Characterization of CB1 Receptors on Rat Neuronal Cell Cultures: Binding and Functional Studies Using the Selective Receptor Antagonist SR 141716A |
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Authors: | M Jung R Calassi M Rinaldi-Carmona P Chardenot G Le Fur P Soubrié F Oury-Donat |
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Institution: | Sanofi Recherche, Montpellier, France |
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Abstract: | Abstract: This study was undertaken to characterize further the central cannabinoid receptors in rat primary neuronal cell cultures from selected brain structures. By using 3H]SR 141716A, the specific CB1 receptor antagonist, we demonstrate in cortical neurons the presence of a high density of specific binding sites ( B max = 139 ± 9 fmol/mg of protein) displaying a high affinity ( K D = 0.76 ± 0.09 n M ). The two cannabinoid receptor agonists, CP 55940 and WIN 55212-2, inhibited in a concentration-dependent manner cyclic AMP production induced by either 1 µ M forskolin or isoproterenol with EC50 values in the nanomolar range (4.6 and 65 n M with forskolin and 1.0 and 5.1 n M with isoproterenol for CP 55940 and WIN 55212-2, respectively). Moreover, in striatal neurons and cerebellar granule cells, CP 55940 was also able to reduce the cyclic AMP accumulation induced by 1 µ M forskolin with a potency similar to that observed in cortical neurons (EC50 values of 3.5 and 1.9 n M in striatum and cerebellum, respectively). SR 141716A antagonized the CP 55940- and WIN 55212-2-induced inhibition of cyclic AMP accumulation, suggesting CB1 receptor-specific mediation of these effects on all primary cultures tested. Furthermore, CP 55940 was unable to induce mitogen-activated protein kinase activation in either cortical or striatal neurons. In conclusion, our results show nanomolar efficiencies for CP 55940 and WIN 55212-2 on adenylyl cyclase activity and no effect on any other signal transduction pathway investigated in primary neuronal cultures. |
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Keywords: | CB1 receptors SR 141716A Cyclic AMP Mitogen-activated protein kinase Primary neuronal cell cultures |
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