Modified ‘Joyce model’ of opioid dependence/withdrawal

By comprehensive and detailed measurement of the time course of withdrawal signs in rats, Joyce et al. (J. Theo. Biol. 240:531–537, 2006) recently provided a creative quantitative model of the onset of drug dependence based on the requirement of protein synthesis. Because the initial model fit the data imperfectly over the full time course, those authors postulated that additional features would be needed. We report excellent fit of the data (R2 = 0.96) by adding: (1) a transient early phase, and (2) a delay in the buildup of protein.