EFFECT OF DELTA(9)-TETRAHYDROCANNABINOL ON SHORT-TERM-MEMORY IN THE RAT

We have reported that marihuana and its principal psycoactive compound, Delta(9)-tetrahydrocannabinol (Delta(9)-THC) produce alterations in several cerebral areas after acute treatment. Based on the involvement of 5-hydroxytryptamine (5-HT) on memory and learning and the reported effects of Delta(9)-THC on short-term memory, we designed an experiment to evaluate the memory performance and its possible relationship with serotonergic alterations after Delta(9)-THC administration. Male Wistar rats received an acute oral dose of THC (5 mg/kg). Short-Term memory was tested on a radial 8-arm maze with a 5 s delay, after 35 days of trainning. The animals were food deprived and adjusted for growth. 5-HT and its metabolite, 5-HIAA, levels were measured in cerebral cortex, dorsal hippocampus, ventral hippocampus, rostral neoestriatum and amygdala basal nucleus, by HPLC-ED. The experiment indicates an impairment of short-term memory in the radial maze test after Delta(9)-THC administration. The control group performed the test without errors, while the treated group made a significant number of errors (Z = 0.019, Mann-Whitney test). This behavioral effect did not seem to be related to serotonergic alterations, as the 5-HT turnover rate was not different between treated and control animals.