title: Effects of intra-fourth ventricle injection of crocin on capsaicin-induced orofacial pain in rats.
abstract: OBJECTIVE
  Crocin, a constituent of saffron and yellow gardenia, possesses anti-nociceptive effects. In the present study, we investigated the effects of intra-fourth ventricle injection of crocin in a rat model of orofacial pain. The contribution of opioid system was assessed using intra-fourth ventricle injection of naloxone, an opioid receptor antagonist.
  
  
  METHODS
  A guide cannula was implanted into the fourth ventricle of brain in anesthetized rats. Orofacial pain was induced by subcutaneous (s.c.) injection of capsaicin (1.5 µg/20 µl) into the right vibrissa pad. The time spent face rubbing/grooming was recorded for a period of 20 min. Locomotor activity was measured using an open-field test.
  
  
  RESULTS
  Intra-fourth ventricle injection of crocin (10 and 40 µg/rat) and morphine (10 and 40 µg/rat) and their co-administration (2.5 and 10 µg/rat of each) suppressed capsaicin-induced orofacial pain. The analgesic effect induced by 10 µg/rat of morphine, but not crocin (10 µg/rat), was prevented by 20 µg/rat of naloxone pretreatment. The above-mentioned chemical compounds did not affect locomotor activity.
  
  
  CONCLUSIONS
  The results of this study showed that the injection of crocin into the cerebral fourth ventricle attenuates capsaicin-induced orofacial pain in rats. The anti-nociceptive effect of crocin was not attributed to the central opioid receptors.
authors.affiliation: Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
authors.forename: Esmaeal
authors.initials: E
authors.lastname: Tamaddonfard
authors.affiliation: Faculty of Veterinary Medicine, Urmia Azad University, Urmia, Iran.
authors.forename: Sina
authors.initials: S
authors.lastname: Tamaddonfard
authors.affiliation: Faculty of Veterinary Medicine, Urmia Azad University, Urmia, Iran.
authors.forename: Salar
authors.initials: S
authors.lastname: Pourbaba
keywords: Crocin; Morphine; Naloxone; Orofacial pain; Rats