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SR 141716A acts as an inverse agonist to increase neuronal voltage-dependent Ca2+ currents by reversal of tonic CB1 cannabinoid receptor activity.
Mol Pharmacol. 1998 Dec; 54(6):1064-72.MP

Abstract

The CB1 cannabinoid receptor antagonist SR 141716A abolished the inhibition of Ca2+ currents by the agonist WIN 55,212-2. However, SR 141716A alone increased Ca2+ currents, with an EC50 of 32 nM, in neurons that had been microinjected with CB1 cRNA. For an antagonist to elicit an effect, some receptors must be tonically active. Evidence for tonically active CB1 receptors was seen as enhanced tonic inhibition of Ca2+ currents. Preincubation with anandamide failed to enhance the effect of SR 141716A, indicating that anandamide did not cause receptor activity. Under Ca2+-free conditions designed to block the Ca2+-dependent formation of anandamide and sn-2-arachidonylglycerol, SR 141716A again increased the Ca2+ current. The Ca2+ current was tonically inhibited in neurons expressing the mutant K192A receptor, which has no affinity for anandamide, demonstrating that this receptor is also tonically active. SR 141716A had no effect on the Ca2+ current in these neurons, but SR 141716A could still antagonize the effect of WIN 55, 212-2. Thus, the K192 site is critical for the inverse agonist activity of SR 141716A. SR 141716A appeared to become a neutral antagonist at the K192A mutant receptor. Native cannabinoid receptors were studied in male rat major pelvic ganglion neurons, where it was found that WIN 55,212-2 inhibited and SR 141716A increased Ca2+ currents. Taken together, our results demonstrate that a population of native and cloned CB1 cannabinoid receptors can exist in a tonically active state that can be reversed by SR 141716A, which acts as an inverse agonist.

Authors+Show Affiliations

Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, Georgia 30912-2300, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9855635

Citation

Pan, X, et al. "SR 141716A Acts as an Inverse Agonist to Increase Neuronal Voltage-dependent Ca2+ Currents By Reversal of Tonic CB1 Cannabinoid Receptor Activity." Molecular Pharmacology, vol. 54, no. 6, 1998, pp. 1064-72.
Pan X, Ikeda SR, Lewis DL. SR 141716A acts as an inverse agonist to increase neuronal voltage-dependent Ca2+ currents by reversal of tonic CB1 cannabinoid receptor activity. Mol Pharmacol. 1998;54(6):1064-72.
Pan, X., Ikeda, S. R., & Lewis, D. L. (1998). SR 141716A acts as an inverse agonist to increase neuronal voltage-dependent Ca2+ currents by reversal of tonic CB1 cannabinoid receptor activity. Molecular Pharmacology, 54(6), 1064-72.
Pan X, Ikeda SR, Lewis DL. SR 141716A Acts as an Inverse Agonist to Increase Neuronal Voltage-dependent Ca2+ Currents By Reversal of Tonic CB1 Cannabinoid Receptor Activity. Mol Pharmacol. 1998;54(6):1064-72. PubMed PMID: 9855635.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - SR 141716A acts as an inverse agonist to increase neuronal voltage-dependent Ca2+ currents by reversal of tonic CB1 cannabinoid receptor activity. AU - Pan,X, AU - Ikeda,S R, AU - Lewis,D L, PY - 1998/12/18/pubmed PY - 1998/12/18/medline PY - 1998/12/18/entrez SP - 1064 EP - 72 JF - Molecular pharmacology JO - Mol Pharmacol VL - 54 IS - 6 N2 - The CB1 cannabinoid receptor antagonist SR 141716A abolished the inhibition of Ca2+ currents by the agonist WIN 55,212-2. However, SR 141716A alone increased Ca2+ currents, with an EC50 of 32 nM, in neurons that had been microinjected with CB1 cRNA. For an antagonist to elicit an effect, some receptors must be tonically active. Evidence for tonically active CB1 receptors was seen as enhanced tonic inhibition of Ca2+ currents. Preincubation with anandamide failed to enhance the effect of SR 141716A, indicating that anandamide did not cause receptor activity. Under Ca2+-free conditions designed to block the Ca2+-dependent formation of anandamide and sn-2-arachidonylglycerol, SR 141716A again increased the Ca2+ current. The Ca2+ current was tonically inhibited in neurons expressing the mutant K192A receptor, which has no affinity for anandamide, demonstrating that this receptor is also tonically active. SR 141716A had no effect on the Ca2+ current in these neurons, but SR 141716A could still antagonize the effect of WIN 55, 212-2. Thus, the K192 site is critical for the inverse agonist activity of SR 141716A. SR 141716A appeared to become a neutral antagonist at the K192A mutant receptor. Native cannabinoid receptors were studied in male rat major pelvic ganglion neurons, where it was found that WIN 55,212-2 inhibited and SR 141716A increased Ca2+ currents. Taken together, our results demonstrate that a population of native and cloned CB1 cannabinoid receptors can exist in a tonically active state that can be reversed by SR 141716A, which acts as an inverse agonist. SN - 0026-895X UR - https://www.unboundmedicine.com/medline/citation/9855635/SR_141716A_acts_as_an_inverse_agonist_to_increase_neuronal_voltage_dependent_Ca2+_currents_by_reversal_of_tonic_CB1_cannabinoid_receptor_activity_ L2 - http://molpharm.aspetjournals.org/cgi/pmidlookup?view=long&pmid=9855635 DB - PRIME DP - Unbound Medicine ER -