Post-traumatic brain injury antithrombin III recovers Morris water maze cognitive performance, improving cued and spatial learning

Abstract

Background: Neuroinflammation and cerebral edema development following severe traumatic brain injury (TBI) affect subsequent cognitive recovery. Independent of its anticoagulant effects, antithrombin III (AT-III) has been shown to block neurovascular inflammation after severe TBI, reduce cerebral endothelial-leukocyte interactions, and decrease blood-brain barrier permeability. We hypothesized that AT-III administration after TBI would improve post-TBI cognitive recovery, specifically enhancing learning, and memory.

Methods: Fifteen CD1 male mice were randomized to undergo severe TBI (controlled cortical impact [CCI]: velocity, 6 m/s; depth, 1 mm; diameter, 3 mm) or sham craniotomy and received either intravenous AT-III (250 IU/kg) or vehicle (VEH/saline) 15 minutes and 24 hours post-TBI. Animals underwent Morris water maze testing from 6 to 14 days postinjury consisting of cued learning trials (platform visible), spatial learning trials (platform invisible, spatial cues present), and probe (memory) trials (platform removed, spatial cues present). Intergroup differences were assessed by the Kruskal-Wallis test (p < 0.05).

Results: Morris water maze testing demonstrated that cumulative cued learning (overall mean time in seconds to reach the platform on days 6-8) was worst in CCI-VEH animals (26.1 ± 2.4 seconds) compared with CCI-AT-III counterparts (20.3 ± 2.1 seconds, p < 0.01). Cumulative noncued spatial learning was also worst in the CCI-VEH group (23.4 ± 1.8 seconds) but improved with AT-III (17.6 ± 1.5 seconds, p < 0.01). In probe trials, AT-III failed to significantly improve memory ability. Animals that underwent sham craniotomy demonstrated preserved learning and memory compared with all CCI counterparts (p < 0.05).

Conclusion: Antithrombin III improves neurocognitive recovery weeks after TBI. This improvement is particularly related to improvement in learning but not memory function. Pharmacologic support of enhanced learning may support new skill acquisition or relearning to improve outcomes after TBI.

Level of evidence: Therapeutic/care management, level II.

Figure 1.

Timeline of experimental procedures. CCI: Controlled Cortical Impact, ATIII: Antithrombin III, NS: Normal Saline.

Figure 2.

Cued Learning Trials (A) Daily assessment of the mean time needed for each group to reach the visible cued platform. Both SHAM and CCI+ATIII groups improved with time and took less time to reach the platform learning faster than the CCI+VEH group which was slower to improve and cut down their mean time needed to reach the platform. The difference was particularly manifest on the 7th day after injury (p<0.05). (B) Cumulative cued learning (mean group times across all daily cued learning trials) was greatest in the CCI+VEH group, significantly worse than in CCI+ATIII and SHAM counterparts (p<0.01).

Figure 3.

Spatial Learning Trials. (A) Of all groups, CCI + VEH animals showed the slowest improvement of reducing the time to reach the platform. The difference was most significant on the 13th after injury (p<0.05 vs CCI+ATIII and p<0.01 vs SHAM). (B) Cumulative spatial learning. The CCI+VEH group’s performance was significantly worse than with AT-III treatment which resulted in times comparable to uninjured SHAM counterparts.

Figure 4.

Probe Memory Trials. There were no significant differences in any of the parameters measured among the 2 injured groups. Uninjured animals consistenly fared better and demonstrated faster times to reach the platforms prior location.