Elsevier

Legal Medicine

Volume 9, Issue 5, September 2007, Pages 251-257
Legal Medicine

The changes in AgNOR parameters of dorsal raphe nucleus neurons are related to suicide

https://doi.org/10.1016/j.legalmed.2007.02.001Get rights and content

Abstract

Depression has been established as the main cause of suicide and the research has concentrated on disturbed central serotonergic system in both disorders. The dorsal raphe nucleus (DRN) of brain stem is the main source of serotonergic innervation of limbic structures fundamental in the regulation of emotionally influenced behavior.

The study was carried out on paraffin-embedded brains from 10 depressive patients, among them 5 suicides and 5 non-suicides and 13 matched mentally healthy controls. The karyometric parameters of DRN neurons were evaluated by AgNOR (Argyrophilic Nucleolar Organizer) silver staining method.

The significant effect of suicide on nuclear area and AgNOR-ratio found in the cumulative analysis of all DRN subnuclei could be relevant for forensic diagnostic. The results suggest DRN neurons hypoactivity specific for suicide. Whether observed phenomenon is a “common trait” existing also in other diagnostic groups of mental disorders remains an open question.

Introduction

Suicide, which causes almost half of all violent deaths and results in nearly one million fatalities in the world every year, is rapidly becoming a public health problem of great magnitude. Studies from both developing and developed countries reveal an overall prevalence of mental disorders of 80–100% in cases of completed suicide and what is more, depression is most common among them [1]. Considering the recent neurobiological evidences, depression and suicide are distinct phenomena although share similarities and the unequivocally distinguishing diagnostic criteria have not yet been established [2], [3], [4], [5], [6]. They could be also important for the postmortem diagnostics of unclear forensic cases.

The disturbed serotonin neurotransmitter system is implicated in the etiology of depression, aggression, impulsivity and suicide [5], [7], [8], [9], [10], [11], [12], [13]. About 70% of neurons within the boundaries of the dorsal raphe nucleus (DRN) are serotonergic [14] and nearly all the large cells with long projecting fibers in this nucleus are serotonergic [15]. They provide the majority of serotonergic innervation to the medial prefrontal cortex and the nucleus accumbens which are key structures for the regulation of emotionally influenced behavior [14], [16], [17], [18]. A number of studies revealed biochemical and morphological changes in the DRN in suicide victims [6], [19], [20], [21], [22], [23], [24].

Nucleolar organizer (NOR) is the active region of nucleus, in which most of ribosomal synthesis occurs. NOR is composed of ribosomal DNA (rDNA) and proteins, some of which are argyrophilic. Argyrophilic nucleolar organizer (AgNOR) represents the site of ribosomal RNA synthesis and transcriptionally active NOR and is synonymous with the nucleolar area. Therefore, the cellular activity in terms of transcriptional activity of rDNA can be evaluated by measuring AgNOR [25], [26], [27], [28], [29], [30]. The relatively simple AgNOR staining method is well established in neuropathology [31], [32], [33], [34], [35], [36] and has been used both in forensic research and practice yet [35], [37]. The usefulness of AgNOR parameters in postmortem research has been proved in human brain [6], [38]. Recently, the AgNOR method has been applied to depression and suicide research [6] which could be also relevant for the forensic diagnostics.

Section snippets

Subject characteristics

Brains were collected postmortem from 10 patients with mood disorders (5 women, 5 men). The age range was 26–69 years. Of these, five subjects died by suicide, including 3 women and 2 men, ranging in age from 26 to 59 years. The methods of suicide were hanging (2), overdose of medication (1), incision of radial artery (1) and fall from the height (1). The determination of suicide was made by the Medical Examiner and verified by the investigators based on the individual records. The remaining

Results

After silver staining of DRN neurons, AgNOR (synonymous with the nucleolus) and nuclear borders are clearly visible within DRN neurons (Fig. 1). Most of the neurons contained one AgNOR; whereas, two or more AgNORs were observed very seldom.

The cumulative analysis of all DRN subnuclei was more informative than of particular subregions. The Kruskal–Wallis test revealed in this analysis a significant effect of suicide as a single factor on the mean values of nuclear area and AgNOR-ratio (P-values

Discussion

The present study revealed a significantly reduced nuclear area of DRN neurons paralleled by non-significantly reduced AgNOR area and number of depressive suicides vs non-suicides and controls. As regards the difference between suicides and other depressives, the results are consistent with those reported initially in DRN also on a small sample of cases [6]. However, this difference should be approached cautiously because of the unbalanced diagnostic composition (unipolar vs bipolar cases) of

Acknowledgments

The work described here was supported by grants of the Stanley Foundation, the Deutsche Forschungsgemeinschaft (DFG 799/6-1), the Bundesministerium für Bildung und Forschung (BMBF NBL-3/2 and 01ZZ0407) and the Alfried-Krupp-von-Bohlen-und-Halbach Stiftung.

We thank S. Funke and H. Dobrowolny for the excellent technical assistance.

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