James Surmeier of Northwestern University's Feinberg School of Medicine in Chicago says the connection between Parkinson's and locus coeruleus neurons makes sense. "Locus coeruleus neurons are very similar electrophysiologically to substantia nigra dopamine-containing neurons," he says, in that they act as a pacemaker, setting the tone for the dopaminergic cells, which in turn modulate neurons in the striatum.

Weinshenker says that to improve the mouse model, he would consider breeding genetically normal mice and then selectively killing dopamine-producing cells with MPTP and norepinephrine-containing neurons with a drug called DSP4. That would likely produce a mouse that is both neurophysiologically and behaviorally similar to a human Parkinson's patient.

He adds that in terms of therapies for Parkinson's patients, "it might be worth treating the norepinephrine as well as the dopamine system," by supplementing the drug L-dopa, the current standard in care, with a tricyclic antidepressant, which is known to improve norepinephrine signaling.

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