Catecholamine turnover rates in discrete hypothalamic areas and associated changes in median eminence luteinizing hormone-releasing hormone and serum gonadotropins on proestrus and diestrous day 1

Naomi Rance, Phyllis M Wise, Michael K. Selmanoff, Charles A. Barraclough

    Research output: Contribution to journalArticle

    Abstract

    We have correlated catecholamine [CA; i.e. norepinephrine (NE), dopamine (DA), and epinephrine (E)] turnover rates in discrete hypothalamic nuclei and in the median eminence (ME) with concentration changes in ME LHRH and serum LH, FSH, PRL, estradiol, and progesterone levels at various times during proestrus and diestrous day 1 in 4-day cyclic rats. CA concentrations were measured with a radioenzymatic assay at 0, 60, and 120 min after ip injection of 400 mg/kg α-methyl-p-tyrosine, and rate constants and turnover rates were calculated. In a;separate, assay NE, DA, and E were separated by two-dimensional thin layer chromatography, and concentrations and turnover rates of CAs were calculated. The microdissected hypothalamic nuclei examined for NE turnover rates included the medial preoptic nucleus (MPN), suprachiasmatic nucleus (SCN), arcuate nucleus (AN), and ME. DA turnover rates also were measured in the MPN, ME, and AN. ME LHRH and serum hormone concentrations were measured by RIA. Between 0900–1200 h, proestrous serum estradiol was elevated, but other serum hormones were basal, and CA turnover rates in the brain were low. However, ME LHRH concentrations increased significantly between 0900–1200 h on proestrus. Between 1200–1500 h, serum LH, FSH, PRL, and progesterone levels increased and ME LHRH levels declined significantly; during this time interval (1200–1400 h), a significant rise in ME NE and DA turnover rates occurred. Between 1500–1700 h on proestrus, while serum gonadotropins were still rising toward peak concentrations, increased ME NE turnover rates were maintained, but increased NE turnover rates also were evident in MPN, SCN, and AN. During this same time interval (1500–1700 h), a marked decline in ME and AN DA turnover rates occurred, although such rates remained unchanged within the MPN. There were no corresponding changes in MPN E turnover rates at any of the time intervals studied. The increased turnover rates of ME NE coupled with the concomitant decline in ME LHRH levels and the rise in plasma LH and FSH levels suggest that increased NE release may be important in initiating preovulatory LH and FSH surges. These changes in brain neurotransmitters and serum hormones are not the result of a diurnal rhythm, since corresponding changes in CA turnover rates or serum gonadotropins did not occur between 0900–1100 h and 1500–1700 h diestrous day 1.

    Original languageEnglish (US)
    Pages (from-to)1795-1802
    Number of pages8
    JournalEndocrinology
    Volume108
    Issue number5
    DOIs
    StatePublished - May 1981

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    Proestrus
    Median Eminence
    Gonadotropins
    Gonadotropin-Releasing Hormone
    Catecholamines
    Norepinephrine
    Serum
    Preoptic Area
    Arcuate Nucleus of Hypothalamus
    Dopamine
    Suprachiasmatic Nucleus
    Hormones
    Progesterone
    Estradiol
    Brain
    Thin Layer Chromatography
    Circadian Rhythm
    Epinephrine
    Neurotransmitter Agents
    Tyrosine

    ASJC Scopus subject areas

    • Endocrinology

    Cite this

    Catecholamine turnover rates in discrete hypothalamic areas and associated changes in median eminence luteinizing hormone-releasing hormone and serum gonadotropins on proestrus and diestrous day 1. / Rance, Naomi; Wise, Phyllis M; Selmanoff, Michael K.; Barraclough, Charles A.

    In: Endocrinology, Vol. 108, No. 5, 05.1981, p. 1795-1802.

    Research output: Contribution to journalArticle

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