Pavel D. Hrdina

Dysregulation in the Suicide Brain: mRNA Expression of Corticotropin-Releasing Hormone Receptors and GABAA Receptor Subunits in Frontal Cortical Brain Region

Corticotropin-releasing hormone (CRH) and GABA have been implicated in depression, and there is reason to believe that GABA may influence CRH functioning. The levels of CRH, and mRNA for CRH-binding protein, CRH1, and CRH2 receptors, as well as various GABAA receptor subunits (α1, α2, α3, α4, α5, δ, and γ2), were determined in several frontal cortical brain regions of depressed suicide victims and nondepressed individuals who had not died by suicide. Relative to the comparison group, CRH levels were elevated in frontopolar and dorsomedial prefrontal cortex, but not in the ventrolateral prefrontal cortex of suicide victims. Conversely, using quantitative PCR analyses, it was observed that, in frontopolar cortex, mRNA for CRH1, but not CRH2, receptors were reduced in suicide brains, possibly secondary to the high levels of CRH activity. In addition, mRNA of the α1, α3, α4, and δ receptor subunits was reduced in the frontopolar region of suicide victims. Interestingly, a partial analysis of the GABAA receptor functional genome revealed high cross-correlations between subunit expression in cortical regions of nondepressed individuals, suggesting a high degree of coordinated gene regulation. However, in suicide brains, this regulation was perturbed, independent of overall subunit abundance. These findings raise the possibility that the CRH and GABAA receptor subunit changes, or the disturbed coordination between these GABAA receptor subunits, contribute to depression and/or suicidality or are secondary to the illness/distress associated with it.

5-HT uptake sites and 5-HT2 receptors in brain of antidepressant-free suicide victims/depressives : increase in 5-HT2 sites in cortex and amygdala

The density (Bmax) of 5-HT2 receptors labelled with [3H]ketanserin was significantly increased in prefrontal cortex (by 67%) and amygdala (by 97%) from suicide/depressives in comparison with controls. There were no differences in Kd of [3H]ketanserin binding between the two groups. The density (Bmax) and affinity (Kd) of [3H]paroxetine sites were not significantly different in the suicide/depressives and controls. The ratio between the density of presynaptic 5-HT uptake sites and postsynaptic 5-HT2 receptors in amygdala was significantly lower in suicide/depressives than in controls. The data confirm and extend some of the previous findings of increases in 5-HT2 receptors in post-mortem brains of suicide victims and depressives who died of natural causes and lend support to the view that an abnormality in brain serotonergic system is associated with depression and suicidal behaviour.

Association of polymorphism of serotonin 2A receptor gene with suicidal ideation in major depressive disorder

There is evidence indicating that density of 5-HT2A receptors is altered in brain regions of depressed suicide victims and in platelets of suicidal subjects with major depression or schizophrenia. Recent studies have also shown an association between the allele C of 102T/C polymorphism in the 5-HT2A receptor gene and schizophrenia. The present investigation tested the hypothesis that the observed changes in 5-HT2A receptor density in platelets of patients with major depression are a trait rather than state phenomenon and are associated with the 102 C allele in 5-HT2A receptor gene in a sample of 120 patients with major depression and a group of 131 control subjects comparable with respect to age, sex, and ethnic background. The allele and genotype frequencies of 102T/C polymorphism in 5-HT2A receptor gene were compared between patients and control subjects and between suicidal and non-suicidal patient groups. The major finding of this study was a significant association between the 102 C allele in 5-HT2A receptor gene and major depression, chi(2) = 4.5, df = 1, P = 0.03, particularly in patients with suicidal ideation, chi(2) = 8.5, df = 1, P < 0.005. Furthermore, we found that patients with a 102 C/C genotype had a significantly higher mean HAMD item 3 score (indication of suicidal ideation) than T/C or T/T genotype patients. Our results suggest that the 102T/C polymorphism in 5-HT2A receptor gene is primarily associated with suicidal ideation in patients with major depression. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:56-60, 2000.

Corticotropin-releasing hormone, arginine vasopressin, gastrin-releasing peptide, and neuromedin B alterations in stress-relevant brain regions of suicides and control subjects.

BACKGROUND Postmortem levels of several stress- and depression-relevant neuropeptides were assessed in brain regions of depressed suicides relative to control subjects that had died of other causes. METHODS Brains of suicides and those that died from other causes were collected soon after death (typically <6 hours). Immunoreactivity levels (ir) of corticotropin-releasing hormone (CRH-ir) and arginine vasopressin (AVP-ir), and the bombesin analogs, gastrin-releasing peptide (GRP-ir), and neuromedin B (NMB-ir), were assessed. RESULTS Levels of CRH-ir among suicides were elevated in the locus coeruleus (LC), frontopolar, dorsolateral prefrontal (DMPFC) and ventromedial prefrontal cortices, but were reduced at the dorsovagal complex (DVC). The concentration of AVP-ir was elevated at the paraventricluar hypothalamic nucleus, LC, and DMPFC, and reduced at the DVC. Finally, GRP and NMB variations, which might influence anxiety states, were limited, although GRP-ir within the LC of suicides was higher than in control subjects, while NMB-ir was reduced at the DVC of suicides. CONCLUSIONS The data show several neuropeptide changes in relation to suicide, although it is premature to ascribe these outcomes specifically to the suicide act versus depression. Likewise, it is uncertain whether the neuropeptide alterations were etiologically related to suicide/depression or secondary to the depressive state.

