Protective effect of minocycline treatment on striatal ischemia

Anxiety after cardiac arrest/cardiopulmonary resuscitation: exacerbated by stress and prevented by minocycline

BACKGROUND AND PURPOSE

Stress is an important risk factor for cardiovascular disease; however, most of the research on this topic has focused on incidence rather than outcome. The goal of this study was to determine the effects of prior exposure to chronic stress on ischemia-induced neuronal death, microglial activation, and anxiety-like behavior.

METHODS

In Experiment 1, mice were exposed to 3 weeks of daily restraint (3 hours) and then subjected to either 8 minutes of cardiac arrest/cardiopulmonary resuscitation (CA/CPR) or sham surgery. Anxiety-like behavior, microglial activation, and neuronal damage were assessed on postischemic Day 4. In Experiment 2, mice were infused intracerebroventricularly with minocycline (10 microg/day) to determine the effect of inhibiting post-CA/CPR microglial activation on the development of anxiety-like behavior and neuronal death.

RESULTS

CA/CPR precipitated anxiety-like behavior and increased microglial activation and neuronal damage within the hippocampus relative to sham surgery. Prior exposure to stress exacerbated these measures among CA/CPR mice, but had no significant effect on sham-operated mice. Treatment with minocycline reduced both neuronal damage and anxiety-like behavior among CA/CPR animals. Anxiety-like behavior was significantly correlated with measures of microglial activation but not neuronal damage.

CONCLUSIONS

A history of stress exposure increases the pathophysiological response to ischemia and anxiety-like behavior, whereas inhibiting microglial activation reduces neuronal damage and mitigates the development of anxiety-like behavior after CA/CPR. Thus, modulating inflammatory signaling after cerebral ischemia may be beneficial in protecting the brain and preventing the development of affective disorders.

Delayed combinatorial treatment with flavopiridol and minocycline provides longer term protection for neuronal soma but not dendrites following global ischemia

We previously reported that delayed administration of the general cyclin-dependent kinase inhibitor flavopiridol following global ischemia provided transient neuroprotection and improved behavioral performance. However, it failed to provide longer term protection. In the present study, we investigate the ability of delayed flavopiridol in combination with delayed minocycline, another neuroprotectant to provide sustained protection following global ischemia. We report that a delayed combinatorial treatment of flavopiridol and minocycline provides synergistic protection both 2 and 10 weeks following ischemia. However, protected neurons in the hippocampal CA1 are synaptically impaired as assessed by electrophysio logical field potential recordings. This is likely because of the presence of degenerated processes in the CA1 even with combinatorial therapy. This indicates that while we have addressed one important pre-clinical parameter by dramatically improving long-term neuronal survival with delayed combinatorial therapy, the issue of synaptic preservation of protected neurons still exists. These results also highlight the important observation that protection does not always lead to proper function.