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Attenuated neuroendocrine responses to emotional and physical stressors in pregnant rats involve adenohypophysial changes.
J Physiol 1998; 508 (Pt 1):289-300JP

Abstract

1. The responsiveness of the rat hypothalamo-pituitary-adrenal (HPA) axis and hypothalamo-neurohypophysial system (HNS) to emotional (elevated plus-maze) and physical (forced swimming) stressors and to administration of synthetic corticotrophin-releasing hormone (CRH) was investigated during pregnancy and lactation. In addition to pregnancy-related adaptations at the adenohypophysial level, behavioural responses accompanying the neuroendocrine changes were studied. 2. Whereas basal (a.m.) plasma corticosterone, but not corticotrophin (adrenocorticotrophic hormone; ACTH), levels were increased on the last day (i.e. on day 22) of pregnancy, the stress-induced rise in both plasma hormone concentrations was increasingly attenuated with the progression of pregnancy beginning on day 15 and reaching a minimum on day 21 compared with virgin control rats. A similar attenuation of responses to both emotional and physical stressors was found in lactating rats. 3. Although the basal plasma oxytocin concentration was elevated in late pregnancy, the stress-induced rise in oxytocin secretion was slightly lower in day 21 pregnant rats. In contrast to vasopressin, oxytocin secretion was increased by forced swimming in virgin and early pregnant rats indicating a differential stress response of these neurohypophysial hormones. 4. The blunted HPA response to stressful stimuli is partly due to alterations at the level of corticotrophs in the adenohypophysis, as ACTH secretion in response to CRH in vivo (40 ng kg-1, i.v.) was reduced with the progression of pregnancy and during lactation. In vitro measurement of cAMP levels in pituitary segments demonstrated reduced basal levels of cAMP and a lower increase after CRH stimulation (10 nM, 10 min) in day 21 pregnant compared with virgin rats, further indicating reduced corticotroph responsiveness to CRH in pregnancy. 5. The reduced pituitary response to CRH in late pregnancy is likely to be a consequence of a reduction in CRH receptor binding as revealed by receptor autoradiography. [125I] CRH binding in the anterior pituitary was significantly reduced in day 11, 17 and 22 pregnant rats compared with virgin controls. 6. Anxiety-related behaviour of the animals as revealed by the time on and entries into the open arms of the elevated plus-maze was different between virgin and pregnant rats with decreased number of entries indicating increased anxiety with the progression of pregnancy (except on pregnancy day 18). The emotional behaviour, however, was not correlated with the neuroendocrine responses. 7. The results indicate that the reduced response of the HPA axis to stressors described previously during lactation is already manifested around day 15 of pregnancy in the rat and involves physiological adaptations at the adenohypophysial level. However, alterations in stressor perception at higher brain levels with the progression of pregnancy may also be involved.

Authors+Show Affiliations

Max Planck Institute of Psychiatry, Munich, Germany. INEU@MPIPSYKL.MPG.DENo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9490853

Citation

Neumann, I D., et al. "Attenuated Neuroendocrine Responses to Emotional and Physical Stressors in Pregnant Rats Involve Adenohypophysial Changes." The Journal of Physiology, vol. 508 (Pt 1), 1998, pp. 289-300.
Neumann ID, Johnstone HA, Hatzinger M, et al. Attenuated neuroendocrine responses to emotional and physical stressors in pregnant rats involve adenohypophysial changes. J Physiol (Lond). 1998;508 (Pt 1):289-300.
Neumann, I. D., Johnstone, H. A., Hatzinger, M., Liebsch, G., Shipston, M., Russell, J. A., ... Douglas, A. J. (1998). Attenuated neuroendocrine responses to emotional and physical stressors in pregnant rats involve adenohypophysial changes. The Journal of Physiology, 508 (Pt 1), pp. 289-300.
Neumann ID, et al. Attenuated Neuroendocrine Responses to Emotional and Physical Stressors in Pregnant Rats Involve Adenohypophysial Changes. J Physiol (Lond). 1998 Apr 1;508 (Pt 1):289-300. PubMed PMID: 9490853.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Attenuated neuroendocrine responses to emotional and physical stressors in pregnant rats involve adenohypophysial changes. AU - Neumann,I D, AU - Johnstone,H A, AU - Hatzinger,M, AU - Liebsch,G, AU - Shipston,M, AU - Russell,J A, AU - Landgraf,R, AU - Douglas,A J, PY - 1998/6/6/pubmed PY - 1998/6/6/medline PY - 1998/6/6/entrez SP - 289 EP - 300 JF - The Journal of physiology JO - J. Physiol. (Lond.) VL - 508 (Pt 1) N2 - 1. The responsiveness of the rat hypothalamo-pituitary-adrenal (HPA) axis and hypothalamo-neurohypophysial system (HNS) to emotional (elevated plus-maze) and physical (forced swimming) stressors and to administration of synthetic corticotrophin-releasing hormone (CRH) was investigated during pregnancy and lactation. In addition to pregnancy-related adaptations at the adenohypophysial level, behavioural responses accompanying the neuroendocrine changes were studied. 2. Whereas basal (a.m.) plasma corticosterone, but not corticotrophin (adrenocorticotrophic hormone; ACTH), levels were increased on the last day (i.e. on day 22) of pregnancy, the stress-induced rise in both plasma hormone concentrations was increasingly attenuated with the progression of pregnancy beginning on day 15 and reaching a minimum on day 21 compared with virgin control rats. A similar attenuation of responses to both emotional and physical stressors was found in lactating rats. 3. Although the basal plasma oxytocin concentration was elevated in late pregnancy, the stress-induced rise in oxytocin secretion was slightly lower in day 21 pregnant rats. In contrast to vasopressin, oxytocin secretion was increased by forced swimming in virgin and early pregnant rats indicating a differential stress response of these neurohypophysial hormones. 4. The blunted HPA response to stressful stimuli is partly due to alterations at the level of corticotrophs in the adenohypophysis, as ACTH secretion in response to CRH in vivo (40 ng kg-1, i.v.) was reduced with the progression of pregnancy and during lactation. In vitro measurement of cAMP levels in pituitary segments demonstrated reduced basal levels of cAMP and a lower increase after CRH stimulation (10 nM, 10 min) in day 21 pregnant compared with virgin rats, further indicating reduced corticotroph responsiveness to CRH in pregnancy. 5. The reduced pituitary response to CRH in late pregnancy is likely to be a consequence of a reduction in CRH receptor binding as revealed by receptor autoradiography. [125I] CRH binding in the anterior pituitary was significantly reduced in day 11, 17 and 22 pregnant rats compared with virgin controls. 6. Anxiety-related behaviour of the animals as revealed by the time on and entries into the open arms of the elevated plus-maze was different between virgin and pregnant rats with decreased number of entries indicating increased anxiety with the progression of pregnancy (except on pregnancy day 18). The emotional behaviour, however, was not correlated with the neuroendocrine responses. 7. The results indicate that the reduced response of the HPA axis to stressors described previously during lactation is already manifested around day 15 of pregnancy in the rat and involves physiological adaptations at the adenohypophysial level. However, alterations in stressor perception at higher brain levels with the progression of pregnancy may also be involved. SN - 0022-3751 UR - https://www.unboundmedicine.com/medline/citation/9490853/Attenuated_neuroendocrine_responses_to_emotional_and_physical_stressors_in_pregnant_rats_involve_adenohypophysial_changes_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0022-3751&date=1998&volume=508&spage=289 DB - PRIME DP - Unbound Medicine ER -