High activity-related allele of MAO-A gene associated with depressed suicide in males

Abnormalities in brain monoamine oxidase A activity have been implicated in the pathogenesis of depressive illness and suicidal behavior. The present investigation was to determine whether there is an association between MAO-A gene polymorphism and depressed suicide. The Eco RV polymorphism in MAO-A gene with alleles associated with enzyme activity was studied in postmortem brain samples from 44 depressed suicide victims and 92 control subjects of the same ethnic background. We have found significant differences in genotype/allele distribution between depressed suicide victims and controls in males (p  = 0.012) but not in females or the total sample. The odds ratio (OR) for the high activity-related allele of the MAO-A gene associated with depressed suicide in males was 3.1. Our finding suggests that MAO-A may be a susceptibility gene in depressed male suicide victims. The results thus provide further evidence that genetic factors can modulate risk for depression, suicide or both by influencing monoaminergic activity in sexually dimorphic manner.

Platelet serotonergic indices in major depression: up-regulation of 5-HT2A receptors unchanged by antidepressant treatment

This study examined, in the largest sample of major depressives reported so far, platelet serotonergic parameters (5-HT uptake, [3H]paroxetine binding and 5-HT2A receptors measured by [3H]LSD binding) in 60 antidepressant-free depressed patients and 40 age- and gender-matched control subjects before treatment, and in 45 major depression patients during treatment with antidepressants. We found that, at baseline, the density (Bmax) of 5-HT2A receptors was significantly higher (by 39%) in depressed patients than in controls. Suicidal patients had significantly higher Bmax values than controls or non-suicidal patients. The rate of serotonin uptake (Vmax), but not the uptake at a single concentration, was significantly higher in depressed patients, particularly in females. There was no significant difference between the Kd or Bmax of [3H]paroxetine binding in control and depressed subjects. Treatment with antidepressant drugs of different pharmacological profile had no significant effect on the density of 5-HT2A receptors, nor did the receptor number predict the response to treatment. The affinity of serotonin uptake site for 5-HT and [3H]paroxetine significantly decreased during treatment with antidepressants, particularly SSRIs. Suppression of 5-HT uptake correlated with decreases in Hamilton depression (HAMD) scores. Our data suggest that the increased density of platelet 5-HT2A receptors may be associated with untreated major depression in antidepressant-free depressed patients, in particular those with suicidal thoughts. The persistence after antidepressant treatment and clinical improvement would suggest that up-regulation of 5-HT2A receptors is a trait rather than state phenomenon. Correlation of 5-HT uptake suppression with decreases in HAMD scores suggests that serotonin uptake inhibition is a relevant factor in antidepressant drug effect and clinical improvement.

Effects of selective serotonin reuptake inhibitors on platelet serotonin parameters in major depressive disorder

The effects of treatment with serotonin (5-HT) reuptake inhibitors on platelet 5-HT2 receptors, 5-HT reuptake sites an 5-HT uptake were studied in a double-blind trial comparing two selective serotonin reuptake inhibitors (SSRI), paroxetine, and fluoxetine, for the treatment of major depression. Hamilton Depression Rating Scale (HAM-D) scores and platelet 5-HT parameters were determined in 21 depressed patients at baseline, after 4 and 8 weeks of treatment, and were compared to 21 healthy controls. Antidepressant treatment did not significantly alter the density of 5-HT reuptake sites, labelled with [3H]paroxetine, or 5-HT2 receptors, labelled with [3H]LSD. However, a strong correlation was observed between the HAM-D suicidality item and 5-HT2 receptor density at baseline. A marked increase in platelet 5-HT2 receptors at baseline was observed in suicidal depressed patients compared to those with no suicidal ideation and healthy controls. Changes in [3H]paroxetine Bmax and in [3H]5-HT uptake significantly correlated with change in HAM-D score at 4 and 8 weeks respectively. These results confirm previous reports of an association between suicidality and platelet 5-HT2 receptor upregulation. Our data also lends support to the use of platelet 5-HT parameters as indicators of antidepressant efficacy, particularly in suicidal depressed patients.

