1. Babbini M, Davis WM (1972) Time dose relationships for locomotor activity effects of morphine after acute or repeated treatment. Br J Pharmacol 46:213?224
2. Brady LS, Holtzman SG (1981) Effects of intraventricular morphine and enkephalins on locomotor activity in non-dependent, morphine-dependent and post-dependent rats. J Pharmacol Exp Ther 218:613?620
3. Broekkamp CLE, Phillips AG, Cools AT (1979) Stimulant effects of enkephalin microinjection into the dopaminergic A10 area. Nature 278:560?562
4. Browne RG, Segal DS (1978) ?-endorphin and opiate-induced immobility: behavioral caracterization and tolerance development. In: Van Ree JM, Terenius L (eds) Characteristics and functions of opioids. Elsevier/North-Holland Biomedical Press, Amsterdam, pp 413?414
5. Buxbaum DM, Yarborough GG, Carter ME (1973) Biogenic amines and narcotic effects. I-Modification of morphine-induced analgesia and motor activity after activation of cerebral amine levels. J Pharmacol Exp Ther 185:317?327