Enriched rehabilitation promotes motor recovery in rats exposed to neonatal hypoxia-ischemia

Abstract

Despite continuous improvement in neonatology there is no clinically effective treatment for perinatal hypoxia ischemia (HI). Therefore, development of a new therapeutic intervention to minimize the resulting neurological consequences is urgently needed. The immature brain is highly responsive to environmental stimuli, such as environmental enrichment but a more effective paradigm is enriched rehabilitation (ER), which combines environmental enrichment with daily reach training. Another neurorestorative strategy to promote tissue repair and functional recovery is cyclosporine A (CsA). However, potential benefits of CsA after neonatal HI have yet to be investigated. The aim of this study was to investigate the effects of a combinational therapy of CsA and ER in attempts to promote cognitive and motor recovery in a rat model of perinatal hypoxic-ischemic injury. Seven-day old rats were submitted to the HI procedure and divided into 4 groups: CsA+Rehabilitation; CsA+NoRehabilitation; Vehicle+Rehabilitation; Vehicle+NoRehabilitation. Behavioural parameters were evaluated pre (experiment 1) and post 4 weeks of combinational therapy (experiment 2). Results of experiment 1 demonstrated reduced open field activity of HI animals and increased foot faults relative to shams in the ladder rung walking test. In experiment 2, we showed that ER facilitated acquisition of a staircase skilled-reaching task, increased number of zone crosses in open-field exploration and enhanced coordinated limb use during locomotion on the ladder rung task. There were no evident deficits in novel object recognition testing. Delayed administration of CsA, had no effect on functional recovery after neonatal HI. There was a significant reduction of cortical and hemispherical volume and hippocampal area, ipsilateral to arterial occlusion in HI animals; combinational therapy had no effect on these morphological measurements. In conclusion, the present study demonstrated that ER, but not CsA was the main contributor to enhanced recovery of motor ability after neonatal HI.