RESUMO
Background and purpose: The purpose of the current study was to investigate the protective effects of acute and chronic administration of different doses of vitamin D3 on pentylenetetrazol (PTZ)-induced epileptiform activities in rats. Experimental approach: Sixty Wistar rats in chronic and acute groups were used in this study. In the chronic groups, animals received vitamin D3 at 50, 100, and 150 µg/kg; vitamin D3 (50 µg/kg, i.p.) + diazepam (0.1 mg/kg, i.p.), and almond oil (i.p.) daily for two weeks whereas, in the acute groups the animal received a single dose of chemicals just 30 min before PTZ administration. The electrophysiological recording was performed by implanting a unilateral bipolar electrode in the pyramidal cell layer of the CA1 region of the hippocampus. Epileptic activities were induced by intraperitoneal injection of PTZ (80 mg/kg, i.p.). The spike count and amplitude were analyzed using the eTrace software. Finding/Results: Chronic administration of all doses of vitamin D3 and its combination with diazepam significantly reduced both spike counts and amplitudes following PTZ administration. While the acute doses were ineffective. Conclusion and implication: The results of the study indicated that chronic but not acute administration of vitamin D3 has a protective effect on PTZ-induced epileptiform activity in rats.
RESUMO
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.
RESUMO
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.
