The submitted article comprises the basic knowledge dealing with pathophysiological theories of depression and with hypotheses on the mechanism of pharmacological action of antidepressant drugs and their development over the last several decades: from depletion hypotheses to the theory of neuroplasticity.

        Key words: depression - pathophysiology - antidepressants - therapy - neurotransmitters - noradrenaline - serotonin - reuptake inhibitors - MAO inhibitors - receptor hypersensitivity - neuroplasticity - CREB - BDNF.