Cellular activation in limbic brain systems during social play behaviour in rats

Positive social interactions during the juvenile
and adolescent phases of life are essential for proper social
and cognitive development in mammals, including
humans. During this developmental period, there is a
marked increase in peer–peer interactions, signified by the
abundance of social play behaviour. Despite its importance
for behavioural development, our knowledge of the neural
underpinnings of social play behaviour is limited. Therefore,
the purpose of this study was to map the neural circuits
involved in social play behaviour in rats. This was
achieved by examining cellular activity after social play
using the immediate early gene c-Fos as a marker. After a
session of social play behaviour, pronounced increases in
c-Fos expression were observed in the medial prefrontal
cortex, medial and ventral orbitofrontal cortex, dorsal
striatum, nucleus accumbens core and shell, lateral amygdala,
several thalamic nuclei, dorsal raphe and the
pedunculopontine tegmental nucleus. Importantly, the
cellular activity patterns after social play were topographically
organized in this network, as indicated by playspecific
correlations in c-Fos activity between regions with
known direct connections. These correlations suggest
involvement in social play behaviour of the projections
from the medial prefrontal cortex to the striatum, and of
amygdala and monoaminergic inputs to frontal cortex and
striatum. The analyses presented here outline a topographically
organized neural network implicated in processes
such as reward, motivation and cognitive control
over behaviour, which mediates social play behaviour in
rats.