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Endocannabinoid tone versus constitutive activity of cannabinoid receptors.
Br J Pharmacol 2011; 163(7):1329-43BJ

Abstract

This review evaluates the cellular mechanisms of constitutive activity of the cannabinoid (CB) receptors, its reversal by inverse agonists, and discusses the pitfalls and problems in the interpretation of the research data. The notion is presented that endogenously produced anandamide (AEA) and 2-arachidonoylglycerol (2-AG) serve as autocrine or paracrine stimulators of the CB receptors, giving the appearance of constitutive activity. It is proposed that one cannot interpret inverse agonist studies without inference to the receptors' environment vis-à-vis the endocannabinoid agonists which themselves are highly lipophilic compounds with a preference for membranes. The endocannabinoid tone is governed by a combination of synthetic pathways and inactivation involving transport and degradation. The synthesis and degradation of 2-AG is well characterized, and 2-AG has been strongly implicated in retrograde signalling in neurons. Data implicating endocannabinoids in paracrine regulation have been described. Endocannabinoid ligands can traverse the cell's interior and potentially be stored on fatty acid-binding proteins (FABPs). Molecular modelling predicts that the endocannabinoids derived from membrane phospholipids can laterally diffuse to enter the CB receptor from the lipid bilayer. Considering that endocannabinoid signalling to CB receptors is a much more likely scenario than is receptor activation in the absence of agonist ligands, researchers are advised to refrain from assuming constitutive activity except for experimental models known to be devoid of endocannabinoid ligands.

Authors+Show Affiliations

Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA. ahowlett@wfubmc.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Review

Language

eng

PubMed ID

21545414

Citation

Howlett, Allyn C., et al. "Endocannabinoid Tone Versus Constitutive Activity of Cannabinoid Receptors." British Journal of Pharmacology, vol. 163, no. 7, 2011, pp. 1329-43.
Howlett AC, Reggio PH, Childers SR, et al. Endocannabinoid tone versus constitutive activity of cannabinoid receptors. Br J Pharmacol. 2011;163(7):1329-43.
Howlett, A. C., Reggio, P. H., Childers, S. R., Hampson, R. E., Ulloa, N. M., & Deutsch, D. G. (2011). Endocannabinoid tone versus constitutive activity of cannabinoid receptors. British Journal of Pharmacology, 163(7), pp. 1329-43. doi:10.1111/j.1476-5381.2011.01364.x.
Howlett AC, et al. Endocannabinoid Tone Versus Constitutive Activity of Cannabinoid Receptors. Br J Pharmacol. 2011;163(7):1329-43. PubMed PMID: 21545414.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Endocannabinoid tone versus constitutive activity of cannabinoid receptors. AU - Howlett,Allyn C, AU - Reggio,Patricia H, AU - Childers,Steven R, AU - Hampson,Robert E, AU - Ulloa,Nadine M, AU - Deutsch,Dale G, PY - 2011/5/7/entrez PY - 2011/5/7/pubmed PY - 2012/1/19/medline SP - 1329 EP - 43 JF - British journal of pharmacology JO - Br. J. Pharmacol. VL - 163 IS - 7 N2 - This review evaluates the cellular mechanisms of constitutive activity of the cannabinoid (CB) receptors, its reversal by inverse agonists, and discusses the pitfalls and problems in the interpretation of the research data. The notion is presented that endogenously produced anandamide (AEA) and 2-arachidonoylglycerol (2-AG) serve as autocrine or paracrine stimulators of the CB receptors, giving the appearance of constitutive activity. It is proposed that one cannot interpret inverse agonist studies without inference to the receptors' environment vis-à-vis the endocannabinoid agonists which themselves are highly lipophilic compounds with a preference for membranes. The endocannabinoid tone is governed by a combination of synthetic pathways and inactivation involving transport and degradation. The synthesis and degradation of 2-AG is well characterized, and 2-AG has been strongly implicated in retrograde signalling in neurons. Data implicating endocannabinoids in paracrine regulation have been described. Endocannabinoid ligands can traverse the cell's interior and potentially be stored on fatty acid-binding proteins (FABPs). Molecular modelling predicts that the endocannabinoids derived from membrane phospholipids can laterally diffuse to enter the CB receptor from the lipid bilayer. Considering that endocannabinoid signalling to CB receptors is a much more likely scenario than is receptor activation in the absence of agonist ligands, researchers are advised to refrain from assuming constitutive activity except for experimental models known to be devoid of endocannabinoid ligands. SN - 1476-5381 UR - https://www.unboundmedicine.com/medline/citation/21545414/Endocannabinoid_tone_versus_constitutive_activity_of_cannabinoid_receptors_ L2 - https://doi.org/10.1111/j.1476-5381.2011.01364.x DB - PRIME DP - Unbound Medicine ER -