Table 3.
Functional expression of the NOP receptor in rodent nociceptive system and effects of N/OFQ and non-peptide NOP receptor agonists under conditions of neuropathic pain
| NOP receptor expression | Function of N/OFQ and NOP receptor agonists | |||||
|---|---|---|---|---|---|---|
| Region | mRNA | Protein | In vitro | In vivo | ||
| Supraspinal | Thalamus | |||||
| Amygdala | ||||||
| PAG | Up-regulated 7–14 days after CCI [ISH] (Ma et al., 2005) | Endogenous N/OFQ tone maintained, since m.i. UFP-101, inhibited mechanical allodynia [CCI rat] (Scoto et al., 2009) | i.c.v. GRT-TA2210, Ro65-6570: ↓ cold allodynia [CCI mouse] (Linz et al., 2013) | |||
| RVM | Up-regulated 7–14 days after CCI [ISH] (Ma et al., 2005) | |||||
| Spinal | Intrinsic neurons | Up-regulated in lumbar enlargement 7 days after CCI [RT-PCR] (Briscini et al., 2002) | i.t.: ↓ thermal hyperalgesia [partial sciatic nerve injury rat, CCI rat] (Yamamoto and Nozaki-Taguchi, 1997; Yamamoto et al., 1997c) | |||
| i.t.: ↓ mechanical and cold allodynia [sciatic nerve injury rat] (Hao et al., 1998) | ||||||
| i.t.: ↓ flexor reflex [sciatic nerve transection rat] (Xu et al., 1999) | ||||||
| i.t.: antinociceptive in diabetic poly-neuropathy [tail flick mouse] (Kamei et al., 1999) | ||||||
| i.t.: ↓ mechanical allodynia and hyperalgesia [CCI rat] (Corradini et al., 2001; Briscini et al., 2002; Courteix et al., 2004) | ||||||
| i.t.: synergistic interaction with i.t. morphine to suppress mechanical hyperalgesia [CCI rat] (Courteix et al., 2004) | ||||||
| Proximal PAF (presynaptic) | i.t.: ↓ spontaneous and mechanically evoked activity of lamina V WDR neurons [CCI rat] (Sotgiu et al., 2004) | |||||
| i.t. Ro64-6198, N/OFQ: ↓ mechanical and cold allodynia [CCI rat] (Obara et al., 2005) | ||||||
| i.t.: ↓ mechanical allodynia [SNL rat] (Ju et al., 2013) i.t. GRT-TA2210, Ro65-6570: ↓ cold allodynia [CCI mouse] (Linz et al., 2013) | ||||||
| Peripheral | DRG neuron (cell body) | Up-regulated in L5-L6 7 days after CCI [RT-PCR] (Briscini et al., 2002) | Up-regulated 7 days after sciatic nerve injury [IHC] (Chen and Sommer, 2006) | ↑ inhibition of N-type Ca2+ current after sciatic nerve section [patch clamp] (Abdulla and Smith, 1998) | ||
| Distal PAF (dendritic) | i.pl. Ro64-6198, N/OFQ: ↓ mechanical and cold allodynia [CCI rat] (Obara et al., 2005) | |||||
No data are published for fields that are left blank. ↑, activation/increase; ↓, inhibition/decrease; GRT-TA2210, selective NOP receptor agonist; IHC, immunohistochemistry; ISH, in situ hybridization; m.i., microinjected; PAF, primary afferent fibre; Ro64-6198, Ro65-6570, selective NOP receptor agonists; UFP-101, selective NOP receptor antagonist.