S1PR1 and Bradycardia: In support of this hypothesis, Murakami et al. [41] demonstrated that although the S1P3 antagonist, TY-52156, could partially inhibit FTY720-induced bradycardia in vivo, the effect of FTY720 in the presence of TY-52156 was still markedly attenuated vs. vehicle controls (40–50 beats/min) suggesting another S1P receptor subtype, likely S1P1, was responsible for the majority of the bradycardia observed in the study.