title: Behavioural and Electrophysiological Evidence of Impaired Learning and Memory in Male Sprague Dawley Rats following Subchronic Exposure to Standardised Methanolic Extract of Mitragyna speciosa Korth.
abstract: BACKGROUND
  Mitragyna speciosa (MS) or ketum is primarily found in Southeast Asia, particularly in northern Malaysia and Thailand. The medicinal value of this plant has attracted significant attention from both herbal medicine practitioners and scientists worldwide. Despite having illegal consumption status, the plant merits study. We conducted a series of experiments to test our hypothesis that ketum impairs both learning and memory in rats.
  
  
  METHODS
  Ketum leaves were extracted using methanol and standardised for the amount of its pure compound, mitragynine. Rats were divided into groups for a passive avoidance task and long-term potentiation (LTP) extracellular recording. In the extracellular recording condition, rats were grouped into control, MS100 (100 mg/kg of ketum extract), MS200 (200 mg/kg of ketum extract), and MS500 (500 mg/kg of ketum extract) groups. An additional group that received morphine was included in the passive avoidance task (10 mg/kg), and there were six animals per group. Rats received daily treatments orally for 28 days for both experiments.
  
  
  RESULTS
  Using a passive avoidance task, our data revealed that the rats' memory significantly increased with increasing doses of MS compared to the morphine-treated group. Our findings from LTP recordings showed that LTP was fully blocked by the higher doses of MS.
  
  
  CONCLUSIONS
  We speculate on the possibility that additional factors were involved in the passive avoidance task because it was an in vivo animal study, while the LTP experiment solely involved brain slices.
authors.affiliation: Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.
authors.forename: Mohd Ulul
authors.initials: MU
authors.lastname: Ilmie
authors.affiliation: Centre for Drug Research, Universiti Sains Malaysia, 11800 Minden, Pulau Pinang, Malaysia.
authors.forename: Sharif Mahsufi
authors.initials: SM
authors.lastname: Mansor
authors.affiliation: Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia; Center for Neuroscience Services and Research, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia; Hospital Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.
authors.forename: Jafri Malin
authors.initials: JM
authors.lastname: Abdullah
keywords: Methanolic extract; Mitrgyna speciosa; Subchronic exposure