Cannabinoids inhibit N-type calcium channels in neuroblastoma-glioma cells.

TLDR

Cannabis sativa’s psychoactive effects are mediated by delta‑9‑tetrahydrocannabinol, and the discovery of a specific cannabinoid receptor indicates that cannabinoids modulate neural signaling involved in mood, memory, movement, and pain. Whole‑cell voltage‑clamp recordings in NG108‑15 cells showed that activation of cannabinoid receptors by WIN 55,212‑2 reduces voltage‑gated calcium currents. WIN 55,212‑2 potently (IC50 < 10 nM) and reversibly inhibits omega‑conotoxin‑sensitive N‑type calcium currents in NG108‑15 cells via a pertussis‑toxin‑sensitive G protein pathway independent of cAMP, and this inhibition may contribute to cannabinoids’ psychoactive actions.

Abstract

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.