In vitro assessment for vascular selectivity of a new dihydropyridine derivative, NB-818

Imidazo[2,1-b]thiazole system: a scaffold endowing dihydropyridines with selective cardiodepressant activity

The synthesis, characterization, and functional in vitro assays in cardiac tissues and smooth muscle (vascular and nonvascular) of a number of 4-imidazo[2,1- b]thiazole-1,4-dihydropyridines are reported. The binding properties for the novel compounds have been investigated and the interaction with the binding site common to other aryl-dihydropyridines has been demonstrated. Interestingly, the novel 4-aryl-dihydropyridines are L-type calcium channel blockers with a peculiar pharmacological behavior. Indeed, the imidazo[2,1- b]thiazole system is found to confer to the dihydropyridine scaffold an inotropic and/or chronotropic cardiovascular activity with a high selectivity toward the nonvascular tissue. Finally, molecular modeling studies were undertaken for the most representative compounds with the aim of describing the binding properties of the new ligands at molecular level and to rationalize the found structure-activity relationship data. Due to the observed pharmacological behavior of our compounds, they might be promising agents for the treatment of specific cardiovascular pathologies such as cardiac hypertrophy and ischemia.

Mechanism of vasoselective action of mebudipine, a new calcium channel blocker

In previous studies, mebudipine, a newly synthesized dihydropyridine calcium channel blocker, showed a considerable vasoselective action. To investigate the mechanism of this property, the pattern of inhibitory action on the KCl-induced contraction in isolated rat aortic rings and the effect of changing resting membrane potential on the potency of this compound were considered. In addition, its chronotropic and inotropic actions were also studied. Mebudipine inhibited KCl-induced contractions. Its inhibitory effect was progressive and needed time to reach maximum. Incubation of the aortic rings in depolarizing physiological solution (high potassium, zero calcium) resulted in the augmentation of mebudipine effect. The potency of mebudipine in inhibiting aortic contractions and its time- and voltage-dependent action were significantly greater than those of nifedipine. In comparison with nifedipine, mebudipine showed a greater negative chronotropic effect, but in the case of negative inotropism, the reverse relation was observed. It is concluded that mebudipine has a greater time- and voltage-dependent inhibitory effect, as compared to nifedipine and this property could explain its prominent vasoselective action. It has also marked negative chronotropic effect and minor negative inotropic action. With regard to the above findings, mebudipine might have a selective and protective calcium channel blocking effect in ischemic regions (ischemia-selectivity), and the potential to be used in cardiovascular diseases without causing harmful effects such as reflex tachycardia and heart failure which have sometimes been seen with the older agents.