Table 1. The binding affinities of ketamine and psilocin for various receptor types.
| Ki values, binding affinity (nM) | |||
|---|---|---|---|
| Ketamine | Psilocin | Radioligand | |
| 5-HT1A | Low affinity | 567 | [3H]-8-OH-DPAT |
| 5-HT1B | Low affinity | 220 | [3H]-GR-125743 |
| 5-HT1D | Low affinity | 36 | [3H]-GR-125743 |
| 5-HT1E | Low affinity | 52 | [3H]-5HT |
| 5-HT2A | Low affinity | 107 | [3H]-Ketanserin |
| 5-HT2B | Low affinity | 5 | [3H]-LSD |
| 5-HT2C | Low affinity | 97a | [3H]-Mesulergine |
| 5-HT3 | Low affinity | Low affinity | [3H]-LY 278584 |
| 5-HT5 | Low affinity | 84 | [3H]-LSD |
| 5-HT6 | Low affinity | 57 | [3H]-LSD |
| 5-HT7 | Low affinity | 4 | [3H]-LSD |
| 5-HT transporter | N.A. | 3,801 | [3H]-Citalopram |
| NMDA | 661a | N.A. | [3H]-MK-801 |
| Adrenergic α2A | Low affinity | 1,379 | Ketamine: [3H]-Rauwolscine; Psilocin: [125I]-Clonidine |
| Adrenergic α2B | Low affinity | 1,894 | Ketamine: [3H]-Rauwolscine; Psilocin: [125I]-Clonidine |
| Dopamine D3 | Low affinity | 2,645a | Ketamine: [3H]-N-Methylspiperone; Psilocin: [3H]-NMSP |
| Histamine H1 | Low affinity | 305 | [3H]-Pyrilamine |
Low affinity, Ki >10,000 nM
N.A., not available
Source: NIMH Psychoactive Drug Screen Program (PDSP) [129]. Ki values are PDSP certified values (human data except where a indicates value from rats when human data were unavailable). Note that values for ketamine are for the racemic mixture, which consists of (S)- and (R)-ketamine that are converted into multiple metabolites. The enantiomers and metabolites have varying affinities to NMDAR and other receptors [22].