Assessing functional outcomes following intracerebral hemorrhage in rats

Abstract

Translational neuroprotective and drug development studies need to be gauged against well-characterized functional outcomes, including motor, sensory and cognitive domains. Since intracerebral hemorrhage (ICH) causes dramatic neurological and cognitive deficits in humans, we hypothesized that ICH would result in prolonged motor-sensory and learning/memory deficits in rats. Neurological tests of sensorimotor functions were performed before ICH, 1-3 days and 10 weeks after ICH. Water maze, open field, and rotarod performance was tested 2 and 8 weeks after ICH. Early neurological evaluations revealed significant deficits, with almost full recovery by 10 weeks. The water maze revealed significant learning (but not motor) deficits at 2 weeks, but by 8 weeks, the learning deficits had diminished and significant motor deficits had emerged, coinciding with a drop in activity. The injured hemisphere showed significant atrophy at sacrifice. Therefore, ICH produced detectable cognitive and motor deficits in rats that evolved over a 10-week period, and thereby provides a suitable baseline for analysis of future therapeutic interventions following hemorrhagic stroke.

Fig. 1 –. Declining level of activity with age in spite of steady weight gain.

Both graphs show mean +/− standard error of the mean. (A) No difference between sham and ICH rats was observed at either time-point, however a significant treatment × time point interaction (# p<0.00003) revealed that ICH rats spent less time moving at 8 weeks than they did at 2 weeks. (B) No difference in weight was observed at any time-point measured.

Fig. 2 -. Water maze motor measures deteriorate with age.

(A) Mean +/− 95% confidence intervals. Sham rats had no bias toward turning left versus right whilst swimming, but ICH rats were significantly biased toward turning to the right at both 2 and 8 weeks (* p<0.05). (B) Mean +/− standard error of the mean. ICH rats swam more slowly than sham rats (* p<0.002), and ICH rats swam more slowly at 8 weeks than at 2 weeks (# p<0.006).

Fig. 3 -. Water maze performance improves with age.

All graphs show mean +/− standard error of the mean. (A and B) Cued learning: ICH rats swam further before finding the visible escape platform († p<0.005), but the difference only existed at 2 weeks (* p<0.05). (C and D) Spatial learning: ICH rats swam further before finding the submerged escape platform († p<0.0003), but the difference only existed at 2 weeks (* p<0.05)

Fig. 4 -. Neurological outcomes.

Both graphs show mean +/− standard error of the mean. (A) Forelimb placing and (B) Neurological test battery scores at baseline (pre-ICH), 1, 2, 3 and 70 days after ICH induction. ICH rats performed significantly worse compared to shams over the first three days (* p<0.001) with no significant differences at baseline or 10 weeks later.

Fig. 5 -. Long-term cerebral atrophy and forelimb-use asymmetry outcomes.

Both graphs show mean +/− standard error of the mean. (A): ICH rats had significant brain atrophy compared to shams (* p<0.001). (B): Forelimb use asymmetry at 10 weeks after ICH revealed no differences. (C and D) Representative photos of cresyl violet stained coronal brain sections obtained at 10 weeks after ICH showing that (D) ICH animals had visible atrophy near cerebral ventricles, whereas (C) shams had no discernable cerebral tissue loss. Asterisk (*) indicates site of needle-track.