Clinical studies suggest that essential oil of Eugenia caryophyllata (Clove) buds (EOEC) is efficacious in the treatment of dental pain. In the present study, we investigated the analgesic and local anesthetic effects of EOEC and its possible mechanisms of action in acute corneal pain in rats. EOEC was extracted by hydro-distillation in a Clevenger type apparatus from clove buds. The acute corneal pain was induced by applying a drop (40 µl) of 5 M NaCl solution on the corneal surface, and the numbers of eye wipes were counted during the first 30 s. The mechanical sensation of the cornea was evaluated by calibrated Von Frey filaments. Systemic administration of EOEC (100 and 200 mg/kg, SC) and morphine (2.5 and 5 mg/kg, IP) produced a significant antinociceptive effect in acute corneal pain. Pretreatment with naloxone or atropine prevented the EOEC-induced analgesia. However, L-arginine and methylene blue did not change the suppressive effect of EOEC on corneal pain response. Topical application of EOEC, eugenol and lidocaine significantly decreased corneal sensitivity. Combination treatments of eugenol (25 µg) with lidocaine (0.5%) and EOEC (50 µg) with lidocaine (0.5%) also significantly suppressed corneal sensitivity. Systemic administration of EOEC produced analgesia in the acute corneal pain through mechanisms that involved both opioidergic and cholinergic systems. In addition, topical instillation of EOEC, eugenol, and lidocaine produced local anesthesia in the rat cornea. Sub-anesthetic doses of EOEC or eugenol produced a significant local anesthetic effect when concurrently used with the sub-anesthetic dose of lidocaine.
This study aimed to assess the effect of intra-habenular injection of morphine on acute trigeminal pain in rats. Also here, we examined the involvement of raphe nucleus opioid and 5HT3 receptors on the antinociceptive activity of intra habenular morphine to explore the possibility of existence of descending antinociceptive relay between the habenula and raphe nucleus. The numbers of eye wiping response elicited by applying a drop (40 μL) of NaCl (5 M) solution on the corneal surface were taken as an index of acute trigeminal nociception. Intra habenular microinjection of morphine at a dose of 2 μg was without effect, whereas at doses of 5 and 8 μg significantly produced antinociception. Microinjection of naltrexone (4 μg) and ondansetron (1 μg) into the dorsal raphe nucleus prior to intra-habenular saline did not produce any significant effect on corneal pain perception. Pretreatment of the raphe nucleus with ondansetron but not naltrexone prevented intra habenular morphine (8 μg) induced antinociception. Also, intra habenular injection of lidocaine (2%, 0.5 μL reduced corneal pain response. Moreover, intra-habenular microinjection of L-glutamic acid (1 and 2 μg/site) did not produce any analgesic activity in this model of pain. In conclusion, the present results suggest that the activation of the habenular μ opioid receptor by microinjection of morphine or inhibition of habenular neurons by microinjection of lidocaine produced an analgesic effect in the acute trigeminal model of pain in rats. The analgesic effect of intra habenular morphine was blocked by intra-dorsal raphe injection of serotonin 5-HT3 antagonist.
Background and Aims: Starting from the cytotoxic effects of monosodium glutamate (MSG), the aim of this study was to evaluate the protective effects of quince leaf extract as natural antioxidant on the reproductive dysfunction induced by monosodium glutamate in rats. Material and methods: Monosodium glutamate was administrated with a dose of 30 and 60 mg/kg and quince leaf extract was administrated with a dose of 500 mg/kg. At the end of study, body and testicular weight measurement, hormonal and epididymal sperm analysis were performed. Results: Follicle stimulating hormone (FSH) and testosterone levels were reduced after administration of monosodium glutamate. The levels of luteinizing hormone (LH) exhibited no significant changes. Treatment with quince leaf extract led to improvement in follicle stimulating hormone and testosterone levels. Epididymal sperm population was reduced after administration of monosodium glutamate and treatment with quince leaf extract. The increased sperm motility rate induced by monosodium glutamate was reduced after treatment with quince leaf extract. Administration of monosodium glutamate led to more body weight gain in comparison to combined administration monosodium glutamate and quince leaf extract. Conclusions: The quince leaf extract can be effective in reduction of functional alterations of reproductive system induced by monosodium glutamate.
The effects of neuropathic, formalin, and acetic acid‐induced visceral pain were investigated on the social and aggressive behaviors in the Swiss male mice. Neuropathic pain was induced by tibial nerve transection (TNT). Also, somatic and visceral pain was conducted by intraplantar injection of diluted formalin (1%, 20 μl) and intraperitoneal administration of acetic acid (0.6%, 200 μl), respectively. Fourteen and twenty one days after the TNT surgery, and also, 1 and 7 days following formalin and acetic acid administration, the three‐chambered test was used to determine sociability and preference for social novelty and resident/intruder test was used for the evaluation of the aggressive behaviors. In the sociability phase of the three‐chambered test, all the three models of pain did not change the animal's sociability. However, in the social novelty preference phase, the animals in pain showed deficits in social novelty preference by a significant increase in the time spent with the familiar mice compared to the control groups. Also, animals in pain significantly showed more aggressive behaviors like biting and clinching and have much less attack latency in comparison to the control groups. Pain‐induced changes in the social novelty preference and aggressive behaviors continued in the neuropathic group until the end of the experiment. However, 7 days following the induction of both formalin and visceral pain, animals' social memory, and aggression almost returned to the standard value. These results suggest that long‐lasting pain could lead to social memory impairment and increase aggressive behaviors in mice.
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