Investigando fenótipos comportamentais e eletrofisiológicos associados ao estresse social
The aims of this thesis were to investigate behavioral and electrophysiological patterns associated to resilience and susceptibility to social stress in mice. For this, we used a chronic social defeat stress protocol based on the resident-intruder paradigm. The results are presented here in two st...
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| Formato: | doctoralThesis |
| Idioma: | por |
| Publicado em: |
Brasil
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/21620 |
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| Resumo: | The aims of this thesis were to investigate behavioral and electrophysiological patterns associated to
resilience and susceptibility to social stress in mice. For this, we used a chronic social defeat stress
protocol based on the resident-intruder paradigm. The results are presented here in two studies. In the
first study, C57BL/6J mice submitted to repeated social defeat episodes showed delayed motivation to
interact with an unfamiliar conspecific in long duration (10 min) sessions of the social interaction test.
By using an ethological approach combined with computational video analysis, it was possible to track
precisely the mouse position during social investigation behavior performance. With that approach, it
was analyzed the detailed expression of defensive behaviors, such as stretched attended postures and
flights, both associated to social investigation behaviors. From these analyzes, it was demonstrated
that social investigation behaviors based on stretched attend postures were significantly higher in
defeated mice in comparison to controls. Still, a subpopulation of defeated mice showed persistently
and non-habituating stretched attend postures during social investigation. By using a measure based on
the investigation distance during social investigations, it was possible to compute an approach index
(AI) to each animal and separate a subpopulation showing an anxiety-related phenotype. The flight
incidence was also increased in defeated group as compared with controls. The persistent occurrence
of this behavior was observed in a subpopulation of defeated mice. We calculated a flight index (FI)
that inversely correlated with sucrose preference, showing to be useful to identify anhedonic animals.
In the second study, we combined ethological approach and electrophysiological recordings in the
ventral tegmental area of mice submitted to chronic social defeat stress. By using electrophysiological
and pharmacological criteria, single-units recorded from the ventral tegmental area were classified as
putative dopaminergic and non-dopaminergic neurons. During the social investigation behavior it was
observed that firing rate modulations of distinct neuronal subpopulations occurred in opposite manner
in social defeat susceptible and resilient mice. In summary, this work proposes that longer sessions of
the social interaction test associated to ethological approach can provide information for the
behavioral classifications of resilient and susceptible mice after social defeat stress. Furthermore, the
expression of susceptible phenotype could be related to the midbrain dopaminergic system impairment
in the incentive value assignment to social interactions normally associated with increased mesolimbic
neuronal activity. |
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