Differentiation of two components of specific [3H]imipramine binding in rat brain

Specific binding of [3H]imipramine to membrane preparation from rat cerebral cortex can be resolved in two distinct components: the high-affinity binding with a KD in nanomolar range (6.9 +/- 0.4 nM) and a maximum number of binding sites (Bmax) 285 +/- 19 fmol/mg protein and the low-affinity component with a KD of 292 +/- 45 nM and Bmax of 2459 +/- 428 fmol/mg protein. Tricyclic antidepressants, a non-tricyclic serotonin uptake inhibitor fluoxetine and a tetracyclic antidepressant maprotiline show a markedly different pattern in displacing [3H]imipramine binding at the high- and the low-affinity site. When the high-affinity sites were protected, the differences in potency of tested drugs in displacing specific [3H]imipramine binding, and the correlation with their ability to inhibit serotonin reuptake, were not observed. The Hill coefficients of competing drugs at low-affinity sites were markedly lower (0.45-0.69) and the shape of displacement curves indicated that more than one site may be involved in low affinity binding of [3H]imipramine.

Protein kinase C in rat brain cortex and hippocampus: effect of repeated administration of fluoxetine and desipramine.

1 Recent evidence indicates that changes in the activity of cyclic AMP‐dependent protein kinase may be involved in neuroadaptive mechanisms after chronic treatment with antidepressants. The aim of this study was to investigate the effect of repeated administration of fluoxetine (FL) and desipramine (DMI) on the distribution and activity of protein kinase C (PKC) in subcellular fractions of rat cortex (Cx) and hippocampus (Hc) under basal conditions and in response to a single in vivo administration of 5‐HT2A/2C agonist, 1‐(2,5‐dimethoxy‐4‐iodophenyl)‐2‐aminopropane (DOI). 2 Rats were treated for 21 days with FL (5 mg kg−1 day−1, i.p.) or DMI (10 mg kg−1 day−1, i.p.). DOI was injected to groups of rats receiving repeated doses of antidepressants or to control rats 1 h before ex vivo PKC assay. Distribution of PKC was determined by [3H]‐phorbol‐12,13‐dibutyrate ([3H]‐PDBu) binding and PKC activity by the Amersham enzyme assay system. 3 Autoradiography of tissue sections revealed decreased [3H]‐PDBu binding in CA1 region of hippocampus (by 18%) and paraventricular thalamic nucleus (by 28%) of rats after repeated administration of FL. 4 In vitro exposure of brain sections to 50 μm FL resulted in significant decreases (by 23–32%) of [3H]‐PDBu binding in six out of seven regions examined; exposure to 100 μm FL reduced [3H]‐PDBu binding (by 36–52%) in all regions. In contrast, exposure of brain sections to 100 μm DMI failed to alter specific [3H]‐PDBu binding in brain sections. 5 The activity of PKC in subcellular fractions of Cx and Hc was significantly (by 40–50%) decreased in rats given repeated doses of FL or DMI. A single administration of either drug was without effect. 6 A single in vivo administration of DOI to control rats resulted in reduced PKC activity (by 30–40%) in the particulate fraction of both Cx and Hc. This response to DOI was similar in DMI‐treated rats but was not seen in rats given repeated doses of FL. A single administration of DOI to animals given repeated doses of FL resulted in PKC activities higher than those seen in rats treated with FL alone. 7 The results indicate that repeated administration of FL and DMI produced similar changes in basal PKC activity but differentially affected the PKC response to the 5‐HT2A/2C receptor agonist, DOI. The effect on basal PKC activity may result from a post‐receptor action of antidepressants; the alteration of PKC response to DOI after fluoxetine could be due to receptor‐mediated desensitization of the signalling system.

Lead in blood and brain regions of rats chronically exposed to low doses of the metal

Abstract The concentration of lead in blood and cerebral cortex (Cx), striatum (St), hippocampus (Hc), and midbrain (Mb) was measured by flameless atomic absorption spectrophotometry in rats that had received (po) daily 0.005, 0.025, 0.1, or 1.0 mg lead/kg from 3 days until 4, 6, or 8 weeks of age. The blood lead levels and regional brain lead content of control rats increased with age. In addition to a dose-dependent increase in blood lead levels of rats exposed to 0.1 mg lead/kg (by 176%) and 1.0 mg lead/kg (by 396%), the concentration of the metal in blood of rats treated with the 0.1 mg/kg dose initially increased with the duration of exposure, reached a maximum value of 13.8 μg/dl at 6 weeks of age, and leveled off thereafter. Whereas exposure to small amounts of lead (0.025 mg/kg) resulted in a preferential accumulation of lead in the Hc (by 127%), a larger dose of the metal (0.1 mg/kg) administered for the same period of time produced significant increases in the lead content of the Cx (by 80%), St (by 106%), Hc (by 134%), and Mb (by 67%); no significant interregional differences in lead content were noted. The duration of treatment also influenced the distribution of lead. Exposure to 0.1 mg lead/kg for 4 weeks resulted in a significant increase in the lead levels of only the Cx (by 125%) and Hc (by 522%), while the same treatment for 8 weeks resulted in a significant and similar accumulation of lead in all of the regions examined. These data indicate that in the case of chronic low-level lead poisoning, brain regional lead distribution is influenced by both the dose of the metal administered and the duration of exposure. Significant amounts of lead persisted in brain tissue for as long as 2 and 4 weeks after the withdrawal of lead treatment.