Contrasting the effects of nifedipine on subtypes of endogenous and recombinant T-type Ca2+ channels

Multiple T-type Ca2+ current subtypes in electrophysiologically characterized hamster dorsal horn neurons: possible role in spinal sensory integration

“…We used an indirect method in the present study to distinguish subtypes of T-currents in dorsal horn neurons based on differences in kinetics of inactivation. The results suggest that the net T-current is composed of "fast" and "slow" components, having decay time constants similar to two subtypes of low-voltage-activated Ca 2ϩ currents reported for thalamic neurons (Shcheglovitov et al 2005;Zhuravleva et al 1999Zhuravleva et al , 2001. The current densities for the dorsal horn subtypes (ϳ3-4 pA/pF) are similar to neurons recorded in thalamic slices (Tarasenko et al 1997), and the two subtypes appear to be present in approximately equal ratios in the spinal cord and thalamus.…”

“…Previous studies in thalamic neurons (Shcheglovitov et al 2005; Tarasenko et Zhuravleva et al 1999Zhuravleva et al , 2001 suggested that multiple channel subtypes may contribute to the net T-current in dorsal horn neurons when the high-voltage-activated Ca 2ϩ current is blocked. We found that for the majority of cells (67%, 29/43), I T could be dissected into two components based on time constants of decay (Fig.…”

The Role of L- and T-Type Calcium Channels in Local and Remote Calcium Responses in Rat Mesenteric Terminal Arterioles

“…8). Nimodipine has long been recognized as a partial blocker of T-type channels [32, 39], and it has been reported that nifedipine blocks both native and recombinant T-type currents, with the highest sensitivity (IC 50 = 1.2–5 µ M ) displayed by currents carried via Ca V 3.2 channels [40, 41]. Thus, the moderate efficacy obtained with nifedipine in mesenteric terminal arterioles may suggest that its effects are due to a predominant expression of T-type channels in this preparation.…”

Mechanism underlying the block of human Cav3.2 T-type Ca2+ channels by benidipine, a dihydropyridine Ca2+ channel blocker

“…The blocking activity of benidipine against hCav3.2 T-type Ca 2+ channels in this study was similar to that against endogenous T-type Ca 2+ channels (Akizuki et al, 2008), but was more potent than that against Ca v 3.1, Ca v 3.2, and Ca v 3.3 T-type Ca 2+ channels expressed in Xenopus oocytes (Furukawa et al, 2005(Furukawa et al, , 2009). The differences in the blocking activity of benidipine are likely due to the different experimental conditions, because the blocking activity of T-type Ca 2+ channel blockers has been demonstrated to be dependent on the permeant ion concentration, charge carrier, and host cell type (Martin et al, 2000;Furukawa et al, 2004;Shcheglovitov et al, 2005;Freeze et al, 2006).…”