Postreceptor pathways for signal transduction in depression and bipolar disorder.

Study of the norepinephrine pathway has elucidated the pathophysiology of depression and bipolar disorder. Various elements along this pathway, including adrenoreceptors, G proteins, cyclic adenosine monophosphate (AMP), cyclic AMP regulatory element binding protein and brain-derived neurotrophic factor, have been identified as potential targets for antidepressants and mood-stabilizing drugs. The results of a wide range of research in this area, along with the hypotheses now under investigation, are summarized in this paper.