Complex sentence: The effects of endogenous oxytocin concentrations can directly impact on drug effects, but bilateral interactions with numerous systems, including the dopamine system, Hypothalamic--pituitary--adrenal axis and immune system, can impact on development of dependence.
Split into simpler sentences: The effects of endogenous oxytocin concentrations can directly impact on drug effects. Also bilateral interactions with numerous systems, including the dopamine system, Hypothalamic--pituitary--adrenal axis and immune system, can impact on development of dependence.