Repeated restraint stress exerts different impact on structure of neurons in the lateral and basal nuclei of the amygdala

Chronic stress exacerbates and can induce symptoms of depression and anxiety disorders. Chronic stress causes amygdala hyperactivity, which may contribute to these detrimental effects. One potential mechanism for amygdala hyperactivity is an increase of excitatory drive after stress. Excitatory inputs to the amygdala predominantly synapse upon dendritic spines, and repeated stress has been demonstrated to increase dendritic spines in the basolateral amygdala (BLA). However, the BLA is comprised of several nuclei, including the lateral nucleus (LAT) and the basal nucleus (BA), which exert functionally distinct roles in amygdala-dependent behaviors. Furthermore, while an increase of dendritic spines can impart significant functional ramifications, a shift of spine distribution can also exert significant impact. However, differences in the effects of repeated stress on LAT and BA have not been examined, nor differential effects on spine distribution. This study examined the effects of repeated restraint stress on dendritic structure of principal neurons from the LAT and BA in Golgi-stained tissue. This study found that repeated stress increased spine number in LAT and BA, but in very distinct patterns, with proximal increases in LAT neurons and non-proximal increases in BA neurons. Furthermore, repeated stress increased dendritic length in the BA, but not the LAT, leading to a global change of spine density in BA, but a focal change in LAT. These distinct effects of repeated stress in the LAT and BA may exert significant functional effects on fear behavior, and may underlie differences in the effects of repeated stress on acquisition, contextual modulation and extinction of fear behavior.