The stimulatory effect of cannabinoids on calcium uptake is mediated by Gs GTP-binding proteins and cAMP formation.
Cannabinoids are neurodepressive drugs that convey their cellular action through G(i/o) GTP-binding proteins which reduce cAMP formation and Ca(2+) influx. However, a growing body of evidence indicates that the stimulatory effects of cannabinoids include the elevation in cAMP and cytosolic Ca(2+) concentration. The present study expands our previous findings and demonstrates that, in N18TG2 neuroblastoma cells, the cannabinoid agonist desacetyllevonantradol (DALN) stimulates both cAMP formation and Ca(2+) uptake. The stimulatory effect of DALN on cAMP formation was not eliminated by blocking Ca(2+) entry to the cells, while its stimulatory effect on Ca(2+) uptake was abolished by blocking cAMP-dependent protein kinase. Furthermore, elevating cAMP by forskolin stimulated calcium uptake, while elevating the intracellular Ca(2+) concentration by ionomycin or KCl failed to stimulate cAMP formation. These findings suggest that cAMP production precedes the influx of Ca(2+) in the cannabinoid stimulatory cascade. The stimulatory effect of DALN on calcium uptake resisted pertussis toxin treatment, and was completely blocked by introducing anti-G(s) antibodies into the cells, indicating that the stimulatory activity of cannabinoids is mediated by G(s) GTP-binding proteins. The relevance of the cellular stimulatory activity of DALN to the pharmacological profile of cannabinoid drugs is discussed.
Bash
Roni
R
Mauerberger Chair in Neuropharmacology, Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
Rubovitch
Vardit
V
Gafni
Mikhal
M
Sarne
Yosef
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002186:Cannabinoids / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D014407:Tumor Cells, Cultured
D002186:Cannabinoids; D000242:Cyclic AMP; D019205:GTP-Binding Protein alpha Subunits, Gs; D002118:Calcium