Required for normal development of ethanol tolerance. Relies on two distinct molecular pathways: a cellular stress pathway defined by hang, and a parallel pathway requiring octopamine. Expressed ubiquitously in the nervous system, in neurons not glia. Flies exhibit defective responses to environmental stressors, such as heat and the free-radical-generating agent paraquat. Stress, at both the cellular and systemic levels, contributes to drug- and addiction-related behaviors in mammals. Function of hang suggests that this role may be conserved across evolution.