Neural Activity In Amygdala Subdivisions Evoked By Periodic And/Or Single Enriching Experiences In Adolescent Rats

Adolescence is often a stressful period of time marked with low cognitive control, high emotionality, and increased risk taking behaviors. Environmental enrichment (EE) provides a way to manipulate sensory, motor, and social experiences through interaction with same sex conspecifics in a setting often containing a variety of objects, ramps, and platforms. In this study, experimental groups included adolescent rats with a history of enrichment or not between postnatal day (PND) 25 and 48, and with a final enrichment exposure or not prior to sacrifice on PND 49. Brain tissue was processed to visualize c-FOS expression, and alternate Nissl sections were stained with thionin to discern neuron densities. The lateral amygdala (LA) showed a 24% greater density of neurons with a history of enrichment compared to non enriched rats (p< 0.001) suggesting periodic enrichment may spare neurons in LA. Rats with a history of EE displayed decreases in c-FOS+ neurons in LA -52%, posterior basolateral amygdala (pBLA) -33%, and central amygdala (CeA) -32% (all p< 0.05), with no significant difference in anterior basolateral amygdala (aBLA). The data suggests that rats may become accustomed to periodic EE exposure, which can explain less neural activation in amygdala of rats with an enrichment history.