The N-methyl-D-aspartate (NMDA) receptor antagonist ketamine is a robust, rapid-acting antidepressant whose molecular effects have not been fully elucidated. Phosphodiesterase-4 (PDE4), which terminates cyclic adenosine monophosphate (cAMP) activity, may underlie antidepressant response. In particular, previous studies found that whole brain binding of the positron emission tomography (PET)...
Chronic cannabis (marijuana, hashish) smoking can result in dependence. Rodent studies show reversible downregulation of brain cannabinoid CB1 (cannabinoid receptor type 1) receptors after chronic exposure to cannabis. However, whether downregulation occurs in humans who chronically smoke cannabis is unknown. Here we show, using positron emission tomography imaging, reversible and regionally...