RT journal article
T1 Behavioral effects of combined morphine and MK-801 administration to the locus coeruleus of a rat neuropathic pain model
A1 Llorca Torralba, Meritxell
A1 Micó Segura, Juan Antonio
A1 Berrocoso Domínguez, Esther María
A2 Neurociencias
A2 Psicología
K1 Locus coeruleus
K1 MK-801
K1 Morphine
K1 Neuropathic pain
AB The persistent activation of N-methyl-d-aspartate acid receptors (NMDARs) seems to be responsible for a series of changes in neurons associated with neuropathic pain, including the failure of opioids that act through mu-opioid receptors (MORs) to provide efficacious pain relief. As the noradrenergic locus coeruleus (LC) forms part of the endogenous analgesic system, we explored how intra-LC administration of morphine, a MORs agonist, alone or in combination with MK-801, a NMDARs antagonist, affects the sensorial and affective dimension of pain in a rat model of neuropathic pain; chronic constriction injury (CCI). Intra-LC microinjection of morphine induced analgesia in CCI rats, as evident in the von Frey and cold plate test 7 and 30 days after surgery, although it was not able to reverse pain-related aversion when evaluated using the place escape/avoidance test. However, the thermal anti-nociception produced by morphine was enhanced when it was administered to the LC of CCI animals in combination with MK-801, without altering its effects on the mechanical thresholds. Furthermore, pain-related aversion was reduced by co-administration of these agents, yet only in the short-term CCI (7 day) rats. Overall the data indicate that administration of morphine to the LC produces analgesia in nerve injured animals and that this effect is potentiated in specific pain modalities by the co-administration of MK-801. While a combination of morphine and MK-801 could reduce pain-related aversion in short-term neuropathic animals, it was ineffective in the long-term, suggesting that its sensorial effects and its influence on the affective component of pain are regulated by different mechanisms.
PB Elsevier
SN 1878-4216
YR 2018
FD 2018-06-08
LK http://hdl.handle.net/10498/33326
UL http://hdl.handle.net/10498/33326
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 08-nov-2026