Apomorphine-induced sensitization in rats exposed to restraint stress: Relationship with adaptation to stress

Drug abuse and impaired adaptation to stress are inter-related. Drug abuse is more potentiated upon exposure to stress and an impairment to cope with stress may lead to depression. On the other hand, use of addictive compounds increase the vulnerability to depression by inhibiting the adaptation to stress. Present study investigates relationship between behavioral tolerance to repeated restraint stress and apomorphine-induced sensitization. Apomorphine was injected either before or after the restraint stress episode, to monitor drug-induced behavioral sensitization and place preference. Apomorphine-induced sensitization and place preference were enhanced if the drug is experiencing during restraint stress. Conversely, apomorphine-induced sensitization and place preference were attenuated if the drug is experiencing after restraint stress. It shows that apomorphine, if experienced during restraint stress, produces greater sensitization Conversely, sensitization effects of apomorphine are blocked in animals receiving apomorphine after the termination of restraint stress. The results tend to show that drug of abuse may be effective for the treatment but not prevention of stress-induced depression.