Substance P as a potential biomarker of pain assessment in dogs

Background: Substance P (SP) is a neuropeptide that functions as a neuromodulator. It is released mainly in the brain stem and in nerve endings. Aims: The present study aimed to provide fundamental data that may be applied to the assessment of pain in dogs by evaluating their serum SP concentrations. Methods: Two groups of dogs were designated as pain groups that included 10 dogs with medial patella luxation (MPL) and 10 dogs with fractures, respectively, and 20 healthy dogs were enrolled as the control group. Results: The SP concentrations in the serum of the pain groups reached 485.5 ± 250.1 pg/ml that was significantly higher than those of the control group, which reached 116.4 ± 38.5 pg/ml. In particular, serum SP concentrations in dogs with fractures (663.3 ± 225.3 pg/ml) were significantly higher compared to those of dogs with MPL (307.8 ± 105.3 pg/ml), indicating that serum SP levels increased when the dogs experienced greater pain. Conclusion: These findings propose the possibility that SP might be a useful biomarker for pain assessment in dogs. The present study may provide fundamental data that can aid in future pain management in dogs.