Rk. Kanter et al., COMPARISON OF NEURONS IN RAT MEDULLA-OBLONGATA WITH FOS IMMUNOREACTIVITY EVOKED BY SEIZURES, CHEMORECEPTOR, OR BARORECEPTOR STIMULATION, Neuroscience, 73(3), 1996, pp. 807-816
Neurons in rat medulla oblongata with Fos immunoreactivity as a marker
of synaptic excitation evoked by pentylenetetrazole-induced seizures
were compared with cell populations activated by the stimulation of ch
emoreceptor and baroreceptor afferent pathways. Chemoreceptors were st
imulated by placing rats in a hypoxic gas mixture (7% oxygen) for 2 h.
Baroreceptors were activated by phenylephrine-induced hypertension. S
eizures and hypoxia induced Fos immunoreactivity in neurons with simil
ar anatomical distributions in the nucleus tractus solitarius, dorsal
motor nucleus of the vagus, and ventrolateral medulla. Hypertension wa
s associated with Fos immunoreactivity in an overlapping anatomical di
stribution compared to seizures and hypoxia, but in a more restricted
pattern. A similar proportion of catecholaminergic cells of medulla ob
longata (cells immunoreactive for catecholamine synthetic enzymes, tyr
osine hydroxylase or phenylethanolamine-N-methyltransferase) had Fos i
mmunostaining after seizures and hypoxia (P > 0.05), while significant
ly fewer were activated by hypertension (P < 0.05). The majority of ty
rosine hydroxylase-immunoreactive cells in caudal ventrolateral medull
a were activated by both seizures and hypoxia (mean per cents, 79 and
67%, respectively). Since cell populations activated by seizures and h
ypoxia are indistinguishable, and a majority of tyrosine hydroxylase-r
eactive cells in caudal ventrolateral medulla are independently activa
ted by each stimulus, it may be inferred that some impulses originatin
g from seizures and chemoreceptor afferent pathways converge to a comm
on set of neurons. These observations identify neurons in rat medulla
oblongata which may mediate the impact of seizures on central processi
ng of chemoreceptor afferent activity. Copyright (C) 1996 IBRO. Publis
hed by Elsevier Science Ltd.