Although results from the present study using two differentially selective and clinically-tested S1P agonists suggest that bradycardia in rats is mediated by S1P1 receptor activation, some pre-clinical studies have suggested that bradycardia may be elicited by S1P3 receptor stimulation and this has led to a high degree of controversy in the field and speculated differences between rodent and man. Here, MBTPS1 is linked to Bradycardia.