Noradrenaline and Beta-Adrenoceptor Agonists Increase Activity of Voltage-Dependent Calcium Channels in Hippocampal Neurons

摘要

The predominance of unconventional transmitter release sites at noradrenaline containing synapses and the diffuse projections of noradrenaline (NA) containing fibres originating in locus coeruleus have led to speculation that NA may act as a neuromodular in the central nervous system. Evidence suggests that it has a modulatory role in the plasticity of the developing nervous system in controlling behavioural states of an organism, and in learning and memory. Recently, Hopkins and Johnston demonstrated that NA enhances the magnitude, duration, and probability of induction of long term potentiation (LTP) at mossy fibre synapses in the hippocampal formation, and LTP is widely believed to be a cellular substrate for aspects of memory. To investigate the membrane effects of NA on central neurones, the authors used a newly developed preparation in which patch clamp techniques can be applied to exposed adult cortical neurones. The authors report here that NA produces an enhancement in the activity of voltage dependent calcium channels in granule cells of the hippocampal dentate gyrus. This action of NA appears to be mediated by adrenoceptors and can be mimicked by cyclic AMP.