Persistent pain responses in inflammation and corticosterone levels in juvenile rats born to adrenalectomized dams
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Studies in juvenile (Wistar) rats born to adrenalectomized dams (surgery performed 3–4 weeks before mating) addressed the intensity of behavioral pain responses (numbers of flexion + shaking patterns and durations of licking patterns) induced by foci of inflammation in the formalin test and plasma corticosterone levels on the background of the pain response. Maternal adrenalectomy had no effect on basal corticosterone levels or measures of the intensity of the pain response. In conditions of persistent pain (25 min after injection of formalin), corticosterone levels significantly (p < 0.05) increased in the offspring of both intact and operated dams. Females born to adrenalectomized dams, as compared with females from shamoperated dams, showed higher (p = 0.008) hormone levels in response to persistent pain. There were no differences in measures of the pain responses of the female offspring of adrenalectomized and sham-operated dams. There were no gender differences in measures of the pain response and hormone levels. Thus, pain evoked by acute foci of inflammation in the formalin test activated the hypothalamo-hypophysealadrenal system in 25-day-old rats, though the corticosterone released did not decrease pain intensity, which is consistent with data obtained from the offspring of adrenalectomized dams.
KEY WORDSpain formalin test ontogenesis corticosterone adrenalectomy rats
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