Differences in intrinsic amygdalar network features between animals of the high- vs. low-anxiety-related behavior (HAB, LAB) mouse model

Alterations in neuronal network excitability in the amygdala, a temporal lobe structure, are characteristic features of certain psychiatric illnesses, such as anxiety and depressive disorders. To potentially uncover changes in neuronal network features associated with abnormal anxiety, we performed experiments in a well-established animal model of extremes in trait anxiety, namely the high- vs. low-anxiety-related behaviour (HAB/LAB) mouse model. HAB mice exposed to an enriched environment (HAB-EE) and stressed LAB mice were also used in the present study. HAB-EE animals showed decreased anxiety compared to HAB controls, whereas stressed LAB animals showed an increase in anxiety levels compared to LAB controls. Anxiety levels were measured by means of the elevated plus maze. For our investigations, we employed classical electrophysiological techniques and voltage-sensitive dye imaging (VSDI) in acute amygdalar brain slices. Field potential recordings revealed that corticotropin-releasing hormone (CRH), a neuropeptide with anxiogenic properties, increases the excitability of the lateral/basolateral amygdalar network more pronounced in HAB than LAB animals. To examine whether neuronal activity propagation through the amygdala differs between HAB, HAB-EE, LAB, and stressed LAB mice, we used a quantitative VSDI approach. The results of these experiments clearly show that differences in anxiety levels strongly correlate with the effectiveness of evoked neuronal activity.