The effects of verapamil and diltiazem on N‐, P‐ and Q‐type calcium channels mediating dopamine release in rat striatum

Abstract

, and was insensitive to dihydropyridines (up to 30 mM). It was signi®cantly blocked by o-CTx-GVIA (1 mM), o-Aga-IVA (30 nM) and was con®rmed to be abolished by o-CTx-MVIIC (3 mM), indicating involvement of N-, P-and Q-type channel subtypes. , suggesting that Na + rather than Q-type Ca 2+ channels are involved. 5 Taken together, our results suggest that verapamil can block P-and at higher concentrations possibly N-and Q-type Ca 2+ channels linked to [ 3 H]-DA release, whereas diltiazem appears to block P-type Ca 2+ channels only.

Multiple Targets of μ-Opioid Receptor-Mediated Presynaptic Inhibition at Primary Afferent Aδ- and C-Fibers

“…When we used verapamil at 50 M in the present and in a previous study (Heinke et al, 2004), basal synaptic transmission was, however, mildly reduced. Since this phenylalkylamine at the concentration used may also block P/Q-type Ca 2ϩ channels (Cai et al, 1997;Dobrev et al, 1999) and various K ϩ channels (Gutman et al, 2005), we now conclude that L-type VDCCs do not significantly contribute to synaptic transmission at A␦-and C-fiber terminals. The different contributions of the VDCC subtypes to the DAMGO effect thus reflect the quantitative composition of N-and P/Q-Ca 2ϩ channel subtypes expressed on A␦-and C-fiber terminals (Heinke et al, 2004).…”

“…We found in the presence of this blocker a significant reduction by 29% of the DAMGO effect on A␦-fiber and by 14% on C-fiber terminals, respectively. The specificity of verapamil has, however, been challenged (Cai et al, 1997;Dobrev et al, 1999;Gutman et al, 2005). We therefore used additional, more specific inhibitors of L-type VDCCs.…”

L-Type Voltage-Gated Calcium Channels in the Basolateral Amygdala Are Necessary for Fear Extinction

“…However, it is well known that verapamil can interfere with other VGCCs such as the P-and Q-subtypes (Ishibashi et al, 1995;Dobrev et al, 1999) as well as with potassium channels (Waldegger et al, 1999) and ␣-adrenergic receptors (Müller and Noack, 1988). We therefore repeated the above experiments using the more specific L-VGCC antagonist and dihydropyridine drug nifedipine.…”

Vascular Smooth Muscle Cells Express the α 1A Subunit of a P-/Q-Type Voltage-Dependent Ca 2+ Channel, and It Is Functionally Important in Renal Afferent Arterioles

“…In this context, it is interesting to note that L-type Ca 2ϩ channel blockers, such as the dihydropyridines, verapamil, and diltiazem, have been reported to significantly inhibit P-type Ca 2ϩ currents when used in concentrations that are not maximal for the L-type blockade. 34,35 It is therefore likely that the role of L-type Ca 2ϩ channels has been overestimated and that the response to therapeutic concentrations of these compounds includes the sum of inhibiting at least Land P-type Ca 2ϩ channels. We conclude that mRNA and protein encoding an ␣ 1A subunit for a P-/Q-type Ca 2ϩ current is expressed in VSMCs and mesangial cells, and we provide evidence that P-type VDCCs play a significant functional role in A7r5 cells and in renal afferent arterioles.…”