Study of Interaction Between Oxytocin and Opioid System in Locus Coeruleus on Acute Pain in the Rat

Studies show that the plaus a role hormone oxytocin in the control of pain, sexual behavior, anxiety and love. The mechanism of this neuropeptide is not completely understood in the CNS. This study aimed at researching the effect of oxytoxin administered in the locus coeruleus (LC) nucleus on pain and its interaction with opioid system, because LC influences the nociception and also contains oxytocin and opioid receptors. Male wistar rats weighing 270±20 grams were used. Animals divided to the in control group, receiving only oxytocin (3nmol/2µl) and the group receiving oxytocin (3nmol/2µl) with naloxone as an opioid receptor antagonist (3nmol/1µl) in LC nucleus. Hot plate and tail flick tests were used for pain response evaluations. Oxytocin injection in locus coeruleus nucleus induced analgesic effect significantly in two analgesiometer tests (p<0.001). Naloxone prevented the analgesic effect of oxytocin significantly (Hot plate p<0.001, Tail flick p<0.05). Oxytocin exerts part of its antinociception effect via LC nucleus and probably by excitation of the opioid system because of the inhibiting effect of naloxone.