Investigation of the pharmacological effect of cannabidiol on epilepsy, postictal analgesia and acute inflammatory pain

• Grant number: 16/18145-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2016
• End date: October 31, 2017
• Field of knowledge: Biological Sciences - Pharmacology - Neuropsychopharmacology
• Principal Investigator: Norberto Cysne Coimbra
• Grantee: Anderson Justino de Oliveira
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Studies demonstrate that acute tonic-clonic seizures cause an increase in the nociceptive threshold in rodents. It is important to highlight that the post-ictal analgesia was verified through the use of the tail flick test, that causes phasic pain, characterized by finishing as soon as the nociceptive stimulus is ended. In this sense, it is important to verify if this type of analgesia is also verified in rodents with acute inflammatory pain, characterized by being of long term, since it involves a tissue injury. Since cannabidiol (CBD), a component from Cannabis Sativa, has been highlighted as a promising drug for the treatment of epilepsy and, possibly of pain, one of the aims of this study is to verify its action in Pentylenotetrazol (PTZ-induced seizures) treated mice with acute inflammatory pain (caused by formalin injection). It is intended to verify if when cannabidiol inhibit seizures, the post-ictal analgesia will also be reverted. It is important to highlight that firstly, a study will be performed to investigate which dose of PTZ (40 or 80 mg/kg) induce tonic-clonic seizures in mice. The second experimental step consist in tests whereas mice will be injected with 25 ¼l of 2.5 % formalin into the dorsal right hind paw. For 5 min the time spent (in seconds) on licking or lifting this paw will be recorded. Five min after the formalin administration, the animals will receive i.p. injection of vehicle or cannabidiol (15, 30 or 60 mg/kg). After 30 min, they will be injected with pentylenotetrazol (0, 40 or 80 mg/kg) i.p. Approximately after 10 min or when the seizures have ended, the time spent on licking the formalin injected paw will be recorded for 40 min. (AU)