Lipopolysaccharide treatment in the subacute stage of cervical spinal cord injury enhances motor recovery and increases anxiety-like behaviour in female rats

STUDY PURPOSE: Previous published work in our laboratory found that eliciting inflammation with lipopolysaccharide (LPS) in the chronic (8 weeks) stage of cervical level 4 dorsolateral quadrant spinal cord injury (SCI) enhances the efficacy of rehabilitative training (10.1093/brain/awy128). The purpose of the present study is to determine whether sub-acute LPS treatment has a similar effect, since the lesion environment is already in a more inflammatory state at this earlier time point. 2 cohorts of female Lewis rats (n=50) were included for the present data. Of those 50, 22 did not participate (lack of attempts) in rehabilitative training but were still included for their behavioural data in the elevated plus maze. Rats were pre-trained on a single pellet reaching task prior to SCI. 10 days after a unilateral dorsal quadrant cut lesion (Cervical level 4; ipsilateral to preferred paw) rats received a single intraperitoneal injection of either 0.5mg/kg LPS or saline followed by 6 weeks of rehabilitative training. DATA COLLECTED: Data collected include: sickness behaviour, weight, and body temperature measured before, 4, 8, 24, 48, and 72 hours after LPS or saline injections; rat’s success rate and attempt rate in the single pellet reaching task; success rate in the gap test (where a physical gap was introduced to between the pellet dispenser and the rat so they could not scoop the pellet into their mouths); High speed analysis of the rat’s reaching and grasping movements before and after SCI; Horizontal ladder, cylinder, open field and Von Frey tests; lesion analysis and analysis of corticospinal tract sprouting into the grey matter; histological analysis of microglia and astrocytes rostral, caudal and at the injury site; elevated plus maze. DATA USAGE NOTES: The present data shows that a single injection of LPS in the sub-acute stage of SCI has similar beneficial effects on motor recovery as chronic application. Compared to rats that did not receive LPS, LPS treated rats had a higher success rate in the trained single pellet reaching tasks, particularly in the gap test that did not allow for compensatory scooping movements. Lipopolysaccharide treated rats also displayed a chronic (tissue collected 8 weeks following injections) reduction of microglia and astrocyte expression around the lesion site. LPS treated rats also have improved motor recovery in the untrained cylinder test. However, this motor recovery came at a cost since inducing inflammation also had a long-term (i.e. 4 weeks after injections) negative effect on anxiety-like behaviour.