Neuroendocrine Mechanisms in Rodent Reproductive Aging

Randall, Patrick K.; Finch, Caleb E.

doi:10.1007/978-94-011-7674-3_18

Peptides, Hormones, and Behavior 1984

DOI: 10.1007/978-94-011-7674-3_18

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Neuroendocrine Mechanisms in Rodent Reproductive Aging

Patrick K. Randall¹,

Caleb E. Finch²

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1988

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Cited by 2 publications

References 92 publications

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Bone status of senescent female rats: Chemical, morphometric, and biomechanical analyses

Kiebzak

Smith

Howe

et al. 1988

Journal of Bone and Mineral Research

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The bone status of female rats, 6, 12, and 24 months of age was examined. Femur Ca, Pi, and osteocalcin contents, as well as biomechanical properties, were measured and correlated to physical indices and serum chemistry. Diaphyseal Ca, Pi, and osteocalcin did not change significantly with increasing age. Serum Ca and Pi concentrations were not altered in the aged rat. Immunoreactive parathyroid hormone (PTH) levels increased significantly with age, when analyzed by linear regression. Serum osteocalcin decreased progressively from 6 to 12 months (-21%) and from 12 to 24 months (-23%). Maximum breaking force required to fracture femurs at midshaft did not change with senescence. Hence, the strength of the femurs as an intact organ was not compromised in aging. However, ultimate stress, a parameter that normalizes for differences in bone geometry and size, decreased 14% from 12 to 24 months. Changes in other biomechanical parameters, including yield and ultimate deformation, strain, and modulus of elasticity, were relatively small, but statistically significant, or were negligible. Morphometric measurements indicated a progressive age-related increase in second moment of area and cortical area. Medullary area did not change with age. Therefore, strength of the intact femur was maintained by architectural compensations, although normalized tissue strength decreased in senescence. The bone status and Ca/Pi homeostasis of the female rat were compared to similar findings, reported previously, for the male animal. The results suggest that bone status and mineral metabolism were compromised in the aged female rat, but the magnitude of change was less than that found for the senescent male rat.

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Bone status of senescent female rats: Chemical, morphometric, and biomechanical analyses

Kiebzak

Smith

Howe

et al. 1988

Journal of Bone and Mineral Research

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Opioid Inhibition of Luteinizing Hormone Release Declines with Age and Acyclicity in Female Rats*

Field

Kuhn

1988

Endocrinology

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The current study assesses changes in opioid inhibition of LH secretion with age in female rats. We administered naloxone (NAL; 2 mg/kg, iv) to regularly cycling estrous rats of three age groups and measured serum LH in serial samples drawn from intraatrial catheters before and after treatment. The serum LH rise 10 min after NAL treatment in 4- to 6-month-old rats was significantly reduced (P less than 0.01) compared with that in 1.5- to 3-month-old animals, and no LH response was observed in 8- to 11-month-old rats. On early proestrus, LH secretion was also reduced 10 min after NAL treatment in older vs. younger rats, but all groups demonstrated belated LH rises 1 h after treatment during proestrus. Persistent estrous (PE) rats released less LH after NAL treatment than age-matched estrous rats (P less than 0.025). Higher dose NAL treatment did not increase LH release in estrous or PE rats. These results support the hypothesis that opioid inhibition of LH secretion diminishes with age in cycling rats. Furthermore, opioid tone is a function of estrous state as well as age. PE rats have lower opioid tone than cycling animals of the same age. Our findings suggest a possible role of diminished opiate tone in reproductive senescence.

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Neuroendocrine Mechanisms in Rodent Reproductive Aging

Cited by 2 publications

References 92 publications

Bone status of senescent female rats: Chemical, morphometric, and biomechanical analyses

Bone status of senescent female rats: Chemical, morphometric, and biomechanical analyses

Opioid Inhibition of Luteinizing Hormone Release Declines with Age and Acyclicity in Female Rats*

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