Mm. Riccio et al., INTERGANGLIONIC SEGREGATION OF DISTINCT VAGAL AFFERENT FIBER PHENOTYPES IN GUINEA-PIG AIRWAYS, Journal of physiology, 496(2), 1996, pp. 521-530
1. The present study addressed the hypothesis that jugular and nodose
vagal ganglia contain the somata of functionally and anatomically dist
inct airway afferent fibres. 2. Anatomical investigations were perform
ed by injecting guinea-pig airways with the neuronal tracer Fast Blue.
The animals were killed 7 days later, and the ganglia were removed an
d immunostained with antisera against substance P (SP) and neurofilame
nt protein (NF). In the nodose ganglion, NF-immunoreactive neurones ac
counted for about 98% of the Fast Blue-labelled cells while in the jug
ular ganglion they accounted for approximately 49%. SP and NF immunore
activity was never (n = 100) observed in the same cell suggesting that
the antisera labelled distinct populations. 3. Electrophysiological i
nvestigations were performed using an in vitro guinea-pig tracheal and
bronchial preparation with intact afferent vagal pathways, including
nodose and jugular ganglia. Action potentials arriving from single air
way afferent nerve endings were monitored extracellularly using a glas
s microelectrode positioned near neuronal cell bodies in either gangli
on. 4. The nodose ganglion contained the somata of mainly fast-conduct
ing tracheal A delta fibres whereas the jugular ganglion contained equ
al numbers of C fibre and A delta fibre tracheal afferent somata. The
nodose A delta neurones adapted rapidly to mechanical stimulation, had
relatively low mechanical thresholds, were not activated by capsaicin
and adapted rapidly to a hyperosmotic stimulus. By contrast, jugular
A delta and C fibres adapted slowly to mechanical stimulation, were of
ten activated by capsaicin, had higher mechanical thresholds and displ
ayed a slow adaptation to a hyperosmotic stimulus. 5. The anatomical,
physiological and pharmacological data provide evidence to support the
contention that the vagal ganglionic source of the fibre supplying th
e airways ultimately dictates its neurochemical and physiological phen
otype.