. In PD conditions, 5-toe clipped mice exhibited elevated IL-1β compared to non-PD 5-toe clipped mice (mean difference = 0.3967, 95% CI: 0.1123-0.6810, P = 0.0016). Toe-clipping exacerbated motor deficits, with significant grip strength impairments in 5-toe versus control mice (mean difference = 1.513, 95% CI: 0.01114-3.016, P = 0.0479) and in PD-5-toe versus PD-control mice (mean difference = 2.542, 95% CI: 1.132-3.951, P = 0.0003). In contrast, ear-tagging selectively impaired pole test performance, with ear-tagged mice showing prolonged head-turning times versus controls (mean difference = 1.232, 95% CI: 0.3723-2.091, P = 0.0035) and 2-toe mice (mean difference = 1.438, 95% CI: 0.5789-2.298, P = 0.0008), effects maintained after PD modeling (PD-ear-tagged vs PD-control: mean difference = 1.367, 95% CI: 0.6123-2.121, P = 0.0003). Swimming speed did not differ between groups (P = 0.9891).
COMPARISON WITH EXISTING METHODS: This study demonstrates that routine identification methods significantly influence PD research outcomes. The induced confounds-chronic neuroinflammation from toe-clipping and sensorimotor disruption from ear-tagging-can mimic or mask PD pathology, threatening data validity.
CONCLUSION: Identification methods must be documented as critical methodological variables. Adoption of non-invasive alternatives is imperative for rigor and reproducibility in neurodegenerative research.
PMID:42102894 | DOI:10.1016/j.jneumeth.2026.110790