Sympathetic preganglionic neurones (SPNs) are the final common pathway for CNS inputs to influence sympathetic nervous outflow. It is well established that SPN activity is influenced by supraspinal regions. In addition, local interneurones are increasingly being recognised as likely important controllers of SPN behaviour. Recently, the central autonomic area (CAA) was shown to contain GABAergic, presympathetic interneurones (Deuchars et al., 2005). The CAA is innervated by many supraspinal projections (Krukoff et al., 1985). This work aimed to determine if GABAergic neurones in the CAA receive inputs from neurones in supraspinal regions related to sympathetic control. Descending inputs to the spinal cord were identified using immunohistochemistry for 5-hydroxytryptamine (5-HT) or tyrosine hydroxylase (TH). GABAergic neurones in the CAA were visualised using transgenic reporter mice (De Marchis et al., 2004) expressing GFP under control of the promoter for glutamate decarboxylase65 (GAD65), and in rat tissue stained immunohistochemically for GAD67. Animals were anaesthetised with an intraperitoneal injection of Sagatal (60mg/kg) and perfused transcardially with 4% paraformaldehyde in 0.1M phosphate buffer, pH 7.4. Thoracic spinal cord was removed and sectioned at 50µm on a vibratome. Sections were incubated in either sheep anti TH (1:100, Abcam) or rabbit anti-5HT (1:1000, US Biologicals) and mouse anti-GFP (1:1000, Invitrogen) at 4°C for 12-36hrs. Anti-GFP was visualised using a green fluorescing secondary antibody (Alexa⁴⁸⁸-conjugated donkey anti-mouse, Invitrogen) whilst descending inputs with either blue (Coumarin based TSA kit, Perkin Elmer) or red (Cy3-conjugated donkey anti-goat or Alexa⁵⁵⁵-conjugated donkey anti-rabbit, Jackson Immunoresearch and Invitrogen respectively). Both 5-HT and TH-containing-terminals were highly concentrated in the IML and immunoreactivity extended to the CAA, where terminals were visible in the vicinity of GFP cells. High power examination revealed 5-HT-containing terminals in a dense plexus in the CAA, where some of the terminals were closely apposed to GFP cell bodies and proximal dendrites. Confocal microscopy was used to quantify the fraction of CAA cells receiving close apposition by 5-HT-containing terminals, and the contact density of those cell body appositions. Of 24 cells examined, 23 (95%) received appositions ranging from 0.09 – 2.07 contacts per 100 µm² (1-11 appositions per cell body). Similar analysis is currently underway for TH-containing appositions. Thus we have identified that supraspinal inputs which directly influence SPNs may also influence GABAergic CAA interneurones, providing a possible indirect pathway for affecting sympathetic outflow.