I. Kita et al., ADRENERGIC CELL GROUP IN ROSTRAL VENTROLATERAL MEDULLA OF CAT - ITS CORRELATION WITH CENTRAL CHEMORECEPTORS, Neuroscience research, 20(3), 1994, pp. 265-274
We have proposed a hypothesis that secondary neurons mediating central
respiratory chemoreception are not restricted to the medullary superf
icial layer. This idea was further examined in the present physiologic
al and morphological studies. We identified the 'S' area, i.e. the med
ullary surface area where cold blockade produced apnea, in anesthetize
d, spontaneously breathing cat. We then evaluated how the apnea was mo
dified by injection of CO2-saturated saline into the vertebral-basilar
artery. The CO2 injection caused immediate reappearance of respirator
y rhythm, although intensity of inspiratory activity was smaller than
in the control. This incomplete recovery suggests that the responsive
structure extends deeply below the surface. The extent of the cell gro
up underlying the 'S' area was evaluated by morphological study. Medul
lary transverse sections including the 'S' area were treated with thre
e distinct antisera against phenylethanolamine N-methyltransferase (PN
MT), dopamine-beta-hydroxylase (DBH), and 5-hydroxytryptamine (5-HT).
The PNMT-labelled cell group was found to exactly underlie the 'S' are
a, although the DBH-and the 5-HT-labelled cell groups did not show clo
se topographic correlation with the 'S' area. PNMT cells were located
in the region ventral to retrofacial nucleus within 0.5-1.5 mm depth b
eneath the surface. These results suggest that adrenergic cells in the
rostral ventrolateral medulla are important candidates for secondary
neurons mediating central respiratory chemoreception.