Effects of age on β1- and β2 assessed by quantitative autoradiography

Nancy G. Weiland, Phyllis M. Wise

Research output: Contribution to journalArticlepeer-review

Abstract

Aging female rats undergo a loss of reproductive cyclicity that has been correlated with alterations in norepinephrine neuronal activity in specific hypothalamic regions involved in the regulation of gonadotropin secretion. We explored the possibility that deteriorating reproductive function may also be due to changes in the density of receptors which bind and mediate responsiveness to norepinephrine. Existing evidence suggests that β-adrenergic receptors mediate norepinephrine's inhibitory effect on luteinizing hormone (LH). Therefore, we determined whether changes in β-adrenergic receptor densities occur in specific hypothalamic nuclei associated with reproductive function. Furthermore, we wished to determine whether age affects β1- and β2-adrenergic receptor densities differentially and whether age-related changes in receptor densities are related to hormonal status and/or vaginal smear cytology of the animals. Old constant estrous rats, old persistent diestrous rats, young cycling rats on estrus, and young cycling rats on diestrus were killed at 1000 h and brain β1- and β2-adrenergic receptor densities were measured using topical autoradiographic and computerized image analysis methods which permit a high level of neuroanatomical discrimination. We analyzed β1- and β2-adrenergic receptor densities in 7 brain areas including 4 hypothalamic regions known to be important in reproductive function. The pineal gland, the molecular layer of the cerebellum and the caudate putamen were examined because they contain high concentrations of β-adrenergic receptors which have been reported to change with age. Serum luteinizing hormone was measured in the same rats. Serum LH concentrations were the same in all rats regardless of vaginal smear cytology and age. In the medial preoptic nucleus, β1-adrenergic receptor densities were elevated in old rats. In contrast, in the suprachiasmatic nucleus β2-adrenergic receptors were lower in old rats. We observed no age-associated changes in either receptor subtype in median eminence or premammillary nucleus. Both β1- and β2-adrenergic receptor concentrations decreased in the pineal gland, while only β2-receptors declined with age in the cerebellum. No age-related differences were observed in the caudate putamen. No differences in β-adrenergic receptor densities were seen between estrus and diestrus in either young or old females in any of the areas examined. These data demonstrate that multiple and diverse alterations in β-receptor densities occur with age. They occur only in selected brain regions and are not confined to one receptor subtype. Similar age-associated changes occurred in both persistent diestrous and constant estrous old rats regardless of vaginal cytology and hormonal milieu.

Original languageEnglish (US)
Pages (from-to)305-312
Number of pages8
JournalBrain Research
Volume398
Issue number2
DOIs
StatePublished - Nov 29 1986
Externally publishedYes

Keywords

  • Aging
  • Hypothalamus
  • Pineal gland
  • Quantitative autoradiography
  • β-Adrenergic receptor

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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