Human urinary biogenic amines and some physiological responses during situation stress

Stress-induced aggression in heterozygous TPH2 mutant mice is associated with alterations in serotonin turnover and expression of 5-HT6 and AMPA subunit 2A receptors

BACKGROUND

The contribution of gene-environment interactions that lead to excessive aggression is poorly understood. Environmental stressors and mutations of the gene encoding tryptophan hydroxylase-2 (TPH2) are known to influence aggression. For example, TPH2 null mutant mice (Tph2-/-) are naturally highly aggressive, while heterozygous mice (Tph2+/-) lack a behavioral phenotype and are considered endophenotypically normal. Here we sought to discover whether an environmental stressor would affect the phenotype of the genetically 'susceptible' heterozygous mice (Tph2+/-).

METHODS

Tph2+/- male mice or Tph2+/+ controls were subjected to a five-day long rat exposure stress paradigm. Brain serotonin metabolism and the expression of selected genes encoding serotonin receptors, AMPA receptors, and stress markers were studied.

RESULTS

Stressed Tph2+/- mice displayed increased levels of aggression and social dominance, whereas Tph2+/+ animals became less aggressive and less dominant. Brain tissue concentrations of serotonin, its precursor hydroxytryptophan and its metabolite 5-hydroxyindoleacetic acid were significantly altered in all groups in the prefrontal cortex, striatum, amygdala, hippocampus and dorsal raphe after stress. Compared to non-stressed animals, the concentration of 5-hydroxytryptophan was elevated in the amygdala though decreased in the other brain structures. The overexpression of the AMPA receptor subunit, GluA2, and downregulation of 5-HT6 receptor, as well as overexpression of c-fos and glycogen-synthase-kinase-3β (GSK3-β), were found in most structures of the stressed Tph2+/- mice.

LIMITATIONS

Rescue experiments would help to verify causal relationships of reported changes.

CONCLUSIONS

The interaction of a partial TPH2 gene deficit with stress results in pathological aggression and molecular changes, and suggests that the presence of genetic susceptibility can augment aggression in seemingly resistant phenotypes.

The effect of motivation on shoulder-muscle tension in attention-demanding tasks

This paper evaluates motivation as a task-related factor causing the development of psychologically mediated ('psychogenic') shoulder-muscle tension. In four separate experiments using a visual display unit (VDU) based complex reaction-time task, motivation was established by means of continuous feedback on the level of performance (relative to a preset target performance level) or by means of a money reward for good performance. In all experiments motivation improved the performance, but an increase in the psychogenic shoulder-muscle tension was only observed in the money-reward condition. It is discussed whether this difference in the muscle-tension response is due to changes in the subjects' attitude unrelated to performance or due to a superior performance in the money-reward condition.

Comparison of panic disordered patients with high versus low MHPG

Fourteen panic disorder patients with low 3-methoxy-4-hydroxyphenylglycol (MHPG) were compared to 14 patients with high MHPG. Patients with low MHPG were more likely during the preceding month to have experienced spontaneous panic attacks (P less than 0.008) than were patients with high MHPG. Patients with high MHPG had increased severity ratings on several individual symptoms of anxiety.

Activation in professional ballet dancers

The purpose of the study was to examine professional ballet dancers' psychophysiological activation in different types of rehearsal and performance. Electrical activity of the trapezius muscle (EMG), blood pressure, heart rate, and skin conductance level were measured. Self-estimated mental tension was evaluated, as was success in the performance. The effect of sex, age, professional experience, artistic status, role, and type of rehearsal and performance was studied. Principals had lower EMG at rest than soloists or corps de ballet dancers. The principals' psychophysiological activation during performance was increased more than that of soloists or corps de ballet dancers as compared to the values at rest. The type of performance had an effect on self-estimated mental tension and psychophysiological responses. During the last general rehearsals (with an audience) physiological activation was higher than on first nights or in other performances or rehearsals.