A ventromedullary relay involved in the hypothalamic and chemoreceptor activation of sympathetic postganglionic neurones to skeletal muscle, kidney and splanchnic area.

Bilateral application of glycine to the ventral surface of the medulla produces a profound hypotension during which sympathetic vasoconstrictor activity to splanchnic, renal and skeletal muscle vascular beds is reduced. The pattern of activation of sympathetic vasoconstrictor fibres to kidney and skeletal muscle, during carotid chemoreceptor activation and hypothalamic stimulation, is attenuated as tonic sympathetic activity diminishes. Functioning ventromedullary neurones are thus necessary for maintaining tonic sympathetic nerve activity, and for reflex and brain evoked patterns of sympathetic nerve activity, in the anaesthetized cat.