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Abstract
Immunohistochemical detection of the immediate-early gene c-fos was used to determine
the pattern of neuronal activity in the rat brain after exposure to water-avoidance
stress known to stimulate fecal output in rats. Avoidance to water for 1 h by standing
on a small platform increases pellet output and induces numerous Fos-positive cells
in the parvocellular part of the paraventricular nucleus of the hypothalamus (PVN),
locus coeruleus (LC) and, to a lesser extent, in the bed nucleus of the stria terminalis,
lateral septum, dorsal raphe nucleus and A5 and A1 noradrenergic neurons. The corticotropin-releasing
factor (CRF) antagonist, alpha-helical CRF9-41 (50 micrograms i.c.v.) reduced water-avoidance
stress-induced c-fos expression mainly in the PVN and the LC (44 and 60%, respectively)
and decreased by 60% the stimulated fecal output. These data indicate that water-avoidance
stress activates PVN and LC neurons through CRF pathways which contribute to the stimulation
of colonic motor function.