The effect of inhaling rosemary compound essential oil on learning and memory in dementia

Abstract

Objective To determine the effect of inhaling rosemary compound essential oil on learning and memory and the expression of choline acetyl transferase (ChAT) in the CA1 region of the hippocampus in rats with vascular dementia (VD).Methods A modified 2-VO method was used to induce permanent brain hypoperfusion,and thus VD,in 60 male SD rats aged 2 months.They were then randomly divided into a normal control group (n =10),a sham-operation group (n =10),a model group (n =10),a rosemary compound essential oil group (n =10) and an edaravone group (n =10).The rosemary compound essential oil group inhaled a compound of the essential oils of rosemary,eugenol and peppermint once a day; the edaravone group was given a daily injection of edaravone injecta.Both the interventions lasted for 65 days.A water maze was used to test their learning and memory abilities.Morphological damage in the CA1 region of the hippocampus and the expression of ChAT were also observed.Results The learning and memory abilities of the model group were significantly weaker compared with the sham-operated group and the normal controls.The rats in the rosemary compound essential oil and edaravone groups were obviously better than those in the model group,but there was no significant difference between rosemary compound essential oil group and the edaravone group.The morphological damage observed in the hippocampus and striatum of the model group was significantly greater,on average,than that observed in the rosemary compound essential oil group and the edaravone group.The average number of ChAT positive units in the CA1 region of the hippocampus was significantly greater in both the rosemary compound essential oil group and the edaravone group compared with the model group,but there was no significant difference between the rosemary compound essential oil group and the edaravone group.Conclusions Inhaling rosemary compound essential oil can improve the learning and memory abilities of rats with VD caused by permanent chronic brain hypoperfusion.It decreases the damage to the neurons of the hippocampus,increases the expression of ChAT,and shows a therapeutic effect on VD,at least in rats. Key words: Dementia, vascular; Memory; Aromatherapy; Rats