Inhibition of type a GABA receptors by L-type calcium channel blockers

P. Das, C. L. Bell-Horner, Ren-Qi Huang, A. Raut, E. B. Gonzales, Z. L. Chen, D. F. Covey, G. H. Dillon

Research output: Contribution to journalArticleResearchpeer-review

30 Citations (Scopus)

Abstract

Modulation of type A GABA receptors (GABAA) by L-type Ca ++ channel blockers was investigated. The dihydropyridines nifedipine and nitrendipine, and the phenylalkylamine verapamil inhibited recombinant rat α1β2γ2 receptors recorded from human embryonic kidney (HEK) 293 cells; nifedipine at low concentrations also elicited modest stimulatory effects on GABA-gated current. The IC50 for GABA current inhibition was lowest for nitrendipine (17.3±1.3 μM), so subsequent studies were focused on further exploring its mechanism and possible site of action. When co-applied with GABA, nitrendipine had minimal effects on initial current amplitude, but significantly enhanced current decay rate. Nitrendipine-mediated inhibition was subunit-selective, as its IC50 was 10-fold lower in α1β2 receptors. Nitrendipine's effect in recombinant human α1β2γ2 receptors was similar (IC 50=23.0±1.3 μM) to that observed in rat receptors of the same configuration, indicating the site of action is conserved in the two species. The inhibitory effects were dependent on channel gating, were independent of transmembrane voltage, and were also observed in GABA A receptors recorded from hypothalamic brain slices. The pharmacologic mechanism of inhibition by nitrendipine was non-competitive, indicating it does not act at the GABA binding site. Nitrendipine block was retained in the presence of the benzodiazepine antagonist flumazenil, indicating it does not interact at the benzodiazepine site. The actions of nitrendipine were not affected by a mutation (β2T246F) that confers resistance to the channel blocker picrotoxin, and they were not altered in the presence of the picrotoxin site antagonist α-isopropyl-α-methyl- γ-butyrolactone, demonstrating nitrendipine does not act at the picrotoxin site of the GABAA receptor. Possible interaction of nitrendipine with the Zn++ site was also eliminated, as mutation of β2 H267 to A, which confers resistance to Zn++, had no effect on nitrendipine-mediated inhibition. Our data suggest some of the central effects of dihydropyridines may be due to actions at GABAA receptors. Moreover, the effects may be mediated through interaction with a novel modulatory site on the GABAA receptor.

Original languageEnglish
Pages (from-to)195-206
Number of pages12
JournalNeuroscience
Volume124
Issue number1
DOIs
StatePublished - 1 Jan 2004

Fingerprint

Nitrendipine
L-Type Calcium Channels
GABA Receptors
Calcium Channel Blockers
GABA-A Receptors
Picrotoxin
gamma-Aminobutyric Acid
Dihydropyridines
Nifedipine
Benzodiazepines
Inhibitory Concentration 50
Flumazenil
Mutation
Verapamil
Binding Sites

Keywords

  • Cl channel
  • Dihydropyridine
  • L-type Ca channel
  • Recombinant receptor

Cite this

Das, P., Bell-Horner, C. L., Huang, R-Q., Raut, A., Gonzales, E. B., Chen, Z. L., ... Dillon, G. H. (2004). Inhibition of type a GABA receptors by L-type calcium channel blockers. Neuroscience, 124(1), 195-206. https://doi.org/10.1016/j.neuroscience.2003.12.005
Das, P. ; Bell-Horner, C. L. ; Huang, Ren-Qi ; Raut, A. ; Gonzales, E. B. ; Chen, Z. L. ; Covey, D. F. ; Dillon, G. H. / Inhibition of type a GABA receptors by L-type calcium channel blockers. In: Neuroscience. 2004 ; Vol. 124, No. 1. pp. 195-206.
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Das, P, Bell-Horner, CL, Huang, R-Q, Raut, A, Gonzales, EB, Chen, ZL, Covey, DF & Dillon, GH 2004, 'Inhibition of type a GABA receptors by L-type calcium channel blockers', Neuroscience, vol. 124, no. 1, pp. 195-206. https://doi.org/10.1016/j.neuroscience.2003.12.005

Inhibition of type a GABA receptors by L-type calcium channel blockers. / Das, P.; Bell-Horner, C. L.; Huang, Ren-Qi; Raut, A.; Gonzales, E. B.; Chen, Z. L.; Covey, D. F.; Dillon, G. H.

In: Neuroscience, Vol. 124, No. 1, 01.01.2004, p. 195-206.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Inhibition of type a GABA receptors by L-type calcium channel blockers

AU - Das, P.

AU - Bell-Horner, C. L.

AU - Huang, Ren-Qi

AU - Raut, A.

AU - Gonzales, E. B.

AU - Chen, Z. L.

AU - Covey, D. F.

AU - Dillon, G. H.

PY - 2004/1/1

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N2 - Modulation of type A GABA receptors (GABAA) by L-type Ca ++ channel blockers was investigated. The dihydropyridines nifedipine and nitrendipine, and the phenylalkylamine verapamil inhibited recombinant rat α1β2γ2 receptors recorded from human embryonic kidney (HEK) 293 cells; nifedipine at low concentrations also elicited modest stimulatory effects on GABA-gated current. The IC50 for GABA current inhibition was lowest for nitrendipine (17.3±1.3 μM), so subsequent studies were focused on further exploring its mechanism and possible site of action. When co-applied with GABA, nitrendipine had minimal effects on initial current amplitude, but significantly enhanced current decay rate. Nitrendipine-mediated inhibition was subunit-selective, as its IC50 was 10-fold lower in α1β2 receptors. Nitrendipine's effect in recombinant human α1β2γ2 receptors was similar (IC 50=23.0±1.3 μM) to that observed in rat receptors of the same configuration, indicating the site of action is conserved in the two species. The inhibitory effects were dependent on channel gating, were independent of transmembrane voltage, and were also observed in GABA A receptors recorded from hypothalamic brain slices. The pharmacologic mechanism of inhibition by nitrendipine was non-competitive, indicating it does not act at the GABA binding site. Nitrendipine block was retained in the presence of the benzodiazepine antagonist flumazenil, indicating it does not interact at the benzodiazepine site. The actions of nitrendipine were not affected by a mutation (β2T246F) that confers resistance to the channel blocker picrotoxin, and they were not altered in the presence of the picrotoxin site antagonist α-isopropyl-α-methyl- γ-butyrolactone, demonstrating nitrendipine does not act at the picrotoxin site of the GABAA receptor. Possible interaction of nitrendipine with the Zn++ site was also eliminated, as mutation of β2 H267 to A, which confers resistance to Zn++, had no effect on nitrendipine-mediated inhibition. Our data suggest some of the central effects of dihydropyridines may be due to actions at GABAA receptors. Moreover, the effects may be mediated through interaction with a novel modulatory site on the GABAA receptor.

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KW - Cl channel

KW - Dihydropyridine

KW - L-type Ca channel

KW - Recombinant receptor

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