Role of the endocannabinoid system in regulation of the hypothalamic-pituitary-adrenocortical axis

The endocannabinoid system has been recognized as a major neuromodulatory system, which functions to maintain brain homoeostasis. Endocannabinoids are synthesized and released from the postsynapse and act as retrograde neuronal messengers, which bind to cannabinoid type 1 receptors at the presynapse. Here, they inhibit the release of neurotransmitters, including glutamate and GABA. By these means, endocannabinoids control the activation of various neuronal circuits including those involved in neuroendocrine stress processing. Accordingly, exogenous cannabinoids such as the major active component of marijuana, Delta(9)-tetrahydrocannabinol, have long been known to activate the major neuroendocrine stress response system of mammals, the hypothalamic-pituitary-adrenocortical (HPA) axis. However, the function of the endocannabinoid system in the regulation of stress hormone secretion has only recently begun to be understood. It is the focus of the present review to provide the reader with an overview of our current knowledge of the role of endocannabinoid signalling in HPA axis regulation under basal as well as under stressful conditions. This includes the specific sites of action, potential underlying neuronal pathways and interactions between behavioural and neuroendocrine stress coping. Furthermore, the potential role of HPA axis activity dysregulations, caused by deficits in the endocannabinoid system, for the pathophysiology of psychiatric diseases is discussed.