Abstract: This invention pertains to the discoveries that orexin and/or CRF increase NMDAR (N-methyl-D-aspartate receptor)-mediated currents at excitatory synapses onto a subset of dopamine cells in the ventral tegmental area (VTA) in the mammalian brain. The orexin effect can be blocked by an orexin receptor type 1 (OXR1). The CRF effect can be blocked by a CRF receptor 2 (CRF-R2) antagonist or by an inhibitor of the CRF-binding protein (CRF-BP). Methods are provided that exploit these discoveries to modulate NMDAR-mediated currents in vivo and in vitro and to screen for modulators (upregulators or downregulators) of NMDA-mediated currents. In vivo methods include the use of modulators of the orexin and CRF pathways to of mitigate a symptom of substance abuse. The invention also provides methods and compositions for co-administration of modulators that act via the orexin and CRF pathways.