In vitro release of LHRH from the bovine pituitary stalk-median eminence: Alterations during the postpartum period

Allrich, R. D.; Parfet, J.R.; Marvin, Craig A.; Moss, G. E.; Malven, P.V.

doi:10.1016/0739-7240(85)90015-3

Cited by 5 publications

(2 citation statements)

References 18 publications

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“…Whisnant et al [9] found a greater dose of nal oxone was necessary to elicit an increase in serum LH concentrations at 2 weeks compared to 4 or 6 weeks post partum. The rapid change in ME LHRH content that oc curs with weaning of calves was associated with changes 442 Leshin/ Rund/ Kraeling/Crim/ Kiser Postpartum Differences in ß-END Neurons in opioid peptides in the POA and hypothalamus [26], In vitro LHRH release from ME of postpartum suckled cows was greater from tissue obtained at day 5 than at later times [43]. Finally, suckled anestrous cows had higher concentrations of opioid binding sites in tissue ho mogenates containing the preoptic-anterior hypothal amic regions than suckled cows that reinitiated estrous cycles [21 ].…”

Section: Discussionmentioning

confidence: 99%

Distribution of β-Endorphin Immunoreactivity in the Arcuate Nucleus and Median Eminence of Postpartum Anestrus and Luteal Phase Cows

La²,

Rr³

et al. 1992

Neuroendocrinology

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Deficiency in the secretion of luteinizing hormone-releasing hormone (LHRH) from the median eminence (ME) is one of the factors limiting reinitiation of estrous cycles following parturition in cows. In previous studies, administration of naloxone, an opioid receptor antagonist, to postpartum cows increased LH secretion, suggesting that endogenous opioids inhibit the secretion of LHRH. This study employs quantitative light microscopy to describe morphological changes in the distribution of immunoreactive β-endorphin (ir-β-END) neurons in the hypothalamus of anestrous early postpartum (EPP, days 10-16, n = 5), midpostpartum (MPP, days 33-43, n = 4) and multiparous cycling cows (CYC, months 12-14, n = 4). Cryostat sections (60 µm) of perfusion-fixed ventral diencephalon and forebrain were immunostained with anti-β-END serum via the biotin-avidin-peroxidase method or double stained sequentially with anti-LHRH serum, then anti-β-END serum. In all cows, β-END immunoreactive perikarya, mostly bipolar neurons, were located in the arcuate and periarcuate nucleus (ARC), with some perikarya in the ME. Within the ARC, the percentage area immunostained for ir-β-END was greater (p < 0.01) for the CYC than EPP cows, with MPP intermediate but not significantly different from the other groups. Consistent for all cows, the percentage area of ir-β-END in ventral ARC regions was greater (p < 0.05) than dorsal ARC regions. Fibers from these neurons coursed into the anterior hypothalamus, preoptic area and bed nucleus of stria terminalis. Ventrally projecting fibers entered the ME forming a densely staining band within the external layer. The percentage area stained was similar among all three postpartum groups. Few (1%) close associations between ir-β-END varicosities and LHRH perikarya and dendrites were found in the anterior hypothalamus and ventral preoptic regions. However, within the external lamina of the ME extensive intermingling of ir-β-END and LHRH varicosities were commonly observed. The reduced area of staining in the ARC of EPP cows compared to CYC cows may reflect an altered activity of β-END neurons during this period.

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Section: Discussionmentioning

confidence: 99%

Distribution of β-Endorphin Immunoreactivity in the Arcuate Nucleus and Median Eminence of Postpartum Anestrus and Luteal Phase Cows

La²,

Rr³

et al. 1992

Neuroendocrinology

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“…Importantly, onset of postpartum estrous cycles is characterized by a gradual increase in amplitude and frequency of LH pulse secretion which eventually culminates in estrus and ovulation [4,8,9], Although the LHRH content within the hypothalamus did not change with time postpartum [2,5,10], Malven [II] proposed that deficiency in secretion of endogenous LHRH from the hypothalamus delayed resumption of es trous cycles. Potassium-stimulated LHRH release in vitro during perifusions of the median eminence (ME) from suckled or early postpartum cows is reduced [12,13]. In ewes, parallel increases of LHRH and LH secretion occur with increasing time (days) from parturition [14].…”

Section: Introductionmentioning

confidence: 99%

Morphological Differences among Luteinizing Hormone Releasing Hormone Neurons from Postpartum and Estrous Cycling Cows

Leshin

Rund²,

Kraeling³

et al. 1992

Neuroendocrinology

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Deficiency in secretion of luteinizing hormone releasing hormone (LHRH) from the median eminence (ME) is one of the factors limiting reinitiation of estrous cycles following parturition in cows. This study employs quantitative light microscopy to describe morphological changes in LHRH neurons obtained from cows at three postpartum times. Tissues were obtained from anestrous early postpartum (EPP; days 10-16, n = 5), midpostpartum (MPP; days 33-43, n = 4), and multiparous cycling (CYC; months 12-14, n = 4) cows. Following perfusion fixation, cryostat sections (60 µm) of the ventral forebrain were immunostained with anti-LHRH serum via the biotin-avidin-peroxidase method. In all cows, LHRH perikarya formed a loosely arranged continuum, extending from anterior to posterior within the diagonal band of Broca, the lateral and medial preoptic areas, and the anterior hypothalamus. Width and length of perikarya were similar between postpartum groups. The number of dendrite-like processes per neuron (p < 0.01) and average or total length of process per neuron (p < 0.001) were greater in the CYC than in the EPP and MPP cows. Although all groups of cows contained a spectrum of lengths of dendrite-like processes, both EPP and MPP cows obtained a greater (p < 0.05) percentage of neurons with shorter processes and a smaller percentage of neurons with longer processes. Within the ME, the percentage area occupied by immunostained fibers was less (p < 0.05) in EPP cows than in MPP or CYC cows. For all groups, the area of LHRH immunostaining was greater (p < 0.001) in the external layer of lateral regions of the ME, but was similar in both internal and external layers of medial regions of the ME. Although additional ultrastructural studies are necessary to distinguish between de novo structural changes of neurons and the reduced filling of preexisting processes with immunoreactive LHRH, these data support the hypothesis of reduced activity of LHRH neurons during early to middle stages of the puerperium.

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Effects of progesterone and cortisol on the release of gonadotropin-releasing hormone from the perifused pituitary stalk-median eminence and on luteinizing hormone release from the pituitary of cows

Kawate

Inaba

Mori

1993

Animal Reproduction Science

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In vitro release of LHRH from the bovine pituitary stalk-median eminence: Alterations during the postpartum period

Cited by 5 publications

References 18 publications

Distribution of β-Endorphin Immunoreactivity in the Arcuate Nucleus and Median Eminence of Postpartum Anestrus and Luteal Phase Cows

Distribution of β-Endorphin Immunoreactivity in the Arcuate Nucleus and Median Eminence of Postpartum Anestrus and Luteal Phase Cows

Morphological Differences among Luteinizing Hormone Releasing Hormone Neurons from Postpartum and Estrous Cycling Cows

Effects of progesterone and cortisol on the release of gonadotropin-releasing hormone from the perifused pituitary stalk-median eminence and on luteinizing hormone release from the pituitary of cows

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