Neurotransmitters involved in the central regulation of the cardiovascular system

Arterial blood pressure is maintained by the tonic vasomotor activity of sympathetic preganglionic neurons which are located in the intermediolateral cell column of the thoracic and lumbar spinal cord. Supraspinal inputs are critical in maintaining the activity of SPN. The medulla and pons have been recognized as essential for maintaining tonic sympathetic activity since the late 1800’s when experiments showed that transection of the brain stem caudal to the inferior colliculus failed to lower blood pressure. Transections more caudally produced increasingly greater falls in blood pressure. Reductions in blood pressure reached a maximum with transections at the level of the obex (see ref [1] for historical review). A major goal of central autonomic research has been to identify the descending neuronal pathways which project to SPN and to determine the neurotransmitters contained within these pathways (see ref [2–6] for review). Neuroanatomical and immunocytochemical techniques have been used to identify chemically specific pathways between areas thought to be important in central autonomic regulation. This information combined with experiments utilizing sophisticated electrophysiological and pharmacological analysis have begun to elucidate the role of these pathways in central autonomic regulation and to determine the functional significance of putative neurotransmitters contained within these pathways. This review describes recent developments which have had a major influence on our understanding of the central neurotransmitters involved in the regulation of sympathetic nerve discharge.