TRPA1 and diabetes mellitus: However, the acute effect of guanfacine in reducing pain transmission in T1DM but not in control rats may be related to its ability to inhibit diabetes-induced upregulation in the expression of key neuronal hyperalgesic molecules such as transient receptor potential vanilloid 1 (TRPV1) and/or transient receptor potential ankyrin 1 (TRPA1) in several regions associated with pain transmission.