Effects of Bromelain on Noradrenaline Release During Anxiety-Like Behaviour Following Intra-Medial Forebrain Bundle 6-OHDA Injection in Rat Model of Parkinsonism

Introduction: Parkinson’s disease (PD) is characterized by emotional dysfunction which is a typical manifestation of non-motor symptoms. Non-motor symptoms may occur simultaneously with motor impairment in PD. Anxiety is a comorbidity in PD. This study therefore addresses the question of whether prior/post 6-OHDA lesion treatment with bromelain can show an effect on the behavioural signs of parkinsonism and damage to the CNS noradrenergic system in experimental rats. Methods: Open field and despair swim tests were used to assess certain psychomotor functions and emotional reactivity in the neurotoxin injected rats. The level of noradrenaline in certain regions of the brain as well as in the blood was further analyzed by enzyme linked immunosorbent assay. Findings: The results showed that unilateral injection of the neurotoxin into the rats’ medial forebrain bundle caused a decrease in the rearing time and a corresponding increase in the time spent grooming. There was a further indication that 6-OHDA injection resulted in the reduction of noradrenaline in the systemic environment. Also, the duration of immobility was increased by 6-OHDA injection but not statistically significant. Pretreatment with bromelain caused a change in the grooming behaviour not consistent with noradrenaline level. Conclusion: This finding suggests that bromelain treatment interferes with the regulation of mood and emotion during the early phase of parkinsonism in the 6-OHDA rat model of PD which was accompanied by changes in noradrenaline level.