Pontospinal noradrenergic (NA) neurons are believed to play a role in the descending control of nociception and stimulation of the locus coeruleus (LC) can produce an antinociceptive effect at a spinal level through α2 adrenoceptors. However these experimental approaches employed local electrical stimulation of the LC which introduces potential confounds and it is not known whether these effects are mediated by postsynaptic actions of NA. We aimed to use selective, optoactivation of the LC to examine its effect on the excitability of lumbar dorsal horn (DH) neurones using patch clamp recording in vivo. Rats (160g, n=8) were anaesthetised for recovery surgery with ketamine (50mg/kg) and medetomidine (300µg/kg) i.p. for stereotactic viral vector injection to the right LC. A lentiviral vector expressing ChR2 under the control of the PRS promoter was injected into the LC (300nl/site x 3) and a guide cannula was implanted. Four weeks later the animals were anaesthetised with urethane (1.5g/kg, i.p.) and a 200µm diameter optical fibre was placed above the LC for optoactivation (470nm, 10-30mW). Whole-cell recordings were made from DH neurons of the L3 spinal cord segment. Cells were characterised as being either nociresponsive – high threshold (HT), low threshold (LT) or wide dynamic range (WDR) by responses to pinch or brush stimulation. Data are mean±SEM or median[IQR]. Recordings were obtained from 70 DH neurons (Vm-64.8±0.9mV, n=53, at depths from the surface of 230 [166-300] µm) of which 18 were identified as HT neurons of 57 tested. LC stimulation evoked changes in excitability with latency from stimulus onset of 15s [11-22.5] and lasting 45s [30-100] (n=19). LC activation excited 41%, inhibited 25%, had biphasic actions 8% and was without effect in 25% of DH neurons. The change in excitability was mediated by postsynaptic membrane polarisations (32%), changes in synaptic activity (23%) or both (34%). A similar picture was seen in HT cells with 5/17 inhibited and 8/17 excited with both membrane polarisations and changes in synaptic input. These actions could significantly alter the behaviour of the spinal neurons either leading to spike discharge or attenuating their synaptic inputs. Post-hoc histology confirmed successful vector transduction of the LC in all cases, with evidence of expression of ChR2-mCherry in DBH containing fibres in the spinal cord. These findings show that LC has multiple actions on sensory neurons in the DH. Far from observing a uniform inhibitory action (even on HT neurons) we were able to observe both pre and post-synaptic actions that were of both polarities. There is specificity of action of the LC at a spinal level and its engagement exerts bidirectional effects on sensory circuit excitability.