This proposal is to study the role of a specific neural pathway in the spinal cord and medulla of the brainstem in the control of the sympathetic nervous system. The uniqueness of this proposal is that the PI can identify a specific neural pathway by two chemical identifiers. Some pathways contain serotonin and some contain thyrotropin releasing hormone (TRH) but only one pathway contains both and it is by the combined use of these transmitters that the pathway can be recognized and defined. The study should add greatly to the accuracy of our understanding of brain control of the sympathetic nervous system.