A combined immunocytochemical and retrograde tracing study of noradrenergic connections between the caudal medulla and bed nuclei of the stria terminalis

Region-specific noradrenergic inputs to the bed nuclei of the stria terminalis (BST) from the caudal medulla were studied using combined Fast Blue injections and tyrosine hydroxylase immunoreactivity (TH-ir). Injections into the rostral, dorsal, ventral and lateral BST resulted in predominantly ipsilateral retrograde labelling restricted to the mediodorsal and ventrolateral caudal medulla. Mediodorsal projecting neurones comprised the A2 TH-ir and a second non-aminergic group medial to A2. All ventrolateral retrogradely labelled neurones showed TH-ir and corresponded to A1. Injections into the caudal BST did not label the A2 and very few A1 neurones, indicating a paucity of noradrenergic inputs from this area of the medulla.