(-)-Quinpirole hydrochloride is an ergoline small molecule selective agonist of D2-like dopamine receptors. The D2-like class includes the D2DR, D3DR and D4DR (D2, D3, and D4 dopamine receptors), and structural similarity of each of these receptor subtypes limits agonist selectivity to the D2-like receptors as a group. Research of conditions of dopamine deficiency such as schizophrenia and Parkinson's disease is usually directed at the D2-like dopamine receptors, and (-)-Quinpirole has been employed along with other D2-like agonists in perturbing and elucidating the chemical landscape beneath these conditions. (-)-Quinpirole demonstrates a neuroprotective effect against glutamate excitotoxicity through D2 receptor agonism, protecting cells from calcium influx, nitric oxide introduction and peroxynitrile generation, all thought to be mediators of glutamate excitotoxicity. The degeneration of dopaminergic neurons by oxygen free radical species is implicated in the progression of Parkinson's disease, and stimulation of D2 receptors by (-)-Quinpirole demonstrated protection against and scavenging of the harmful radicals - this activity was blocked by both a D2 receptor antagonist and a protein synthesis inhibitor, indicating that stimulation of the D2 receptor signals the dopaminergic cell to produce radical-scavenging proteins for protection.
