We present a robust, fresh-frozen approach to immunohistochemistry (IHC), without committing the tissue to IHC via fixation and cryopreservation while maintaining long-term storage, using LiCor-based infrared (IR) quantification for sensitive assessment of TH in immunoreacted mid-brain sections for quantitative comparison across studies. In fresh-frozen tissue stored up to 1 year prior to IHC reaction, we found our method to be highly sensitive to rotenone treatment in 3-month-old Sprague-Dawley rats, and correlated with a significant decline in rotarod laten-cy-to-fall measurement by approximately 2.5 fold. The measured midbrain region revealed a 31% lower TH signal when compared to control (p<0.01 by t test, n=5). Bivariate analysis of in-tegrated TH counts versus rotarod latency-to-fall indicates a positive slope and modest but sig-nificant correlation of R2=0.68 (p<0.05, n=10). These results indicate this rapid, instrument-based quantification method by IR detection successfully quantifies TH levels in rat brain tissue, while taking only 5 days from euthanasia to data output. This approach also allows for the identifica-tion of multiple targets by IHC with the simultaneous performance of downstream molecular analysis within the same animal tissue, allowing for the use of fewer animals per study.