The Locus Coeruleus (LC) is the primary central nervous system source of noradrenaline, with roles in various arousal related brain-states and behaviours. Within the LC, noradrenaline has a potent feedback inhibitory effect, silencing spontaneous activity and regulating phasic bursts of spiking. In this work, we utilised a noradrenergic-specific viral vector (CAV-PRS-ChR2, Li et al 2016) to transfect a proportion of LC cells with the optogenetic activator ChannelRhodopsin. Subsequently we were able to optogenetically drive LC cells in a temporally precise manner in vitro, producing post-excitatory inhibition in transduced cells, and inhibition of spontaneous activity in non-transduced cells. Congruent with previous investigations, inhibition was due to an outward current sensitive to noradrenaline reuptake, mediated by alpha-2-adrenoceptors ( α2Rs ), and occurring over a timecourse of hundreds of milliseconds (time to peak = 561ms +/- 261ms S.E.M). This current showed inward-rectifying properties, and was blocked by Caesium, consistent with G-protein-coupled inward-rectifying Potassium (GIRK) channels. The current amplitude was strongly modulated by the frequency of optogenetic stimulus, suggesting dependence on presynaptic Calcium concentration. Additionally, the inhibitory current was still evident in the presence of TTX producing sodium spike blockade, suggesting LC neuron calcium action potentials are sufficient to drive noradrenaline release. To investigate this hypothesis, a computational model was constructed, based on existing Hodgkin-Huxley formulations of LC neurons (Alvarez et al, 2002), augmented with Calcium-dependent inhibitory transients modelling noradrenaline release, binding to α2Rs, and activating GIRK channels. This was sufficient to replicate both the basic dynamics of opto-activated inhibition seen in electrophysiological recordings, and the relationship between optogenetic stimulus frequency and evoked current amplitude. Together, these investigations contribute to understanding noradrenergic inhibition in the LC as both auto-and lateral inhibitory in nature, and fit into an emerging view of the LC as a heterogeneous, modular system (Chandler et al, 2020).