Pain Threshold In Hot Plate Test Research Articles

Evaluation on Analgesic and Anti-Inflammatory Activities of Total Flavonoids from Juniperus sabina.

The leaves of Juniperus sabina (Cupressaceae) are used in traditional Uygur medicine for the treatment of rheumatism and arthritic pain. This study aimed to investigate the analgesic and anti-inflammatory effects of total flavonoids from leaves of Juniperus sabina (JSTF) on rodents. The anti-inflammatory activity was investigated using the carrageenan, egg albumin, or histamine-induced rat paw edema as well as xylene-induced ear edema, capillary permeability, and cotton pellet granuloma while the antinociceptive activity was evaluated using the mouse writhing, formalin, and hot-plate tests. JSTF (125, 250, 500 mg/kg) significantly inhibited xylene-induced ear edema in mice (inhibition ratio as 16.22%, 40.67%, and 51.78%, respectively) and also significantly ameliorated acetic acid increased vascular permeability in mice (inhibition ratio as 11.63%, 32.56%, and 53.49%, respectively). JSTF (250 and 500 mg/kg) gave significant reduction of carrageenin-induced paw oedema at the interval of 1 h and 5 h. Administration of JSTF (500 mg/kg) caused a significant anti-inflammatory effect against oedema induced by egg albumin or histamine at the interval of 0.5 h and 4 h, and both which induced the paw oedema were also inhibited by JSTF (250 mg/kg) at a point in 1, 2, or 3 h after the inflammation. Furthermore, JSTF (125, 250, and 500 mg/kg) produced time-course increase in pain threshold in hot-plate test also. JSTF produced concentration-dependent inhibition on cyclooxygenase-2 (COX-2) or 5-lipoxygenase (5-LO) activities in vitro, and their IC50 values were 31.92 and 129.26 μg/mL, respectively. Moreover, JSTF significantly caused a significant dose-dependent inhibition on acetic acid induced writhing response in mice (inhibition ratio as 23.27%, 36.91%, and 50.76%, respectively). JSTF also significantly ameliorated formalin-induced pain in mice in the late phase on dose-dependent way. These results confirms the clinical use of J. sabina for treatment of rheumatoid arthritis in ethnomedicine, and its effective mechanism will be further studied in the future.

5-HT1A Receptors Mediate Analgesia Induced by Emulsified Sevoflurane in Thermal Nociception but Have Little Effect on Chemical Nociception

Objective: The study aimed to investigate the relationship between the analgesic effect of sevoflurane and 5-serotonin receptor 1A (5-HT_1A R) in the spinal cords of mice. Methods: Analgesic mouse models were established by intraperitoneal injection of emulsified sevoflurane, and the influence of p-MPPF (a specific antagonist of 5-HT_1A Rs) intrathecal injection on the changes in tail-flick latency in tail-withdrawal test, pain threshold in hot-plate test (HPPT), and writhing times in acetic acid-induced writhing test were recorded. Results: Intraperitoneal injection of emulsified sevoflurane alone produced an analgesic effect (p < 0.05). p-MPPF (2, 4, and 8 μg) alone had no impact on tail-flick latency, HPPT, and writhing times in mice (p > 0.05). The 3 doses of p-MPPF reduced the tail-flick latency or HPPT. p-MPPF 8 μg can increase the writhing times (p < 0.05) in analgesic mice with sevoflurane, while p-MPPF 2 and 4 μg did not affect the writhing times. Conclusion: 5-HT_1A Rs in the spinal cord may be an important target for the analgesic effect of sevoflurane on the thermal nociception, but it has little relation to the anti-chemical chemical nociceptive effect of sevoflurane.

