High-speed voltage-sensitive dye imaging reveals an enhancing effect of corticotropin-releasing hormone (CRH) on neuronal activity propagation through the hippocampal formation

Corticotropin-releasing hormone (CRH) is thought to play an important role in the development of stress-related psychiatric disorders such as depression and anxiety disorders. However, the knowledge about the actions of CRH at the neuronal network level is only scarce. Here, we examined whether CRH affects neuronal activity propagation through the hippocampal formation, a brain region which is likely to be involved in stress-related alterations of learning and memory. For this purpose, we applied high-speed voltage-sensitive dye imaging (VSDI) to a murine hippocampal brain slice preparation. The technique of VSDI allows to measure neuronal network activity with micrometer spatial resolution on millisecond time scales. We found a marked enhancing effect of bath-applied CRH (50 nM) on electrically evoked neuronal activity propagation from the dentate gyrus to the CA1 subfield. This effect was absent in conditional knockout mice selectively lacking the CRH-receptor type 1 (CRHR1) on glutamatergic neurons. The present study shows that CRH is capable of profoundly modulating activity flow through neuronal networks.