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Rhythmicity of beta-endorphinergic neuronal activity in the mediobasal hypothalamus during pregnancy in the rat.
Brain Res. 1999 Aug 07; 837(1-2):152-60.BR

Abstract

During the first half of gestation in the rat, prolactin (PRL) from the anterior pituitary gland exerts its luteotropic function on the ovary to stimulate progesterone secretion. During this period, beta-endorphin stimulates PRL secretion by regulation of dopaminergic neurons in the hypothalamus. During the second half, placental lactogens (PLs) take the place of PRL in maintenance of pregnancy, and initiate a negative feedback to suppress PRL secretion. However, the effect of PLs on beta-endorphinergic neurons is not known. The aim of this study was to examine the possibility that PLs suppress PRL secretion by inhibiting beta-endorphinergic neuronal activity. To accomplish this aim, we examined the changes in the neuronal activity of beta-endorphinergic neurons in the mediobasal hypothalamus, as measured by Fos immunoreactivity, after manipulating the levels of PRL and PLs during pregnancy. On day 4 of pregnancy, animals received either Rcho-1 cells in the lateral ventricle that secrete PLs or HRP-1 cells as controls. In a separate experiment on day 12, hysterectomy was performed to remove the intrinsic source of PLs. These rats received Rcho-1 cells, HRP-1 cells, or nothing. Intracerebroventricular (i.c.v.) injection of Rcho-1 into hysterectomized rats was done to examine the effect of PL replacement. Sham-hysterectomy was also performed as a control. Animals were sacrificed 2 days after each treatment at 0200 h, 1400 h, and 1800 h. Brains were used for dual immunocytochemistry of Fos/beta-endorphin. The neuronal activity of beta-endorphinergic neurons of HRP-1 i.c.v. injected animals showed a daily rhythm, with high levels at 0200 h and 1800 h, and a low level at 1400 h. These animals also exhibited two surges of PRL secretion on day 6 of pregnancy. This rhythmicity of beta-endorphinergic neurons was also observed in Rcho-1 i.c.v. injected animals, which showed very low and unchanging PRL levels. However, the magnitude of neuronal activity was reduced. On day 14 of pregnancy, all four experimental groups showed diurnal rhythms of beta-endorphinergic neurons. This rhythmicity occurred even though PRL was elevated at all three time points in the hysterectomized rats and very low in the Rcho-1 i.c.v. injected hysterectomized and sham-hysterectomized rats. Our results demonstrate that there is a diurnal rhythm of beta-endorphinergic neuronal activity in the mediobasal hypothalamus during pregnancy in the rat. PLs might reduce the neuronal activity of beta-endorphinergic neurons, but only during the first half of pregnancy, partially explaining the suppression of PRL surges.

Authors+Show Affiliations

Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160-7401, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

10433997

Citation

Lee, Y, and J L. Voogt. "Rhythmicity of Beta-endorphinergic Neuronal Activity in the Mediobasal Hypothalamus During Pregnancy in the Rat." Brain Research, vol. 837, no. 1-2, 1999, pp. 152-60.
Lee Y, Voogt JL. Rhythmicity of beta-endorphinergic neuronal activity in the mediobasal hypothalamus during pregnancy in the rat. Brain Res. 1999;837(1-2):152-60.
Lee, Y., & Voogt, J. L. (1999). Rhythmicity of beta-endorphinergic neuronal activity in the mediobasal hypothalamus during pregnancy in the rat. Brain Research, 837(1-2), 152-60.
Lee Y, Voogt JL. Rhythmicity of Beta-endorphinergic Neuronal Activity in the Mediobasal Hypothalamus During Pregnancy in the Rat. Brain Res. 1999 Aug 7;837(1-2):152-60. PubMed PMID: 10433997.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Rhythmicity of beta-endorphinergic neuronal activity in the mediobasal hypothalamus during pregnancy in the rat. AU - Lee,Y, AU - Voogt,J L, PY - 1999/8/6/pubmed PY - 1999/8/6/medline PY - 1999/8/6/entrez SP - 152 EP - 60 JF - Brain research JO - Brain Res VL - 837 IS - 1-2 N2 - During the first half of gestation in the rat, prolactin (PRL) from the anterior pituitary gland exerts its luteotropic function on the ovary to stimulate progesterone secretion. During this period, beta-endorphin stimulates PRL secretion by regulation of dopaminergic neurons in the hypothalamus. During the second half, placental lactogens (PLs) take the place of PRL in maintenance of pregnancy, and initiate a negative feedback to suppress PRL secretion. However, the effect of PLs on beta-endorphinergic neurons is not known. The aim of this study was to examine the possibility that PLs suppress PRL secretion by inhibiting beta-endorphinergic neuronal activity. To accomplish this aim, we examined the changes in the neuronal activity of beta-endorphinergic neurons in the mediobasal hypothalamus, as measured by Fos immunoreactivity, after manipulating the levels of PRL and PLs during pregnancy. On day 4 of pregnancy, animals received either Rcho-1 cells in the lateral ventricle that secrete PLs or HRP-1 cells as controls. In a separate experiment on day 12, hysterectomy was performed to remove the intrinsic source of PLs. These rats received Rcho-1 cells, HRP-1 cells, or nothing. Intracerebroventricular (i.c.v.) injection of Rcho-1 into hysterectomized rats was done to examine the effect of PL replacement. Sham-hysterectomy was also performed as a control. Animals were sacrificed 2 days after each treatment at 0200 h, 1400 h, and 1800 h. Brains were used for dual immunocytochemistry of Fos/beta-endorphin. The neuronal activity of beta-endorphinergic neurons of HRP-1 i.c.v. injected animals showed a daily rhythm, with high levels at 0200 h and 1800 h, and a low level at 1400 h. These animals also exhibited two surges of PRL secretion on day 6 of pregnancy. This rhythmicity of beta-endorphinergic neurons was also observed in Rcho-1 i.c.v. injected animals, which showed very low and unchanging PRL levels. However, the magnitude of neuronal activity was reduced. On day 14 of pregnancy, all four experimental groups showed diurnal rhythms of beta-endorphinergic neurons. This rhythmicity occurred even though PRL was elevated at all three time points in the hysterectomized rats and very low in the Rcho-1 i.c.v. injected hysterectomized and sham-hysterectomized rats. Our results demonstrate that there is a diurnal rhythm of beta-endorphinergic neuronal activity in the mediobasal hypothalamus during pregnancy in the rat. PLs might reduce the neuronal activity of beta-endorphinergic neurons, but only during the first half of pregnancy, partially explaining the suppression of PRL surges. SN - 0006-8993 UR - https://www.unboundmedicine.com/medline/citation/10433997/Rhythmicity_of_beta_endorphinergic_neuronal_activity_in_the_mediobasal_hypothalamus_during_pregnancy_in_the_rat_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0006-8993(99)01603-0 DB - PRIME DP - Unbound Medicine ER -