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September 1996

Immunodetection and Quantitation of Imidazoline Receptor Proteins in Platelets of Patients With Major Depression and in Brains of Suicide Victims

Author Affiliations

From the Department of Psychiatry, Medical School, University of Geneva, Geneva, Switzerland (Drs García-Sevilla, Walzer, Jaquet, and Guimón); Laboratory of Neuropharmacology, Department of Fundamental Biology and Health Sciences, University of the Balearic Islands, Palma de Mallorca, Spain (Drs García-Sevilla, Escriba, Sastre, and Busquets); and Division of Neurobiology, Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY (Dr Reis).

Arch Gen Psychiatry. 1996;53(9):803-810. doi:10.1001/archpsyc.1996.01830090049008

Background:  Imidazoline receptors are a newly discovered family of receptors, some of which, like α2adrenoceptors, have a presynaptic inhibitory effect on the release of norepinephrine. The aim of this study was to identify by immunodetection imidazoline receptor proteins in human platelets and the brain to assess their status in depression and suicide.

Methods:  Platelets were collected from 26 drug-free depressed patients and 26 controls. Specimens of frontal cortex (Brodmann area 9) were collected from 13 suicide victims and 11 controls. Levels of imidazoline receptor proteins were assessed by immunoblotting techniques. Solubilized imidazoline receptors were separated by gel electrophoresis, transferred to nitrocellulose membranes, labeled with a specific anti—imidazoline receptor antiserum, and quantitated by image analysis.

Results:  Platelet and brain membranes expressed similar 45-kd imidazoline receptor proteins, and their mean ± SEM immunoreactivities were found to be increased in depressed patients (platelets, 40%±5%) and suicide victims (brain, 51%±14%). Platelets also expressed a 35-kd imidazoline receptor protein that was also found to be up-regulated in depressed patients (21%±4%). In contrast, brain membranes did not express this 35-kd protein but revealed a 29/30-kd imidazoline receptor protein that was found to be down-regulated in suicide victims (19%±3%). In a subset of depressed patients who underwent antidepressant treatment, a change in the immunoreactivity of the up-regulated 45-kd platelet imidazoline receptor protein (-35%±5%), but not of the 35-kd protein, was observed.

Conclusion:  The results support a role for the newly discovered imidazoline receptors (mainly the 45-kd receptor expressed in the brain and platelets) in the pathogenesis of depression.

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