European Journal of Neuroscience · 2001 · 514 citations · 36 references
Life SciencesNeurobiologyNeuroscienceBehavioral NeuroscienceNeuroendocrinologyStress PhysiologyNeuroendocrine ResponsesPsychological StressStress NeuroscienceStress Response GenesStress ResponsesStress-induced Gene ExpressionEndocrine Stress ResponseNeuroendocrine Stress PathwaysNeuroendocrine Stress ResponseNoradrenergic NeurotransmissionStress Axis PhysiologyStress HormonesStress-induced Neuroendocrine Responses
The brain is thought to categorize stressors, using distinct neural pathways that vary with the assigned category, a hypothesis suggested by early immediate‑early gene studies but limited by methodological differences. This study aimed to determine whether different stressors elicit category‑specific patterns of neuronal activation in the rat brain. Researchers employed c‑fos immunolabelling to map neuronal activity induced by haemorrhage, immune challenge, noise, restraint, and forced swim in the rat brain. All stressors activated the HPA axis similarly, yet haemorrhage and immune challenge recruited central amygdala neurons and rostral A1/A2 noradrenergic cells, whereas noise, restraint, and forced swim preferentially activated medial amygdala neurons and more caudal noradrenergic cells, supporting the existence of distinct physical and psychological stressor categories whose neural footprints can identify the assigned category.
Abstract It has been hypothesized that the brain categorizes stressors and utilizes neural response pathways that vary in accordance with the assigned category. If this is true, stressors should elicit patterns of neuronal activation within the brain that are category‐specific. Data from previous immediate–early gene expression mapping studies have hinted that this is the case, but interstudy differences in methodology render conclusions tenuous. In the present study, immunolabelling for the expression of c‐ fos was used as a marker of neuronal activity elicited in the rat brain by haemorrhage, immune challenge, noise, restraint and forced swim. All stressors elicited c‐ fos expression in 25–30% of hypothalamic paraventricular nucleus corticotrophin‐releasing‐factor cells, suggesting that these stimuli were of comparable strength, at least with regard to their ability to activate the hypothalamic–pituitary–adrenal axis. In the amygdala, haemorrhage and immune challenge both elicited c‐ fos expression in a large number of neurons in the central nucleus of the amygdala, whereas noise, restraint and forced swim primarily elicited recruitment of cells within the medial nucleus of the amygdala. In the medulla, all stressors recruited similar numbers of noradrenergic (A1 and A2) and adrenergic (C1 and C2) cells. However, haemorrhage and immune challenge elicited c‐ fos expression in subpopulations of A1 and A2 noradrenergic cells that were significantly more rostral than those recruited by noise, restraint or forced swim. The present data support the suggestion that the brain recognizes at least two major categories of stressor, which we have referred to as ‘physical’ and ‘psychological’. Moreover, the present data suggest that the neural activation footprint that is left in the brain by stressors can be used to determine the category to which they have been assigned by the brain.
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