Growth hormone response to clonidine and cortisol secretion pattern predict changes in peripheral blood lymphocyte subsets in major depressive patients

Mitogen stimulated rise of intracellular calcium concentration in single T lymphocytes from patients with major depression is reduced

1. The authors investigated the signal transduction in T-lymphocytes as a peripheral model for central neurons. 2. Intracellular free calcium concentration [Ca2+]i was measured using fura 2 in T-lymphocytes from 6 patients with major depression during and after depression and from 6 healthy controls. Patients were treated with interpersonal therapy (IPT) but not with psychotropic medication. 3. Phytohemagglutinin (PHA) triggers an oscillatory [Ca2+]i signal in human T-lymphocytes. This implies two mechanisms for [Ca2+]i regulation: inositol phophate (IP) mediated release from intracellular stores and [Ca2+]i influx from the extracellular medium. 4. PHA stimulates 49% of T cells from controls but only 17% of T cells from depressed patients. This finding explains previous results from cells in suspension indicating that [Ca2+]i signals after PHA-stimulation are reduced in cells from depressed patients. 5. Cells from depressed patients show less [Ca2+]i oscillations. Normal oscillation patterns are restored after clinical recovery from depression. 6. Thus altered [Ca2+]i oscillations in T-lymphocytes are a state phenomenon and may give us clues where to search for altered cellular mechanisms during depression.

Biological aspects of depression

In most cases, depression involves the interaction of biological and psychosocial factors. The impact of biological factors seems to be more prominent in major depressive syndrome, where typical symptoms and signs such as decrease in weight, changes in libido, dysmenorrhea, and sleeping disorders cannot be explained on psychodynamic grounds alone. Some of the symptoms and signs typical of patients suffering from depression reflect a primary disorder of biochemical and neurophysiological functions and are not commonly found in other forms of psychic disturbances. Studies related to monoamine (noradrenaline, serotonin or 5-HT, dopamine) metabolism have assumed a major role in biochemical research into depression; this research now also includes studies on other central neurotransmitters such as GABA and glutamic acid, and neuropeptides like somatostatin and corticotropin-releasing factor (CRF). Several theories have been suggested for the biochemical background of depression, and these hypotheses can now be tested using new and sophisticated research methods. Recent progress in understanding receptor structure and function and the regulation of neuroendocrine functions will substantially increase our knowledge of the biological deviations in depression and eventually lead to better drugs and treatment strategies. In the following, current perspectives on the biology of depressive disorders are introduced. It seems clear that susceptibility to depression is linked with deviations in presynaptic and postsynaptic neurotransmitter turnover and function. These, in turn, may lead to alterations in other regulatory mechanisms, such as the neuroendocrine and immune systems.