Effect of development of habituation to restraint stress on hypothalamic noradrenaline release and adrenocorticotropin secretion

S. Terrazzino, C. Perego, M. G. De Simoni

Research output: Contribution to journalArticle

Abstract

The effect of repeated stress has been studied on noradrenaline release in the hypothalamic paraventricular nucleus and on adrenocorticotropin levels. Rats were stressed by 20-min immobilization once a day for 5 days. On day 6 they were exposed to the same stress or to a different one (ether vapors for 2 min). Immobilization and ether stress increased noradrenaline release in naive rats (271 ± 43 and 197 ± 9%, respectively) and raised adrenocorticotropin levels, showing activation of the hypothalamus-pituitary axis. Repeated daily restraint did not modify basal noradrenaline or adrenocorticotropin levels. The further immobilization session on day 6 did not change noradrenaline levels at any observation time (20-120 min). The adrenocorticotropin response was still present, although significantly reduced. In repeatedly restrained rats, exposure to ether vapors induced a maximal increase in noradrenaline level similar to that observed in naive rats, although prolonged. In these rats the adrenocorticotropin response did not differ from that in acutely stressed rats. These results suggest that habituation may develop to a stressful stimulus leading to suppression of the hypothalamic noradrenergic response and that this phenomenon is stress specific. Moreover, modifications of noradrenaline release in the paraventricular nucleus are not solely responsible for the adrenocorticotropin response during stress, suggesting that other pathways and/or neurotransmitters are involved too.

Original languageEnglish
Pages (from-to)263-267
Number of pages5
JournalJournal of Neurochemistry
Volume65
Issue number1
Publication statusPublished - Jul 1995

Keywords

  • Adrenocorticotropin
  • Habituation
  • Hypothalamic paraventricular nucleus
  • Intracerebral microdialysis
  • Noradrenaline
  • Stress

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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