Diazoxide and dimethyl sulphoxide prevent cerebral hypoperfusion-related learning dysfunction and brain damage after carotid artery occlusion

Chronic cerebral hypoperfusion, a mild ischemic condition is associated with advancing age and severity of dementia; however, no unanimous therapy has been established to alleviate related neurological symptoms. We imposed a permanent, bilateral occlusion of the common carotid arteries of rats (n=18) to create cerebral hypoperfusion. A mitochondrial ATP-sensitive K⁺ channel opener diazoxide (DZ, 5 mg/kg) or its solvent dimethyl sulphoxide (DMSO) were administered i.p. (0.25 ml) on five consecutive days after surgery. Sham-operated animals (n=18) served as control for the surgery, while nontreated rats were used as control for the treatments. Three months after the onset of cerebral hypoperfusion, the rats were tested in a hippocampus-related learning paradigm, the Morris water maze. Subsequently, the animals were sacrificed and neurons, astrocytes and microglia were labeled with immunocytochemistry in the dorsal hippocampus. DMSO and diazoxide dissolved in DMSO restored cerebral hypoperfusion-related learning dysfunction and prevented cyclooxygenase-2-positive neuron loss in the dentate gyrus. Cerebral hypoperfusion led to reduced astrocyte proliferation, which was not clearly affected by the treatment. Microglia activation was considerably enhanced by cerebral hypoperfusion, which was completely prevented by diazoxide dissolved in DMSO, but not by DMSO alone. We conclude that diazoxide can moderate ischemia-related neuroinflammation by suppressing microglial activation. Furthermore, we suggest that DMSO is a neuroprotective chemical in ischemic conditions, and it must be considerately used as a solvent for water-insoluble compounds in experimental animal models.