Effects of opiate antagonists on serotonin turnover and on luteinizing hormone and prolactin secretion in estrogen- or morphine-treated rats

Mahlon Johnson, W. R. Crowley

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Previous findings indicate that estradiol benzoate (EB) acutely activates serotonergic projections in the medial preoptic area that are stimulatory to prolactin (PRL) secretion. Because opioid agonists also stimulate both PRL release and serotonin (5-HT) turnover, the present experiments tested whether endogenous opioid neurons may mediate estrogen feedback effects. In experiment 1, ovariectomized rats received either 50 μg EB or oil vehicle, and either saline or a long-acting opiate receptor blocker, nalmetrene (10 mg/kg), simultaneously, 3 h prior to decapitation. The pargyline method was used to determine 5-HT turnover; hence members of each treatment group received either saline or pargyline (75 mg/kg i.p.) 30 min prior to decapitation. Plasma PRL and luteineizing hormone (LH) concentrations were determined by radioimmunoassays, and 5-HT concentratins from microdissected, individual brain nuclei were measured by liquid chromatography with electrochemical detection. Nalmetrene blocked both the acute elevation of PRL and the increase in 5-HT turnover in the medial preoptic nucleus and ventromedial nucleus induced by EB. Nalmetrene alone also enhanced LH release and 5-HT turnover in the bed nucleus of the stria terminalis, and these effects were prevented by EB. A second study tested whether the opioid agonist, morphine, mimics estrogen effects on PRL and preoptic 5-HT turnover. Animals received saline, morphine (10 mg/kg i.p.) and/or naloxone (5 mg/kg i.p.) 30 min prior to decapitation. Simultaneously, half in each group received pargyline as above. Morphine stimulated both PRL release and medial preoptic 5-HT turnover, and naloxone prevented both effects. In addition, morphine enhanced 5-HT turnover in the central amygdala, and naloxone increased 5-HT turnover in the bed nucleus of the stria terminalis, and these changes appeared to be related to opioid-induced alterations in LH. These results suggest (1) that EB may acutely stimulate PRL secretion by actions on endogenous opioid peptide systems that increase activity in serotonergic projections to the medial preoptic nucleus, and (2) that opioid 5-HT interactions may also regulate LH secretion.

Original languageEnglish (US)
Pages (from-to)322-327
Number of pages6
JournalNeuroendocrinology
Volume38
Issue number4
DOIs
StatePublished - Jan 1 1984

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Opiate Alkaloids
Serotonin Antagonists
Luteinizing Hormone
Prolactin
Morphine
Serotonin
Estrogens
Opioid Analgesics
Pargyline
Decapitation
Preoptic Area
Naloxone
Hormones
Septal Nuclei
Opioid Peptides
Opioid Receptors
Liquid Chromatography

All Science Journal Classification (ASJC) codes

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience

Cite this

Effects of opiate antagonists on serotonin turnover and on luteinizing hormone and prolactin secretion in estrogen- or morphine-treated rats. / Johnson, Mahlon; Crowley, W. R.

In: Neuroendocrinology, Vol. 38, No. 4, 01.01.1984, p. 322-327.

Research output: Contribution to journalArticle

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