Immunodetection and quantitation of imidazoline receptor proteins in platelets of patients with major depression and in brains of suicide victims.
BACKGROUND
Imidazoline receptors are a newly discovered family of receptors, some of which, like alpha 2-adrenoceptors, 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.


CONCLUSIONS
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.
García-Sevilla
J A
JA
Department of Psychiatry, Medical School, University of Geneva, Switzerland.
Escribá
P V
PV
Sastre
M
M
Walzer
C
C
Busquets
X
X
Jaquet
G
G
Reis
D J
DJ
Guimón
J
J
D000328:Adult; D000368:Aged; D000928:Antidepressive Agents / Q000494:pharmacology / Q000627:therapeutic use; D001792:Blood Platelets / Q000737:chemistry*; D015153:Blotting, Western; D001923:Brain Chemistry; D003866:Depressive Disorder / Q000097:blood* / Q000188:drug therapy / Q000209:etiology; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000032:analysis*; D054755:Imidazoline Receptors; D008297:Male; D008875:Middle Aged; D011955:Receptors, Drug / Q000032:analysis* / Q000187:drug effects; D013405:Suicide / Q000706:statistics & numerical data*; D014404:Tubulin / Q000032:analysis; D015854:Up-Regulation
D000928:Antidepressive Agents; D007093:Imidazoles; D054755:Imidazoline Receptors; D011955:Receptors, Drug; D014404:Tubulin