Quantified tracking and monitoring of diazepam treated socially housed cynomolgus monkeys.

Quantitative assessment of behavioural patterns is frequently used in rodent toxicity studies, however only limited approaches are available for monkeys. Often qualitative behavioural scoring using functional observation batteries (FOBs) is performed, with difficulties like poor reproducibility or lack of sensitivity. In this study, we investigated whether quantitative behavioural monitoring can be applied to group-housed cynomolgus monkeys. Video-tracking EthoVision® XT system and special analysis software were used to evaluate diazepam (i.v. 1mg/kg) related behavioural changes in group-housed animals. Recordings were made predose and at the anticipated time of maximum drug exposure (T(max)). General parameters such as distance travelled and velocity did not reveal the known sedative effects of diazepam. However, inspection of the automatically generated track images indicated that diazepam-treated animals had more a meandering movement pattern suggesting that diazepam induced a loss of balance which was regained by corrective movements. Therefore, parameters revealing specific aspects of the meandering movement pattern such as velocity profiles and turn angles have been analyzed and revealed an increase in the curvature and in the number of directional changes of the movement path.

Reduced 5-HT1A- and GABAB receptor function in dorsal raphé neurons upon chronic fluoxetine treatment of socially stressed rats.

Autoinhibitory serotonin 1A receptors (5-HT(1A)) in dorsal raphé nucleus (DRN) have been implicated in chronic depression and in actions of selective serotonin reuptake inhibitors (SSRI). Due to experimental limitations, it was never studied at single-cell level whether changes in 5-HT(1A) receptor functionality occur in depression and during SSRI treatment. Here we address this question in a social stress paradigm in rats that mimics anhedonia, a core symptom of depression. We used whole cell patch-clamp recordings of 5-HT- and baclophen-induced G-protein-coupled inwardly rectifying potassium (GIRK) currents as a measure of 5-HT(1A)- and GABA(B) receptor functionality. 5-HT(1A)- and GABA(B) receptor-mediated GIRK-currents were not affected in socially stressed rats, suggesting that there was no abnormal (auto)inhibition in the DRN on social stress. However, chronic fluoxetine treatment of socially stressed rats restored anticipatory behavior and reduced the responsiveness of 5-HT(1A) receptor-mediated GIRK currents. Because GABA(B) receptor-induced GIRK responses were also suppressed, fluoxetine does not appear to desensitize 5-HT(1A) receptors but rather one of the downstream components shared with GABA(B) receptors. This fluoxetine effect on GIRK currents was also present in healthy animals and was independent of the animal's "depressed" state. Thus our data show that symptoms of depression after social stress are not paralleled by changes in 5-HT(1A) receptor signaling in DRN neurons, but SSRI treatment can alleviate these behavioral symptoms while acting strongly on the 5-HT(1A) receptor signaling pathway.

Defeat followed by individual housing results in long-term impaired reward- and cognition-related behaviours in rats.

In contrast to the well-documented acute effects on behavioural sensitivity, chronic effects that persist for weeks or even months after the cessation of the stressor received relatively little attention. This study aimed at the long-term effects of a severe stressor, i.e. social defeat followed by individual housing. Defeated and subsequently individually housed animals displayed impaired social memory, decreased social interaction and diminished anticipation for a sucrose solution for up until a period of 3 months after defeat. Remarkably, social housing counteracted the defeat-induced effects. The impaired capability to anticipate for a reward was discussed in relation to anhedonia, an important symptom of human depression. Moreover, the disturbed memory, the chronic nature of the effects, and the therapeutic effects of social housing, suggest that the defeat model may serve as a potential model for human psychopathology.