The effects of intrathecal injecting capsaicin on the analgesia effects of enflurane and sevoflurane

Objective The present research was designed to explore the role of transient receptor potential vanilloid 1(TRPV1) in analgesia induced by enflurane(Enf) and sevoflurane(Sev). Methods Two hundred and forty mice were completely randomly divided into intraperitoneally (ip) (hot-plate test) or subcutaneously (SC) (acetic acid-induced writhing test) saline and Enf, Sev groups and each group according to intrathecal injection solvent and capsaicin (2.5, 5, 10 ng) was divided into four subgroups. After established the mice model of analgesia by intraperitoneal or subcutaneous injection of appropriate doses of Enf or Sev, we injected different doses of capsaicin intrathecally and observed effects on the pain threshold using the hot-plate and acetic acid-induced writhing test. Results The results showed that intrathecal injection of capsaicin(2.5, 5, 10 ng) did not affect the pain threshold in hot-plate test(HPPT) or the writhing numbers in conscious mice(P>0.05). In contrast, capsaicin (2.5, 5, 10 ng intrathecally) was signiflcantly decreased the HPPT and increased the writhing nubmers [Enf group: (22±7), (24±5), (29±6) vs (16±6), Sev group: (21±6), (23±7), (28±4) vs (13±5)]in mice treated with Enf or Sev(P<0.05). Conclusions These results suggest that spinal TRPV1 may mediate the analgesic effects of Enf and Sev. Key words: Enflurane; Sevoflurane; Analgesia; Intrathecal injection; Transient receptor potential vanilloid 1

Mechanisms of analgesic and anti-inflammatory properties of Annona muricata Linn. (Annonaceae) fruit extract in rodents.

Unripe fruit of Annona muricata Linn. (Annonaceae) (soursop) is used in traditional African medicine for the treatment of neuralgia, rheumatism, and arthritic pain. This study sought to investigate the analgesic and anti-inflammatory effects of lyophilized fruit extract of Annona muricata (AM) in rodents. The analgesic activity was evaluated using the mouse writhing, formalin, and hot-plate tests while the anti-inflammatory action was investigated using the carrageenan-induced rat paw edema and xylene-induced ear edema tests. Pretreatment with AM (50, 100, and 200 mg/kg, p.o.) produced dose-dependent (P<.001) inhibition of writhes and formalin-induced pain in the late phase. AM and morphine produced time-course increase in pain threshold in hot-plate test. However, the analgesic effect elicited by AM was reversed (P<.05) by naloxone pretreatment. Similarly, the time-dependent increase in paw circumference induced by carrageenan was inhibited by AM treatment with peak effect (0.23±0.10 cm; P<.001, 200 mg/kg; 6 h), which was comparatively similar to that of diclofenac treated. Further, the xylene-induced ear edema was significantly reduced by AM (50 or 100 mg/kg) pretreatment; however, the anti-inflammatory effect elicited by AM was prevented by pretreatment of mice with N(G)-nitro-l-arginine (20 mg/kg, i.p., nitric-oxide synthase inhibitor) 15 min before AM (200 mg/kg, p.o.). The in vitro cyclooxygenase assay also showed that AM produced concentration-dependent inhibition of both cyclooxygenase (COX)-1 and COX-2 activity by 39.44%±0.05% and 55.71%±0.12%, respectively, at 100 μg/mL. In conclusion, A. muricata possesses analgesic effect through interaction with opioidergic pathway and anti-inflammatory property through inhibition of chemical mediators of inflammation.

Nicotinic acetylcholine receptors mediate the hypnotic and analgesic effects of emulsified inhalation anesthetics

This study was designed to investigate the role of nicotinic acetylcholine receptors (nAChRs) in hypnosis and analgesia induced by emulsified inhalation anesthetics. After having established the mice model of hypnosis and analgesia by intraperitoneal injections of appropriate doses of enflurane, isoflurane or sevoflurane, we intracerebroventricularly or intrathecally injected different doses of nicotine and then observed the effects on the sleeping time using awaken test and the pain threshold in hot-plate test (HPPT) using hot-plate test. In the awaken test, 10, 20 and 40 microg of nicotine (intracerebroventricularly) significantly decreased the sleeping time of the mice treated with the three emulsified inhalation anesthetics mentioned above (P < 0.05 or 0.01). In the HPPT, 5, 10 and 15 microg of nicotine (intrathecally) did not affect the HPPT in conscious mice (P > 0.05); in contrast, 5, 10 and 15 microg of nicotine (intrathecally) significantly decreased the HPPT of the mice treated with emulsified inhalation anesthetics (P < 0.05 or 0.01). The data presented in this study suggest that nAChRs may be important targets for the hypnotic and analgesic effects induced by emulsified enflurane, isoflurane and sevoflurane.