Figure 8.2:The Ethanolic Extract of Psychotria carrascoana Leaves Inhibits the Acetic Acid-induced Abdominal Constrictions in Mice.

Animals were treated i.p. with EEPc at 10 (n=6); 30 (n=10); or 100 (n=6) mg/kg or vehicle (n=12), 30 min before i.p. injection of 0.8 per cent acetic acid. Ten minutes later, the number of constrictions was registered for 20 min. Values are reported as means±SEM. ^*p<0.05 compared to vehicle.

Discussion and Conclusions

Species from the Psychotria genus have being popularly used for pain treatment (Elisabetsky et al., 1995). Various investigations have being demonstrating a relashionship between the plant analgesic effect and presence of alkaloids with opioide-like activity. In vivo, Elisabetsky and collaborators (1995) described that alkaloids presented in leaves and flowers of Psychotria colorata have marked opiate-like analgesic effects; In vitro, Amador and collaborators (1996) showed an inhibitory effect of P. colorata flower alkaloids on [³H]naloxone binding in rat striata, as well a decrease in adenylate cyclase basal activity.

Pharmacological studies conducted using isolated Psychotria alkaloids have shown mixed mechanisms for its analgesic action: Hodgkinsine, a trimeric pyrrolidinoindoline type alkaloid present as a major constituent of Psychotria spp, has shown to produce dose-dependent, naloxone reversible, analgesic effect in thermal models of nociception and in the capsain-induced pain. In addition, in vivo assays have demonstrated that calycosidine has the same analgesic profile of hodgkinsine (Verotta et al., 2002). On the other hand, psycotridine presented a dose-dependent analgesic effect in the tail flick model of nociception that was not reversed prior treatment with naloxone. Additionally, this substance decreased capsain-induced pain and inhibited binding to cortex membranes. These results ruled out the psycotridine opioid activity and strongly suggested participation of NMDA receptors (Amador et al., 2001).

In the present study we demonstrated the analgesic effect of P. carrascoana in mice. Intraperitoneal treatment with its ethanol extract (EEPc) in mice caused a dose-dependent antinociceptive effect in the three classical experimental models of nociception (acetic acid-induced abdominal-constrictions, 1^st and 2^snd phase of formalin test and hot plate test) tested. This data demonstrated that the ethanol extract of P. carrascoana has central and peripherally mediated antinociceptive activities. In the hot plate test the Psychotria antinociceptive effect was reversed by prior treatment of animals with naloxane, suggesting an opioid activity. The peripheral action may be due to its antiinflammatory activity, but this has to be tested properly in specific inflammatory models.

Figure 8.3:The Ethanolic Extract of Psychotria carrascoana Leaves Inhibits the Neurogenic (a) and the Inflammatory Phase (b), of the Formalin Test.

Animals were treated with EEPc at 10 (n=10), 30 (n=9) or 100 (n=10) mg/kg; i.p. or vehicle (n=12), 30 min before intraplantar injection of 2.5 per cent formaldehyde. The licking time was registered from 0 to 5 min (phase 1, neurogenic) and from 15 to 30 min after formalin (phase 2, inflammatory). Control animals were injected with similar volume of vehicle. Morphine (5mg/Kg; s.c) 30 minutes before formalin challenge was used as positive control. Values are reported as means±SEM. ^*p<0.05 compared to vehicle.

Stay updated, free articles. Join our Telegram channel

Join