Cannabinoids modulation of emotional and non-emotional memory processes after stress

The endocannabinoid system (ECS) is involved in regulating the stress response and subsequent changes in neuroendocrine function and emotional behavior. It is also a critical neuromodulatory system that affects learning and memory. Generally systemically administered cannabinoid agonists have an impairing effect on memory processes although enhancing effects are also reported. Stress is a potent modulator of brain function and cognition that has differential effects on memory function depending on a number of factors (such as stress duration, stress intensity, timing and the source of the stress, as well as the learning type under study). Most of the tasks to investigate learning and memory in laboratory rodents are stressful for the animals (i.e. the cognitive task includes intrinsic stress) as opposed to extrinsic stress which refers to outside stress that occurs before or after the cognitive task. Several lines of evidence suggest that cannabinoids differentially affect different memory phases (acquisition, consolidation, retrieval and extinction), and that the type of cognitive task (emotional or aversive versus non-emotional) also determines the neural substrates underlying the effects of cannabinoids on memory. In this chapter I will describe the interaction between the effects of activating the ECS and stress exposure on emotional (i.e., aversive) and non-emotional learning and memory processes in animal models. I will argue that administering cannabinoid agonists in proximity to extrinsic stress exposure normalizes stress modulation of emotional memory. A possible model of the effects of cannabinoids on emotional memory after stress is also presented.