The destination of the sympathetic outflow which arises from sympathetic preganglionic neurons located in the thoraco-lumbar spinal cord is a myriad of target organs that include the vasculature, the adrenal gland, the viscera and brown adipose tissue. Much work has been directed at determining what areas of the brain influence which of these functional outflows and how this is regulated. For example, we have demonstrated that somatostatin inhibits, by way of somatostatin 2A receptors, a select population of neurons in the rostral ventrolateral medulla that regulate vasomotor tone by way of a fast conducting spinal pathway (1,2). We have combined a functional approach with anatomical analysis to investigate the neurochemicals used to control these neuronal pathways. A wide range of neurotransmitters/neuromodulators are found in presympathetic pathways that control sympathetic preganglionic neurons and in the preganglionic neurons themselves. These neurochemicals include amino acids, short lived gases and peptides. This presentation will discuss the role of inhibitory neuropeptides in the control of the sympathetic outflows named above. We have identified how specific outflows are influenced by a range of inhibitory neuropeptides in the spinal cord. The use of specific physiological stressors has permitted the identification of the neurons activated and retrograde tracing techniques allow target organ destination of neurons to be identified. Using such approaches we have defined the neurochemical codes for neurons activated by glucoprivic and hypotensive stimuli. The role of neuropeptides in particular and the colocalisation of multiple neurotransmitters in general will also be addressed.