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

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Dobrev D, Milde AS, Andreas K, Ravens U

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

Br J Pharmacol. 1999 May;127(2):576-82. doi: 10.1038/sj.bjp.0702574.

PubMed ID

10385261 [ View in PubMed

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Abstract

1. The putative inhibitory effects of verapamil and diltiazem on neuronal non-L-type Ca2+ channels were studied by investigating their effects on either K+- or veratridine-evoked [3H]-dopamine ([3H]-DA) release in rat striatal slices. Involvement of N-, P- and Q-type channels was identified by sensitivity of [3H]-DA release to omega-conotoxin GVIA (omega-CTx-GVIA), omega-agatoxin IVA (omega-Aga-IVA) and omega-conotoxin MVIIC (omega-CTx-MVIIC), respectively. 2. KCl (50 mM)-evoked [3H]-DA release was abolished in the absence of Ca2+, and was insensitive to dihydropyridines (up to 30 microM). It was significantly blocked by omega-CTx-GVIA (1 microM), omega-Aga-IVA (30 nM) and was confirmed to be abolished by omega-CTx-MVIIC (3 microM), indicating involvement of N-, P- and Q-type channel subtypes. 3. Verapamil and diltiazem inhibited K+-evoked [3H]-DA release in a concentration-dependent manner. The inhibitory effects of verapamil or diltiazem (each 30 microM) were fully additive to the effect of omega-CTx-GVIA (1 microM), whereas co-application with omega-Aga-IVA (30 nM) produced similar effects to those of omega-Aga-IVA alone. 4. As shown previously, veratridine-evoked [3H]-DA release in Ca2+ containing medium exclusively involves Q-type Ca2+ channels. Here, diltiazem (30 microM) did not inhibit veratridine-evoked [3H]-DA release, whereas verapamil (30 microM) partially inhibited it, indicating possible involvement of Q-type channels in verapamil-induced inhibition. However, verapamil (30 microM) inhibited this release even in the absence of extracellular Ca2+, suggesting that Na+ rather than Q-type Ca2+ channels are involved. 5. Taken together, our results suggest that verapamil can block P- and at higher concentrations possibly N- and Q-type Ca2+ channels linked to [3H]-DA release, whereas diltiazem appears to block P-type Ca2+ channels only.

DrugBank Data that Cites this Article

Drugs

Verapamil

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Verapamil	Voltage-dependent N-type calcium channel subunit alpha-1B	Protein	Humans	Unknown	Inhibitor	Details
Verapamil	Voltage-dependent P/Q-type calcium channel subunit alpha-1A	Protein	Humans	Unknown	Inhibitor	Details