Regulation of 5-HT receptors and the hypothalamic-pituitary-adrenal axis.
Implications for the neurobiology of suicide
by
Lopez JF, Vazquez DM, Chalmers DT, Watson SJ
Department of Psychiatry,
University of Michigan Medical Center,
Ann Arbor,
USA.
jflopez@umich.edu
Ann N Y Acad Sci 1997 Dec 29; 836:106-34
ABSTRACT
Disturbances in the serotonin (5-HT) system is the neurobiological
abnormality most consistently associated with suicide. Hyperactivity of the
hypothalamic-pituitary-adrenal (HPA) axis is also described in suicide victims.
The HPA axis is the classical neuroendocrine system that responds to stress and
whose final product, corticosteroids, targets components of the limbic system,
particularly the hippocampus. We will review results from animal studies that
point to the possibility that many of the 5-HT receptor changes observed in
suicide brains may be a result of, or may be worsened by, the HPA overactivity
that may be present in some suicide victims. The results of these studies can be
summarized as follows: (1) chronic unpredictable stress produces high
corticosteroid levels in rats; (2) chronic stress also results in changes in
specific 5-HT receptors (increases in cortical 5-HT2A and decreases in
hipocampal 5-HT1A and 5-HT1B); (3) chronic antidepressant administration
prevents many of the 5-HT receptor changes observed after stress; and (4)
chronic antidepressant administration reverses the overactivity of the HPA axis.
If indeed 5-HT receptors have a partial role in controlling affective states,
then their modulation by corticosteroids provides a potential mechanism by which
these hormones may regulate mood. These data may also provide a biological
understanding of how stressful events may increase the risk for suicide in
vulnerable individuals and may help us elucidate the neurobiological
underpinnings of treatment resistance.
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