Fig. 1.

CP55,940 and WIN55,212-2 differ in their abilities to internalize rCB₂ but not rCB₁ cannabinoid receptors. A, In rCB₁- and rCB₂-expressing HEK293 cells, 100 nM CP55,940 results in receptor internalization (n = 6–26 for each time point). B, 2 h of exposure to CP55,940 internalized rCB₁ and rCB₂ in a concentration-dependent manner (n = 3–26 for each concentration). C, 1 μM rimonabant (Rim) and 1 μM AM630 prevent receptor internalization by 100 nM CP55,940 treatment in rCB₁ (n = 3) and rCB₂ cells (n = 10), respectively. D, 100 nM WIN55,212-2 results in robust rCB₁ but not rCB₂ receptor internalization (n = 7–11). E, 2 h of exposure to WIN55,212-2 internalized rCB₁ in a concentration-dependent manner but not rCB₂ (n = 4–6). F, 1 μM rimonabant prevents receptor internalization by 100 nM WIN55,212-2 (WIN) treatment in rCB₁ (n = 5) but AM630 does not alter the effect of WIN55,212-2 on rCB₂ cells (n = 4). G, representative images of rCB₁ and rCB₂ cells treated with 100 nM CP55,940 or 100 nM WIN55,212-2 for 2 h. Cotreatment with 1 μM rimonabant and 1 μM AM630 is also shown. Scale bars, 20 μm. Data in A through F analyzed using unpaired Student's t tests. *, p < 0.05; **, p < 0.01; ***, p < 0.001.