Table 2.
Meta-analytic Kd values for radioligands at human (Hs) and rat (Rn) cannabinoid receptors
| Radioligand | HsCB1 | RnCB1 | HsCB2 | RnCB2 | HsCB1 | HsCB2 | RnCB1 | RnCB2 |
|---|---|---|---|---|---|---|---|---|
| Kd±s.e. | Kd±s.e. | Kd±s.e. | Kd±s.e. | Kd±s.e. | Kd±s.e. | Kd±s.e. | Kd±s.e. | |
| [3H]CP55,940 | 2.5±0.39 (n=28) | 0.98±0.12 (n=51) | 0.92±0.16 (n=18) | 0.84±0.30 (n=8) | 2.5±0.39 (n=28) | 0.92±0.16 (n=18) | 0.98±0.12 (n=51) | 0.84±0.30 (n=8) |
| Difference between species, P=0.001; Kd ratio=2.6 | No difference, P=0.32; Kd ratio=1.1 | Difference between CB1 and CB2, P=0.001; Kd ratio=2.7 | No difference, P=0.19; Kd ratio=1.2 | |||||
| [3H]WIN55212 | 16.7±1.71 (n=6) | 2.4±0.348 (n=13) | 3.7±1.19 (n=7) | 35.6 (n=2) | 16.7±1.71 (n=6) | 3.7±1.19 (n=7) | 2.4±0.348 (n=13) | ND |
| Difference between species, P=0.001; Kd ratio=7.0 | Difference between CB1 and CB2, P=0.003; Kd ratio=4.5 | |||||||
| [3H]SR141716A | 2.9±0.54 (n=10) | 1.0±0.22 (n=19) | ND | ND | 2.9±0.54 (n=10) | ND | 1.0±0.22 (n=19) | ND |
| Difference between species, P=0.002; Kd ratio=2.9 | ||||||||
Abbreviations: Hs, Homo sapiens; Rn, Rattus norvegicus.
The results in the table are expressed as Kd±s.e. (nM) and the number of studies extracted for determination of pooled means. Means in bold typeface had their numerical validity confirmed by sensitivity analyses. Differences between validated means were tested for statistical significance with Mann–Whitney U-test (Systat; Evanston, IL, USA). ND=no Kd data in Supplementary Table 1.