Zj. Gieroba et Ww. Blessing, FOS-CONTAINING NEURONS IN MEDULLA AND PONS AFTER UNILATERAL STIMULATION OF THE AFFERENT ABDOMINAL VAGUS IN CONSCIOUS RABBITS, Neuroscience, 59(4), 1994, pp. 851-858
Vagal afferents originating in abdominal viscera initiate numerous cen
trally-mediated responses, including behavioural, cardiovascular and h
ormonal changes associated with satiety, and nausea and vomiting. The
present work was undertaken to map the pontomedullary distribution of
neurons expressing Fos immunoreactivity following unilateral electrica
l stimulation of abdominal vagal afferents in conscious unanaesthetize
d rabbits. After 2 h of stimulation of the anterior trunk of the abdom
inal vagus nerve (20 Hz, 0.5 mA, 0.5 ms duration, 4.5 min on, 0.5 min
off), Fos-positive neurons were found in the area postrema, the nucleu
s tractus solitarius, the spinal nucleus of the trigeminal nerve, the
caudal and the rostral ventrolateral medulla, the locus coeruleus, the
subcoeruleus and the lateral parabrachial nucleus. In all these regio
ns, more than 70% of Fos-containing neurons occurred on the ipsilatera
l side. In control animals only occasional Fos-immunoreactive neurons
were observed, usually very faintly labelled. Simultaneous staining fo
r both Fos and tyrosine hydroxylase revealed Fos immunoreactivity in c
atecholamine neurons, including A1, A2, C1, A5, subcoeruleus and locus
coeruleus (A6) groups. Our findings complement functional studies in
the rabbit, identifying Al neurons as part of the central pathway by w
hich afferent abdominal vagal stimulation increases plasma vasopressin
, and C1 neurons as part of the central pathway, whereby afferent abdo
minal vagal stimulation increases arterial pressure.