Animal experiment:

Rabbits[3]Male New Zealand White rabbits weighing 3.0-3.5 kg are used for this study. Effects of Vernakalant, Ranolazine and Tertiapin-Q on the atrial effective refractory period (AERP) in the control and rapid atrial pacing (RAP) rabbits. Vernakalant (left panels, 3 mg/kg, n=5 for each group), Ranolazine (middle panels; 10 mg/kg, n=6 for each group) or Tertiapin-Q (right panels; 0.03 mg/kg, n=5 for each group) is intravenously administered to the control or RAP rabbits. AERP is measured before and 10 min after the administration of each drug, which are shown in the lower panels.

Tertiapin-Q is a highly selective blocker of GIRK1/4 heterodimer and ROMK1 (Kir1.1).

Tertiapin-Q is a highly selective blocker of G protein-coupled inwardly rectifying potassium (GIRK1/4) heterodimer and renal outer medullary potassium channel (ROMK1, Kir1.1)[1]. Tertiapin-Q is a potent and selective blocker for Kir1.1 renal outer medullary potassium, Kir3.1-Kir3.4 channels and calcium activated large conductance potassium channels (big potassium channels). The somatostatin (SS-14)-activated current is almost completely blocked (93.2±2.9%, n=5; P<0.01) by preincubation with the G protein-coupled inwardly rectifying potassium (GIRK) channel blocker Tertiapin-Q (TPN-Q)[2].

Tertiapin-Q is a muscarinic acetylcholine receptor-operated K+ current (IK,Ach) blocker. After the cessation of rapid atrial pacing, the atrial effective refractory period (AERP) is unchanged during the experimental period in the rapid atrial pacing (RAP) rabbits (n=6). Bepridil (1 mg/kg, n=5 for each group), Amiodarone (10 mg/kg, n=5 for each group), Vernakalant (3 mg/kg, n=5 for each group), Ranolazine (10 mg/kg, n=6 for each group) or Tertiapin-Q (0.03 mg/kg, n=5 for each group) on the AERP in the control and RAP rabbits. Tertiapin-Q significantly prolongs the AERP at each pacing cycle length both in the control and RAP rabbits. The extents of prolonging effect of Tertiapin-Q on the AERP in the RAP rabbits are greater than those in the control animals[3].

References:
[1]. Picton LD, et al. Mechanisms underlying the endogenous dopaminergic inhibition of spinal locomotor circuit function in Xenopus tadpoles. Sci Rep. 2016 Oct 20;6:35749.
[2]. Günther T, et al. Research Resource: Real-Time Analysis of Somatostatin and Dopamine Receptor Signaling in Pituitary Cells Using a Fluorescence-Based Membrane Potential Assay. Mol Endocrinol. 2016 Apr;30(4):479-90.
[3]. Chiba T, et al. Influences of rapid pacing-induced electrical remodeling on pharmacological manipulation of the atrial refractoriness in rabbits. J Pharmacol Sci. 2016 Mar;130(3):170-6.