Mu and Delta Opioid Receptors Oppositely Regulate Motor Impulsivity in the Signaled Nose Poke Task Olmstead, Mary C. ; Ouagazzal, Abdel-Mouttalib ; Kieffer, Brigitte L. Abstract Publication: PLoS ONE Pub Date: February 2009 DOI: 10.1371/journal.pone.0004410 Bibcode: 2009PLoSO...4.4410O