Effects of lemon balm (Melissa officinalis) on behavioral deficits and memory impairment of rats surviving sepsis

Sepsis has become one of the most frequent causes of mortality in intensive care centres. So far, there is no effective pharmacotherapy that can prevent or improve the neurological consequences and enhance survival. The goal of this study is to investigate the neuroprotective effect of lemon balm (Melissa officinalis) on behavioural dysfunctions produced in sepsis-surviving rats. Adult male rats were subjected to caecal ligation and puncture and the control animals were submitted to the sham operation. Lemon balm ethanolic extract or saline, given orally, was administered for one week after surgery procedures. Locomotion, anxiety, depressive behaviour and memory were investigated. In the elevated plus-maze (EPM), the percentage of open arm entries and open arm time was very significant in the animals treated with lemon balm extract, similar to the diazepam response in sham-operated and sepsis-surviving rats. Locomotion in open field tests and the enclosed arm entries in the EPM were not significantly altered by treatments. In the forced swimming (FS) test, the extract was effective at reducing the immobility time as that demonstrated by fluoxetine. In the step-down inhibitory avoidance test, the extract eased the effects on memory of sepsis-surviving animals. Collectively, these results demonstrate that lemon balm ethanolic extract could be used for the prevention of cognitive and moodrelated deficits that may be associated with sepsis sequelae.