VMAT-DAT-Dopamine Regulatory System Involved in the Protective Effect of 3-n-Butylphthalide Against Ischemic Stroke

A stable uptake-release cycle system of dopamine is dependent upon two transporters, dopamine transporter (DAT) and vesicular monoamine transporter (VMAT). Whether the regulation system of dopamine is involved in the neuroprotection mediated by 3-n-butylphthalide (NBP) against ischemic stroke injury is unclear.

Middle cerebral artery occlusion (MCAO) was subjected to evaluate the protection of NBP. In vivo microdialysis measurements of neurotransmitters were recorded in the ischemic penumbral area. Brain slices were prepared in MCAO mice to record synaptic function, including miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs).

NBP decreased the infarct size with a dose-dependent manner, and significantly reduced the level of glutamate, while markedly increasing dopamine release. The expressions of DAT and VMAT were significantly decreased by MCAO, which were reversely enhanced by NBP. Pretreatment with VMAT inhibitor, reserpine, abolished the dopamine increase and eliminated the neuroprotection of NBP. The balance between excitatory and inhibitory synaptic transmission is disturbed by ischemic injury and reversed by NBP. Reserpine eliminated the effect of NBP against the disturbance of mEPSCs and mIPSCs. Inhibition of dopamine-1 receptor (D₁R) or adenosine A₁ receptors (A₁R: downstream of D₁R) both eliminated the regulation of NBP on the synaptic function and abolished the neuroprotection of NBP.

The neuroprotective effect of NBP against cerebral ischemic injury may involve the upregulation of the VMAT-DAT-dopamine cycle, which appears to contribute to the amelioration of synaptic dysfunction. The activation of D₁R and its downstream adenosine A₁Rs is involved in the neuroprotection mechanism.