Transcutaneous vagal nerve stimulation (tVNS) is achieved via electrically stimulating the peripheral endings of the auricular branch of the vagus nerve (ABVN). In humans, tVNS can influence cardiovascular function by improving heart rate variability (HRV) and decreasing sympathetic nerve activity (Clancy et al., 2014). We sought to understand, in a rat model, whether similar effects were observed and the pathways underlying these effects. Rats (n=10) were anaesthetised with isoflurane, decerebrated and prepared for anaesthetic-free working heart-brainstem preparation as described (Paton, 1996). Applying 5 minutes of right tragus stimulation via an alligator clip (100 Hz, 1mA) immediately reduced sympathetic activity recorded from the thoracic sympathetic chain (baseline = 4.87 ± 0.51 AU vs stimulation = 4.01 ± 0.54 AU ; p < 0.05). The effects of sympathoinhibiton persisted for 5 minutes after cessation of stimulation. There was also a significant reduction in arterial pressure, starting at 2 minutes following the beginning of stimulation (T2) and persisting for 4 minutes after the stimulation stopped (T9) (Figure 1). These changes occurred without significantly affecting heart or respiratory rate. To study the central terminations of sensory afferent nerves from the auricular tragus, 7 Wistar rats (200-250g) of either sex were deeply anaesthetised. Animals were injected subcutaneously with cholera toxin subunit B (CTb) (5 μl, 5.3 mg/ml) into the tragus. Four days post injection animals were deeply anaesthetised with 80 mg/kg of intraperitoneal sodium pentobarbitone and perfused with 4% paraformaldehyde (PFA). Following overnight post-fixation the upper cervical spinal cord and lower brainstem were sectioned at 50 μm using a vibrating microtome and processed with CTb immunohistochemistry. Heavy central terminations from tragus injections were found in the dorsal horn of the upper cervical spinal cord covering laminae II and III. In the medulla, there was moderate terminal labelling in the cuneate fasciculus and paratrigeminal nucleus. There was little labelling in the nucleus tractus solitaries (NTS) which is a primary sensory afferent integration site that also received inputs from baroreceptors (Andresen & Mendelowitz, 1996). The identity of post-synaptic cells was then sought by immunostaining for ChAT, Calbindin, GAD67, NKR1 or Parvalbumin: CTB labelled close appositions were infrequently detected onto each cell type. TVNS in rats therefore induces a sympathoinhibition similar to that in humans. The pathways through which tVNS functions remains to be concluded, but limited labelling in the NTS indicates that this region is not the initial termination point for auricular afferents to exert their influence on sympathetic nerve activity.