Effects of single administration of morphine on G-protein mRNA level in the presence and absence of inflammation in the rat spinal cord.

Antinociceptive potency of opioids is greater against various noxious stimuli in animals with peripheral inflammation. Opioid agonists stimulate activation of G-protein-coupled receptor. Changes in the resting levels of G-protein subtypes could have an effect on intracellular signalling pathways. The present study was designed to investigate the effects of analgesic morphine treatment on the level G-protein subunits mRNA in the presence and absence of inflammation. Our results showed that the carrageenan administration increased G-protein subunits. Administration of analgesic dose of morphine alone and in the presence of inflammation induced different alterations in the levels of G-protein mRNA. Taken together, the results obtained using real time RT-PCR suggested that G-protein genes expression levels following the acute administration of morphine between animals with and without inflammation could influence, at least in part, analgesic responsiveness.