HTR1A and Bradycardia: Transgenic mice overexpressing 5-HT1A receptors show prolonged episodes of bradycardia, and 5-HT1A agonists induce bradycardia (Ramage, 1990; Jordan, 2005; Audero et al., 2008; Ramage and Villalon, 2008; Restrepo et al., 2010).