ABSTRACT
Cannabis sativa is a member of the family Cannabinaceae. Delta-9-tetrahydrocannabinol is thought to be the principal psychoactive ingredient present in Cannabis and may have important implications for various neurobehavioral processes, including learning, memory, motivation, motor control, etc. Cannabis use is associated with negative health outcomes, psychosocial and cognitive impairments and societal acceptance of cannabis use for medicinal applications continues to increase. Hence, the concerns for this present study. The objectives of the study were to establish the effect of Cannabis sativa on learning and spatial memory; to investigate some neurochemical changes; and to investigate the effects of Cannabis sativa on oxidative stress markers in the brain associated with Cannabis sativa administration. The study used 75 mice, grouped in to three, of 25 mice each. Three standard neurobehavioural test models (EPM, MWM and YM) each for a group were used to assess learning and spatial short term memory. Each of the three groups was further subdivided in to five (5) groups, containing five (5) mice each. Group one and five, the negative and positive control were respectively administered with normal saline and piracetam 100mg/kg, while groups two, three and four were administered with 25mg/kg, 50mg/kg and 75mg/kg of Cannabis sativa extract respectively. All regimens were orally, twice daily and lasted for 21 days. Brain homogenates were used to evaluate acetylcholinesterase, (AchE) activity, dopamine concentration, brain sialic acid concentration, malondialdehyde, (MDA) concentration, Superoxide dismutase, (SOD), and catalase, (CAT). The data obtained from these studies were analysed with statistical package for social science (SPSS) software, version 20 (IBM, USA), using one-way analysis of variance (ANOVA) and Tukey's multiple comparison post hoc test. All data were expressed as mean  SEM and p ≤ 0.05 were considered statistically significant. The viii results of the research showed impairment in learning and spatial short term memory with groups 3 and 4 in the EPM model and MWM model. There was increased concentration of AchE in the cannabis treated groups of the EPM model and groups 3 and 4 of MWM model, but, no significant changes in concentration of AchE in the Y maze model. Dopamine and Total brain sialic acid concentrations decrease in group 4 of all the models. Also, there was increase MDA concentration and decrease in catalase and SOD activities, suggesting oxidative stress. Thus, cannabis sativa in high doses is associated with learning and spatial short term memory impairment via some of the neurochemicals involved in learning and memory.
