Noradrenaline and β-adrenoceptor agonists increase activity of voltage-dependent calcium channels in hippocampal neurons

The predominance of unconventional transmitter release sites at noradrenaline-containing synapses and the diffuse projections of noradrenaline-containing fibres originating in locus coeruleus1 have led to speculation that noradrenaline may act as a neuromodu-lator2–6 in the central nervous system. Evidence suggests that it has a modulatory function in the plasticity of the developing nervous system7,8, in controlling behavioural states of an organism3–6, and in learning and memory9–11. Recently, Hopkins and Johnston12 demonstrated that noradrenaline 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 memory13,14. To investigate the membrane effects of noradrenaline on central neurons, we used a newly developed preparation in which patch-clamp techniques can be applied to exposed adult cortical neurons. We report here that noradrenaline produces an enhancement in the activity of voltage-dependent calcium channels in granule cells of the hippocampal dentate gyrus. This action appears to be mediated by β-adrenoceptors and can be mimicked by cyclic AMP.