VIPR1 and relapsing-remitting multiple sclerosis: VIPR1 expression was significantly increased in the NAWM of RRMS cases (t9 = 2.527; * p < 0.05; Figure 3B′), as well as in PPMS cases, although not at a statistically significant level (t8 = 2.058; p = 0.074; Figure 3B′′′).