Delayed minocycline treatment reduces long-term functional deficits and histological injury in a rodent model of focal ischemia

doi:10.1016/j.neuroscience.2006.03.071

Neuroscience

Volume 141, Issue 1, 2006, Pages 27-33

https://doi.org/10.1016/j.neuroscience.2006.03.071 Get rights and content

Abstract

The absence of effective treatments for stroke presents a critical need for novel strategies that can reduce ischemic injury. Neuroinflammation following focal ischemia induces secondary injury in the region surrounding the insult, thus anti-inflammatory agents are potential neuroprotectants. Minocycline is one such agent possessing neuroprotective properties, however many studies examining minocycline after ischemia have used minimal delays between ischemia and treatment, short survival periods, and lack measures of functional outcome. Such studies do not distinguish whether minocycline provides sustained protection or merely delays cell death. This study was designed to address some of these concerns. Male Sprague–Dawley rats were treated with multiple doses of minocycline (45 mg/kg i.p.) or vehicle beginning 2.5 h after endothelin-1-induced focal ischemia. Measures of forelimb asymmetry and skilled reaching (staircase test) were used to determine functional outcome 7, 15 and 28 days after ischemia. Long-term functional assessment indicates that minocycline provides limited benefit in the staircase test, but confers long-term benefit in the forelimb asymmetry test. Subcortical and whole hemisphere infarct volumes were reduced by 41 and 39% respectively in minocycline-treated animals. Further analysis revealed that minocycline attenuated long-term white matter damage adjacent to the striatal injury core, which correlated with sustained functional benefits. This study indicates that delayed minocycline treatment improves long-term functional outcome which is linked to protection of both white and gray matter.

Section snippets

Subjects

Forty-five male Sprague–Dawley rats (Vivarium, Memorial University, St. John’s, NL, Canada) weighing approximately 300 g at the time of surgery were housed in pairs in standard Plexiglas cages maintained on a reverse 12-h light/dark cycle. Food and water were freely available, except when food was restricted during behavioral training and assessment (12–15 g per day). Random assignment to treatment groups was performed prior to surgery. Experimental procedures were approved by the Memorial

Drug treatment and surgery effects

Minocycline is an acidic compound and may cause behavioral side effects in treated animals (e.g. lethargy). To examine adverse drug side effects on animal weight and behavior, sham animals were injected with minocycline (S+M) or vehicle (S+V). There was no significant weight loss due to treatment in S+M animals (t₍₁₃₎=−0.93, P>0.05). Behavior tests showed no differences in S+M and S+V performance (data not shown) so these data were pooled for all analyses (Sham). There was a significant weight

Discussion

The present findings demonstrate robust neuroprotection in minocycline-treated animals one month following focal ischemia. In the cortex there was a trend toward neuroprotection, whereas striatal damage was clearly attenuated by minocycline treatment. Delayed minocycline treatment has been previously shown to reduce cortical and subcortical infarct by 65 and 42% respectively when administered 2 h following middle cerebral artery occlusion (Yrjanheikki et al., 1999), however infarct measures

Conclusions

Delayed treatment with the anti-inflammatory drug minocycline attenuated focal ischemic injury induced by ET-1. In addition there was a reduction in striatal WM injury. Together this translated into improved behavioral outcome. However, the mechanisms of protection provided by minocycline and the conditions under which it is most effective need further elucidation before clinical studies in stroke should be undertaken.

Acknowledgments

The authors thank Sue Evans for technical assistance. Funding for this project was provided by grants from NSERC, the Canadian Stroke Network and the Heart and Stroke Foundations of New Brunswick, and Newfoundland and Labrador awarded to Dale Corbett. Krista Hewlett was the recipient of an NSERC Undergraduate Student Research Award. D.C. holds a Canada Research Chair in Stroke and Neuroplasticity.

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Citation Excerpt :
Additionally, it should be noted that in a preliminary experiment a high number of animals died following ET-1 injection into the NAc alone (Supplemental Fig. 6) as occurred in the current study in combination with ET-1 injection into the mPFC. It is unlikely that these deaths were a result of the long duration of surgery, as the surgery procedure took an equal amount of time among all groups, or the dose of ET-1 chosen, as it has been used in other studies without affecting mortality rates [22,42,43]. However, to our knowledge, this is the first study investigating the effects of ET-1 injections into the NAc so it is possible that restricted blood flow in this region results in secondary damage to other regions.
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Behavioural neuroscienceDelayed minocycline treatment reduces long-term functional deficits and histological injury in a rodent model of focal ischemia

Abstract

Section snippets

Subjects

Drug treatment and surgery effects

Discussion

Conclusions

Acknowledgments

Prog Neurobiol

Exp Neurol

Trends Neurosci

Trends Neurosci

Neuroscience

Neuroscience

Neurobiol Dis

Brain Res

Brain Res

Neuropharmacology

J Neurol Sci

Exp Neurol

Neurobiol Dis

Exp Neurol

J Biol Chem

Brain Res

Exp Neurol

Why are stroke patients excluded from TPA therapy?

Neurology

Inflammatory mediators and strokenew opportunities for novel therapeutics

J Cereb Blood Flow Metab

Microglial-neuronal interactions in synaptic damage and recovery

J Neurosci Res

Behavioural neuroscience
Delayed minocycline treatment reduces long-term functional deficits and histological injury in a rodent model of focal ischemia