Cannabinoids inhibit N-type calcium channels in neuroblastoma-glioma cells.
The psychoactive properties of Cannabis sativa and its major biologically active constituent, delta 9-tetrahydrocannabinol, have been known for years. The recent identification and cloning of a specific cannabinoid receptor suggest that cannabinoids mimic endogenous compounds affecting neural signals for mood, memory, movement, and pain. Using whole-cell voltage clamp and the cannabinomimetic aminoalkylindole WIN 55,212-2, we have found that cannabinoid receptor activation reduces the amplitude of voltage-gated calcium currents in the neuroblastoma-glioma cell line NG108-15. The inhibition is potent, being half-maximal at less than 10 nM, and reversible. The inactive enantiomer, WIN 55,212-3, does not reduce calcium currents even at 1 microM. Of the several types of calcium currents in NG108-15 cells, cannabinoids predominantly inhibit an omega-conotoxin-sensitive, high-voltage-activated calcium current. Inhibition was blocked by incubation with pertussis toxin but was not altered by prior treatment with hydrolysis-resistant cAMP analogues together with a phosphodiesterase inhibitor, suggesting that the transduction pathway between the cannabinoid receptor and calcium channel involves a pertussis toxin-sensitive GTP-binding protein and is independent of cAMP metabolism. However, the development of inhibition is considerably slower than a pharmacologically similar pathway used by an alpha 2-adrenergic receptor in these cells. Our results suggest that inhibition of N-type calcium channels, which could decrease excitability and neurotransmitter release, may underlie some of the psychoactive effects of cannabinoids.
Mackie
K
K
Department of Anesthesiology, University of Washington School of Medicine, Seattle 98195.
Hille
B
B
D000818:Animals; D048588:Benzoxazines; D015220:Calcium Channels / Q000187:drug effects*; D002186:Cannabinoids / Q000494:pharmacology*; D004553:Electric Conductivity; D005910:Glioma; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009447:Neuroblastoma; D009638:Norepinephrine / Q000494:pharmacology; D037342:Pertussis Toxin; D051381:Rats; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000502:physiology*; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D048588:Benzoxazines; D015220:Calcium Channels; D002186:Cannabinoids; D009025:Morpholines; D009281:Naphthalenes; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D010566:Virulence Factors, Bordetella; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D037342:Pertussis Toxin; D009638:Norepinephrine