TABLE 1.
Summary of effects of mu (MOR), delta (DOR), and kappa (KOR) opioid receptor activation on neuronal excitability (postsynaptic effects), presynaptic GABA release, and presynaptic glutamate release.
| Postsynaptic effects |
Presynaptic GABA |
Presynaptic Glutamate |
|||||||
| MOR | DOR | KOR | MOR | DOR | KOR | MOR | DOR | KOR | |
| Amygdala | |||||||||
| BLA | – | + | ± | ± | – | ||||
| BNST | + | + | ± | ||||||
| CeA | ± | ± | ± | + | ± | + | + | ± | ± |
| MICR | + | ± | ± | – | |||||
| Brainstem/Midbrain | |||||||||
| DVM | ± | + | |||||||
| LC | + | + | + | ||||||
| MVN | – | + | – | ||||||
| NTS | + | – | – | ± | + | + | |||
| PAG | ± | ± | + | ± | ± | + | – | – | |
| Pons | + | – | – | + | + | + | + | – | – |
| Raphe | ± | ± | + | – | – | + | + | ||
| RVM | ± | ± | ± | ± | ± | ± | |||
| SN | + | + | + | + | + | ||||
| VTA/RMTg | ± | ± | ± | + | ± | + | + | + | |
| Cortex | |||||||||
| ACC | ± | ± | – | + | ± | + | |||
| AIC | ± | ± | ± | ||||||
| mPFC | + | ± | ± | ± | |||||
| OFC | ± | ||||||||
| S1 | ± | ± | ± | ||||||
| Hippocampus | |||||||||
| CA1 | ± | ± | ± | ± | ± | – | – | ||
| CA2 | + | ||||||||
| CA3 | ± | ± | + | – | – | ± | + | ||
| DG | + | + | + | + | + | + | ± | – | ± |
| Hypothalamus | |||||||||
| AN | ± | ± | ± | + | ± | + | + | – | + |
| LH | + | ||||||||
| PO | + | + | |||||||
| PVN | + | + | + | ||||||
| SON | ± | ± | ± | ± | ± | + | ± | ||
| VMH | + | – | – | + | – | + | |||
| Habenula | |||||||||
| LHb | ± | ± | + | ± | + | ||||
| Pallidum | |||||||||
| GP | + | – | ± | + | ± | + | – | ||
| EPN | + | + | |||||||
| VP | + | + | + | + | + | ||||
| Striatum | |||||||||
| DS | – | – | ± | ± | ± | ± | + | ||
| NAc | ± | ± | ± | + | ± | ± | |||
| Thalamus | |||||||||
| Thalamus | + | – | ± | ||||||
+, Identified effects of opioid receptor activation.
–, Identified null effect of opioid receptor activation.
±, Identified effects in a subpopulation of neurons or inconsistent results between studies.
Blanks indicate untested areas. Note that future studies may reveal heterogenous responses to opioid receptor activation where past studies have either observed widespread effects or null effects.