S. Kollackwalker et al., SOCIAL STRESS IN HAMSTERS - DEFEAT ACTIVATES SPECIFIC NEUROCIRCUITS WITHIN THE BRAIN, The Journal of neuroscience, 17(22), 1997, pp. 8842-8855
During an agonistic encounter, subordinate male hamsters display defen
sive and submissive postures and show increased secretion of glucocort
icoids, whereas dominant males do not. To determine whether specific n
euronal pathways are activated during the behavioral and neuroendocrin
e responses of subordinate males, expression of c-fos mRNA within the
brains of subordinate males was compared with the pattern in dominant
males after fighting. After 1 week of handling, pairs of hamsters were
either swapped between cages (handled control males), or were allowed
to interact for 30 min [dominant (DOM) males and subordinate (SUB) ma
les]. A second group of control animals that received no handling or s
ocial stimulation (unhandled control males) were also included. After
testing, all animals were killed by decapitation, their brains were re
moved for c-fos in situ hybridization, and trunk blood was collected f
or analysis of plasma cortisol and corticosterone levels. Exposure of
males to their partner's cage for 30 min resulted in increased express
ion of c-fos mRNA in multiple brain regions. In addition, fighting inc
reased c-fos expression in the medial amygdaloid nucleus of both DOM a
nd SUB males as well as having more selective effects. In DOM males, c
-fos expression was elevated within the supraoptic nucleus of the hypo
thalamus. In SUB males, c-fos expression increased within a multitude
of brain areas, including cingulate cortex, lateral septum, bed nucleu
s of the stria terminalis, medial preoptic area, several hypothalamic
nuclei, central amygdaloid nucleus, amygdalohippocampal area, dorsal p
eriaqueductal gray, dorsal raphe, cuneiform nucleus, and locus coerule
us. These findings are discussed in relation to neurocircuits associat
ed with behavioral arousal and stress.