S. Roder et J. Ciriello, COLLATERAL AXONAL PROJECTIONS TO LIMBIC STRUCTURES FROM VENTROLATERALMEDULLARY A1 NORADRENERGIC NEURONS, Brain research, 638(1-2), 1994, pp. 182-188
Experiments were done to investigate whether catecholaminergic neurons
within the ventrolateral medulla (VLM) send collateral axonal project
ions to the central nucleus of the amygdala (ACe) and the bed nucleus
of the stria terminalis (BST). Unilateral microinjections of the fluor
escent retrograde tracers fluorogold (FG) or rhodamine labelled latex
micro-beads (Rd) were made into either ACe or BST in the rat. Brainste
m sections were then processed immunohistochemically for the identific
ation of cell bodies containing the catecholamine biosynthetic enzymes
tyrosine hydroxylase, dopamine beta-hydroxylase (DBH) or phenylethano
lamine-N-methyltransferase (PNMT). Retrogradely labelled cell bodies p
rojecting to either ACe or BST were found throughout the rostrocaudal
extent of VLM, bilaterally. Approximately 44% of these retrogradely la
belled neurons were found to contain both retrograde tracers. In addit
ion, approximately 91% of the VLM neurons that send collateral axonal
projections to ACe and BST were also immunoreactive to DBH. None were
found to contain PNMT immunoreactivity. These results demonstrate that
noradrenergic neurons of the Al cell group in VLM innervate ACe and B
ST via collateral axonal projections and suggest that these VLM neuron
s may be directly involved in relaying cardiovascular afferent and/or
visceral afferent information directly to these limbic structures.