Locus coeruleus and beta-adrenoreceptor-mediated regulation of synaptic plasticity and learning in the hippocampus

Abstract

Event Abstract Back to Event Locus coeruleus and beta-adrenoreceptor-mediated regulation of synaptic plasticity and learning in the hippocampus Denise Manahan-Vaughan1* 1 Ruhr University, Department of Experimental Neurophysiology, Germany Spatial memory formation is believed to occur by means of synaptic information processing, in the form of persistent strengthening and weakening of synapses, within the hippocampus. Long-term potentiation (LTP) and long-term depression (LTD) that last for hours, days and weeks are favoured candidate mechanisms that underlie long-term memory. The hippocampus receives a vast amount of sensory information, which must be filtered, prioritised and appropriately processed into information that is irrelevant, or relevant for storage in the form of short- or long-term memories. Our recent data suggest that the locus coeruleus may be particularly important in providing the saliency signal required to promote hippocampal encoding of relevant information through changes in synaptic strength. Coupling of hippocampal stimulation, that normally does not elicit changes in synaptic strength, with activation of the locus coeruleus, thus results in LTD at CA1 Stratum radiatum synapses in freely behaving adult rats [1]. Microdialysis revealed that locus coeruleus stimulation resulted in elevations of noradrenalin in the hippocampus. Application of a ß-adrenergic receptor antagonist prevented the expression of CA1 LTD following locus coeruleus stimulation. We additionally found that learning of a spatial task was enhanced by locus coeruleus stimulation, and that effects were also prevented by application of a ß-adrenergic receptor antagonist (Lemon et al, 2009).Independently of locus coeruleus stimulation, we found very pronounced effects of ß-adrenergic receptor antagonism effects on learning –facilitated plasticity in the hippocampus. Exploration of a novel environment facilitated LTP in the CA1 region, whereas exploration of novel spatial object constellations facilitated LTD [2]. Both phenomena were prevented by application of an antagonist of ß-adrenergic receptors Our results demonstrate that the locus coeruleus plays a key role in the induction of hippocampal LTD and in promoting the encoding of spatial information. This locus coeruleus -hippocampal interaction may reflect a means by which salient information is distinguished for subsequent synaptic processing. The ß-adrenergic receptor plays a critical role in mediated these, and other plasticity-related information encoding events in the hippocampus.