The effects of noradrenaline and corticosterone on dendritic signal processing in cortical pyramidal cells of the rat hippocampus

Abstract

The ability of neurons to encode information and communicate with each other is vital for the normal functioning of our brain and body. The large pyramidal cells of the hippocampus have been of particular interest, due to the well-known role of the hippocampus in learning and memory, as well as epilepsy and stress. During a stressful event, noradrenaline and corticosterone are released. They act as neuromodulators, influencing signal processing and synaptic plasticity. The actions of these two neuromodulators have previously been studied separately, but not much is known about their interactions. The overall goal of this study was to investigate how noradrenaline and corticosterone influence and modulate dendritic signal processing in CA1 pyramidal cells of the hippocampus. It has become clear that the dendrites of neurons actively participate in signal processing, instead of just being passive conductors. The main aim of the study was to examine if corticosterone modulates the effect of noradrenaline on signaling processing. Additionally, the influence of these modulators of different ion channels that regulate postsynaptic potentials and slow afterhyperpolarizations were investigated, as these have been shown to influence synaptic plasticity. Using the whole-cell patch clamp technique, brain slices containing CA1 pyramidal cells from the hippocampus of rats were examined. Half the slices were incubated in 100 nM corticosterone 1 h prior to recording, the other half were used as controls. Recordings were made using specially constructed protocols. Corticosterone was not found to significantly modulate the effect of noradrenaline. The effects of noradrenaline on postsynaptic potentials, slow afterhyperpolarization, sag and input resistance all remained largely the same in the presence of corticosterone. In conclusion, corticosterone did not significantly modulate the effect of noradrenaline on the electrophysiological parameters studied in CA1 pyramidal cells in the rat hippocampus.