The antinociceptive effect of artemisinin on the inflammatory pain and role of GABAergic and opioidergic systems / 대한통증학회지

BACKGROUND: Pain is a complex mechanism which involves different systems, including the opioidergic and GABAergic systems. Due to the side effects of chemical analgesic agents, attention toward natural agents have been increased. Artemisinin is an herbal compound with widespread modern and traditional therapeutic indications, which its interaction with the GABAergic system and antinoniceptive effects on neuropathic pain have shown. Therefore, this study was designed to evaluate the antinociceptive effects of artemisinin during inflammatory pain and interaction with the GABAergic and opioidergic systems by using a writhing response test. METHODS: On the whole, 198 adult male albino mice were used in 4 experiments, including 9 groups (n = 6) each with three replicates, by intraperitoneal (i.p.) administration of artemisinin (2.5, 5, and 10 mg/kg), naloxone (2 mg/kg), bicuculline (2 mg/kg), saclofen (2 mg/kg), indomethacin (5 mg/kg), and ethanol (10 mL/kg). Writhing test responses were induced by i.p. injection of 10 mL/kg of 0.6% acetic acid, and the percentage of writhing inhibition was recorded. RESULTS: Results showed significant dose dependent anti-nociceptive effects from artemisinin which, at a 10 mg/kg dose, was statistically similar to indomethacin. Neither saclofen nor naloxone had antinociceptive effects and did not antagonize antinociceptive effects of artemisinin, whereas bicuculline significantly inhibited the antinocicptive effect of artemisinin. CONCLUSIONS: It seems that antinocicptive effects of artemisinin are mediated by GABAA receptors.

The effect of melanocortin (Mc3 and Mc4) antagonists on serotonin-induced food and water intake of broiler cockerels

The current study was designed to examine the effects of intracerebroventricular injections of SHU9119 [a nonselective melanocortin receptor (McR) antagonist] and MCL0020 (a selective McR antagonist) on the serotonin-induced eating and drinking responses of broiler cockerels deprived of food for 24 h (FD24). For Experiment 1, the chickens were intracerebroventricularly injected with 2.5, 5, and 10 microg serotonin. In Experiment 2, the chickens received 2 nmol SHU9119 before being injected with 10 microg serotonin. For Experiment 3, the chickens were given 10 microg serotonin after receiving 2 nmol MCL0020, and the level of food and water intake was determined 3 h post-injection. Results of this study showed that serotonin decreased food intake but increased water intake among the FD24 broiler cockerels and that these effects occurred in a dose-dependent manner. The inhibitory effect of serotonin on food intake was significantly attenuated by pretreatment with SHU9119 and MCL0020. However, the stimulatory effect of serotonin on water intake was not altered by this pretreatment. These results suggest that serotonin hypophagia and hyperdipsia were mediated by different mechanisms in the central nervous system, and that serotonin required downstream activation of McRs to promote hypophagia but not hyperdipsia in the FD24 chickens.

Effects of central histamine receptors blockade on GABA(A) agonist-induced food intake in broiler cockerels.

In this study, the effect of intracerebroventricular (i.c.v) injection of H1, H2 and H3 antagonists on feed intake induced by GABA(A) agonist was evaluated. In Experiment 1, the animals received chloropheniramine, a H1 antagonist and then muscimol, a GABA(A) agonist. In Experiment 2, chickens received famotidine, a H2 receptor antagonist, prior to injection of muscimol. Finally in Experiment 3, the birds were injected with thioperamide, a H3 receptor antagonist and muscimol. Cumulative food intake was measured 15, 30, 45, 60, 90, 120, 150 and 180 min after injections. The results of this study indicated that effects of muscimol on food intake inhibited by pretreatment with chloropheneramine maleate (p < or = 0.05), significantly, while the famotidine and thioperamide were ineffective. These results suggest the existence of H1-receptor mediated histamine-GABA(A) receptor interaction on food intake in broiler cockerels.