AMBIENT TEMPERATURE INFLUENCE TO THE ACTIVITY OF THE LIGANDS AND BLOCKERS OF OPIOID RECEPTORS.
Emelyanova T.G.1, Guzevatykh L.S.1, Valuiskykh D.V.1, Andreeva L.A.2, Myasoedov N.F.2.
1Semenov’s Institute of Chemical Physics RAS, Moscow, Russia; email@example.com
2Institute of Molecular Genetics RAS, Moscow, Russia.
It is known that an important factor influencing the sensitivity to pain is the temperature (Strigo et al., 2000). But to this day, the nature of this phenomenon are not fully understood. Some researchers believe that the analgesia caused by cold or warm (LaBuda et al., 2000; Strigo et al., 2000) has opioid nature, others - insist on a non-opioid nature (Osgood et al., 1990).
The purpose of this study was to investigate the influence of ambient temperature on the analgesic activity of the ligands of μ-, - and κ-opioid receptors (dermorphine (DM), metenkephaline and dynorphine A respectively) and the blockers of μ-, - and κ-opioid receptors (naloxone, naltrindole and norbinaltorfimine respectively), and proline’s analogues dermorphine have more analgesic activity than DM (Guzevatykh et al, 2005) and its C-terminal fragments. Research is being done on the model of non-thermal pain ("writhing" test). Peptides and blockers were injected intraperitoneally at doses of 1 and 10 mg / kg.
Research results showed that: 1) pain sensitivity is dependent on the ambient temperature in which the animals were. Low and high ambient temperatures cause it to decrease; 2) blockers μ-, - and κ-opioid receptors - reduce the analgesic effect of heat and cold; 3) DM - selective ligand μ-opioid receptors, has analgesic activity, independently of the ambient temperature. Analgesic effect of metenkephaline and dynorphine A decreases with increasing or decreasing the ambient temperature; 4) proline’s analogues of DM on a hot environment lose their analgesic activity; 5) C-terminal fragments of DM show analgesic activity eliminate naloxone on the thermoneutral environment, whereas cold and hot environments - reduce the analgesic effect of cold and heat. In the cold environment naloxone does not affect the activity of DM5-6 and DM5-7, but potentiates the effect of [DPro6]-DM5-7. In a hot environment naloxone potentiates the analgesic activity of all C-terminal fragments.
Thus, the results of the research showed that ambient temperature has an effect on the efficiency of the ligands and blockers of opioid receptors, indicating the involvement of opioid system in the antinociceptive activity of heat and cold.