Late Atomoxetine or Fluoxetine Treatment with Low Duration Voluntary Running Facilitate Recovery of the Motor Function after Photothrombotic Stroke in Mice

Abstract

Many stroke survivors suffer long‐term functional disabilities with no effective treatment option available. For that reason, we tested the potential effects of enhancing noradrenergic and serotoninergic systems in combination with delayed voluntary running on recovery after stroke in mice. To accomplish this, we used adult male mice (n=12/group) and divided them into sham, stroke, vehicle, or drug‐treated groups with either selective norepinephrine reuptake inhibitor atomoxetine (0.3, 1 mg/kg, once a day i.p.) or selective serotonin reuptake inhibitor fluoxetine (3, 10 mg/kg, once a day i.p.) starting from day 5 after stroke and continued for 12 days. For evaluation of motor function, we used grid walking and cylinder tests 3 days prior and 3, 7, 14, 28, 42 days after using ischemic stroke model (photothrombosis). At 42 days after stroke, mice brains were collected either after fixing the brain through cardiac perfusion (for infarct size measurements and immunohistochemistry experiments after brain sectioning) or as a fresh tissue from the motor cortex area (for immunoblotting experiments).The results of both motor function tests showed that all stroke‐subjected groups had comparable and substantial motor impairment on day 3 after stroke when compared to their baseline and that voluntary running group did not significantly improve throughout the days after stroke. However, administrating either atomoxetine or fluoxetine along with exercise promoted motor recovery at 42 days after stroke dose‐dependently with no significant changes seen in infarct size among groups (0.5 ± 0.1 mm3). Further, immunoblotting experiment showed no significant changes amongst groups in synaptophysin, an integral membrane glycoprotein of neuronal synaptic vesicles, nor with PSD‐95, an excitatory postsynaptic density scaffolding protein, after normalization to beta actin in the ischemic hemisphere. However, the immunohistochemistry data showed that atomoxetine and fluoxetine treatment significantly decreased the expression of parvalbumin (PV), a calcium binding albumin protein associated with depressing synapses, in the boundaries of medial agranular cortex and medial frontal cortex areas of the ischemic hemisphere when compared to their corresponding area in the healthy hemisphere. Whereas no significant relative changes seen with the expression of PV showed between the healthy and ischemic hemispheres of sham, stroke, and vehicle groups. Our data showed that low duration voluntary running does not facilitate motor recovery independently after ischemic stroke in mice. But it promoted recovery of motor function only when combined with atomoxetine or fluoxetine in a dose‐dependent manner. Our data showed a significant decrease of the inhibitory interneurons PV concomitant with the recovery seen with atomoxetine and fluoxetine treatment. Our ongoing experiments include the evaluation of growth associated protein (GAP‐43) and glutamate receptors expression.Support or Funding InformationResearch in the Karamyan laboratory is supported by R01NS106879Enhanced motor recovery of mice treated with atomoxetine or fluoxetine after an experimental stroke in the grid walking test (A) and the cylinder test (B).Figure 1Atomoxetine and fluoxetine treatment significantly decreased parvalbumin expression in the ischemic hemisphere compared to the healthy hemisphere on 42 days after stroke.Figure 2