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Ritanserin blocks CaV1.2 channels in rat artery smooth muscles: electrophysiological, functional, and computational studies

	author = {Fabio Fusi and Alfonso Trezza and Giampietro Sgaragli and Ottavia Spiga and Simona Saponara and Sergio Bova},
	title = {Ritanserin blocks CaV1.2 channels in rat artery smooth muscles: electrophysiological, functional, and computational studies},
	journal = {Acta Pharmacologica Sinica},
	volume = {41},
	number = {9},
	year = {2020},
	keywords = {},
	abstract = {CaV1.2 channel blockers or 5-HT2 receptor antagonists constitute effective therapy for Raynaud’s syndrome. A functional link between the inhibition of 5-HT2 receptors and CaV1.2 channel blockade in arterial smooth muscles has been hypothesized. Therefore, the effects of ritanserin, a nonselective 5-HT2 receptor antagonist, on vascular CaV1.2 channels were investigated through electrophysiological, functional, and computational studies. Ritanserin blocked CaV1.2 channel currents (ICa1.2) in a concentration- dependent manner (Kr = 3.61 μM); ICa1.2 inhibition was antagonized by Bay K 8644 and partially reverted upon washout. Conversely, the ritanserin analog ketanserin (100 μM) inhibited ICa1.2 by ~50%. Ritanserin concentration-dependently shifted the voltage dependence of the steady-state inactivation curve to more negative potentials (Ki = 1.58 μM) without affecting the slope of inactivation and the activation curve, and decreased ICa1.2 progressively during repetitive (1 Hz) step depolarizations (use- dependent block). The addition of ritanserin caused the contraction of single myocytes not yet dialyzed with the conventional method. Furthermore, in depolarized rings, ritanserin, and to a lesser extent, ketanserin, caused a concentration-dependent relaxation, which was antagonized by Bay K 8644. Ritanserin and ketanserin were docked at a region of the CaV1.2 α1C subunit nearby that of Bay K 8644; however, only ritanserin and Bay K 8644 formed a hydrogen bond with key residue Tyr-1489. In conclusion, ritanserin caused in vitro vasodilation, accomplished through the blockade of CaV1.2 channels, which was achieved preferentially in the inactivated and/or resting state of the channel. This novel activity encourages the development of ritanserin derivatives for their potential use in the treatment of Raynaud’s syndrome.},
	issn = {1745-7254},	url = {}