I1 Receptor Binding Assay: Binding assays were performed at 37° C. using [125I]LNP 911 as radioligand following the general procedure described but adapted to washed whole platelets (Greney, H.; Urosevic, D.; Schann, S.; Dupuy, L.; Bruban, V.; Ehrhardt, J,-D.; Bousquet, P.; Dontenwill, M. [125I]2-(2-Chloro-4-iodo-phenylamino)-5-methyl-pyrroline (LNP911), a High-Affinity Radioligand Selective for I1 Imidazoline Receptors. Mol. Pharmacol. 2002, 62, 181-191).Incubation was initiated through the addition of 900 to 950 ul of platelet suspension at a concentration of 500000/ul in a final volume of 1 ml Tyrode albumin and was performed at 37° C. for 5 min (equilibrium conditions). The competitive assays were conducted using a single concentration of radioligand (50 uM, 200 000 cpm), in the presence of increasing concentrations of suitable non-labelled ligand. Non-specific binding was determined by the binding of [125I]LNP 911 in the presence of 100 nM of non-labelled LNP 911 and represented about 10% of total radioactivity when 50 uM of [125I]LNP 911 were used. The reaction was halted by rapid vacuum filtration through GF/C fibre glass filters followed by five rapid washings of the filters with 3 ml of ice-cold Tyrode (137 nM NaCl, 2.7 nM KCl, 12 nM NaHCO3, 0.36 nM NaH2PO4, pH 7.35). Radioactivity was measured using a gamma counter (Wallac 1410).
Alpha2-Adrenergic Receptor Binding Assay: The membrane preparation was prepared as described by Newman-Tancredi, A.; Nicolas, J,-P.; Audinot, V.; Gavaudan, S.; Verriele, L.; Touzard, M.; Chaput, C.; Richard, N.; Millan, N. J. (Action of alpha2 Adrenoreceptor Ligands at alpha2A and 5-HT1A Receptors: the Antagonist, Atipamezole, and the Agonist, Dexmedetomidine, are Highly Selective for alpha2A Adrenoreceptors. Naunyn-Schmiedeberg's Arch. Pharmacol. 1998, 358, 197-206). These membranes (30 ug proteins/ml for CHO-halpha2A and CHO-halpha2B, 100 ug protein/ml for CHO-halpha2C) were incubated for 60 min at ambient temperature in binding buffer (33 mM Tris-HCl, 1 mM EDTA, pH 7.5) in a final volume of 500 uL containing 0.8 or 1 or 2 nM [3H]RX821002 respectively for the adrenergic receptors halpha2A, halpha2B and halpha2C. Incubation was halted by rapid vacuum filtration through GF/C glass fibre filters followed by three successive washings in ice-cold binding buffer. Non-specific binding was determined using 10 uM phentolamine.