BACKGROUND:

Previous studies have demonstrated the participation of peripheral µ-opioid receptors (MOR) in the antinociceptive effect of systemically administered morphine and loperamide in an orofacial muscle pain model, induced by hypertonic saline, but not in a spinally innervated one, in rats. In this study, we determine whether this peripheral antinociceptive effect is due to the activation of MOR localized in the muscle, ganglia, or both.

METHODS:

To determine the local antinociceptive effect of morphine and loperamide, 2 models of acute muscle pain (trigeminal and spinal) were used. Also, to study the MOR expression, protein quantification was performed in the trigeminal and spinal ganglia, and in the muscles.

RESULTS:

The behavioral results show that the intramuscular injection of morphine and loperamide did not exert an antinociceptive effect in either muscle (morphine P = .63, loperamide P = .9). On the other hand, MOR expression was found in the ganglia but not in the muscles. This expression was on average 44% higher (95% confidence interval, 33.3-53.9) in the trigeminal ganglia than in the spinal one.

CONCLUSIONS:

The peripheral antinociceptive effect of systemically administered opioids may be due to the activation of MOR in ganglia. The greater expression of MOR in trigeminal ganglia could explain the higher antinociceptive effect of opioids in orofacial muscle pain than in spinal muscle pain. Therefore, peripheral opioids could represent a promising approach for the treatment of orofacial pain.

Assuntos

Dor Aguda/tratamento farmacológico Analgésicos/farmacologia Dor Facial/tratamento farmacológico Gânglios Espinais/efeitos dos fármacos Loperamida/farmacologia Morfina/farmacologia Mialgia/tratamento farmacológico Receptores Opioides mu/efeitos dos fármacos Gânglio Trigeminal/efeitos dos fármacos Dor Aguda/metabolismo Dor Aguda/fisiopatologia Animais Modelos Animais de Doenças Dor Facial/metabolismo Dor Facial/fisiopatologia Gânglios Espinais/metabolismo Gânglios Espinais/fisiopatologia Masculino Músculo Esquelético/efeitos dos fármacos Músculo Esquelético/metabolismo Mialgia/metabolismo Mialgia/fisiopatologia Ratos Wistar Receptores Opioides mu/metabolismo Gânglio Trigeminal/metabolismo Gânglio Trigeminal/fisiopatologia

BVS Odontologia

Informação e Conhecimento para a Saúde

Formato de exportação:

Mu-Opioid Receptors in Ganglia, But Not in Muscle, Mediate Peripheral Analgesia in Rat Muscle Pain.

BACKGROUND:

METHODS:

RESULTS:

CONCLUSIONS:

Assuntos