Protective effect of Tetrapleura tetraptera (Schum. & Thonn.) fruit extract against haloperidol-induced catalepsy and scopolamine-induced memory impairment: Involvement of antioxidant system

Abstract

Tetrapleura tetraptera fruit infusion is taken as a recuperative tonic and memory enhancer in the traditional African medicine. This study investigates the  neuroprotective and memory enhancing effects of T. tetraptera. The ethanolic fruit extract of Tetrapleura tetraptera (HeTA) (25-100 mg/kg, p.o) was administered for 3 consecutive days, scopolamine (3 mg/kg, i.p.) or haloperidol (1 mg/kg, i.p.) given 1 h post-treatment on day 3. The bar test, elevated plus maze test (EPM) and Morris water maze paradigm (MWM) were used to evaluate the effect of the extract on cataleptic behaviour and memory function, respectively. Biochemical markers of oxidative and nitrosative stress were estimated in rats’ brains after the completion of the MWM task. Haloperidol injection induced time course cataleptic behaviour which was reversed by HeTA (25-100 mg/ kg) treatment in bar test. Scopolamine injection impaired memory function in the EPM and MWM tasks. However, HeTA (25-100 mg/kg) administration significantly (P<0.001) reduced the transfer latency in the EPM as well as session dependent decrease (P<0.001) in escape latency in MWM. Also, HeTA and tacrine improved spatial learning evidenced in the increase (P<0.01) time spent in the target quadrant in the MWM. Moreover, scopolamine increased (P<0.05-0.001) the levels of lipid peroxidation and nitrite generation with concomitant decrease (P<0.05-0.001) in antioxidant enzymes activities in the prefrontal cortex, striatum and hippocampus which were ameliorated with the pretreatment of rats with HeTA or tacrine. Findings from this study indicate anticataleptic and memory enhancing effects of T. tetraptera fruit extract through enhancement of antioxidant defense systems.

Keywords: Dementia; elevated plus maze; Morris water maze; scopolamine; malondialdehyde; 1,1-Diphenyl- 2-picrylhydrazyl (DPPH)