Sd. Stocker et al., CONNECTIONS OF THE CAUDAL VENTROLATERAL MEDULLARY RETICULAR-FORMATIONIN THE CAT BRAIN-STEM, Experimental Brain Research, 116(2), 1997, pp. 270-282
A region of the caudal ventrolateral medullary reticular formation (CV
LM) participates in baroreceptor, vestibulosympathetic, and somatosymp
athetic reflexes; the adjacent retroambigual area is involved in gener
ating respiratory-related activity and is essential for control of the
upper airway during vocalization. However, little is known about the
connections of the CVLM in the cat. In order to determine the location
s of terminations of CVLM neurons, the anterograde tracers Phaseolus v
ulgaris leucoagglutinin and tetramethylrhodamine dextran amine were in
jected into this region. These injections produced a dense concentrati
on of labeled axons throughout the lateral medullary reticular formati
on (lateral tegmental field), including the retrofacial nucleus and nu
cleus ambiguus, regions of the rostral ventrolateral medulla, the late
ral and ventrolateral aspects of the hypoglossal nucleus, nucleus inte
rcalatus, and the facial nucleus. A smaller number of labeled axons we
re located in the medial, lateral, and commissural subnuclei of nucleu
s tractus solitarius, the A5 region of the pontine reticular formation
, the ventral and medial portions of the spinal and motor trigeminal n
uclei, locus coeruleus, and the parabrachial nucleus. We confirmed the
projection from the CVLM to both the rostral ventrolateral medulla an
d lateral tegmental field using retrograde tracing. Injections of biot
inylated dextran amine or Fluorogold into these regions resulted in re
trogradely labeled cell bodies in the CVLM. However, the neurons proje
cting to the lateral tegmental field were located mainly dorsal to tho
se projecting to the rostral ventrolateral medulla, suggesting that th
ese neurons form two groups, possibly with different inputs. Injection
s of retrograde tracers into the lateral tegmental field and rostral v
entrolateral medulla also produced labeled cell bodies in other region
s, including the medial and inferior vestibular nuclei and nucleus sol
itarius. These data are consistent with the view that the CVLM of the
cat is a multifunctional area that regulates blood pressure, produces
vocalization, affects the shape of the oral cavity, and elicits contra
ction of particular facial muscles.