Evaluating Plasma and Brain TRPV1 Channels in the Animal Model of Episodic and Chronic Migraine: The Possible Role of Somatosensory Cortex TRPV1 in Migraine Transformation

Background: Despite extensive research, the exact molecular mechanisms underlying migraine development and especially its progression and transformation from episodic into chronic is still unknown. Objectives: This study aimed to assess the role of somatosensory cortex and hippocampal transient receptor potential vanilloid 1 (TRPV1) in migraine in a rat model. Methods: Adult male Wistar rats were divided into three groups, including sham, episodic migraine (EM), and chronic migraine (CM). The sham group received normal intraperitoneal (IP) saline injections every two days for 11 days, and the EM group received a single dose of trinitroglycerin (TNG) injection (IP; 10 mg/kg). For the CM group, TNG was administrated every two days (on days 3, 5, 7, 9, and 11; IP; 10 mg/kg). TRPV1 levels in plasma, somatosensory cortex, and hippocampus were detected with an enzyme-linked immunosorbent assay (ELISA) kit. Results: The findings showed that in both CM and EM groups the TRPV1 levels in plasma (P < 0.001 in both groups), somatosensory cortex (P < 0.05 and P < 0.001, respectively), and hippocampus (P < 0.01 in both groups) increased after migraine induction. Interestingly, in the somatosensory cortex, this TRPV1 elevation in the CM group was much greater than the EM group, and a significant difference was observed between the two groups (P < 0.05). Conclusions: Our results suggested that headache severity and frequency may enhance concomitant with the upregulation of somatosensory cortex TRPV1. This new achievement can help to develop new drug approaches to prevent CM.