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Cited by 58Neuroendocrine regulation and behaviorNeuropeptides and Animal PhysiologyStress Responses and Cortisol

Chronic intracerebroventricular morphine and lactation in rats: Dependence and tolerance in relation to oxytocin neurones

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Rayner, V C, Robinson, I C, Russell, J A·1988·The Journal of Physiology
DOI 10.1113/jphysiol.1988.sp016964PMC PMC1192047
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Abstract

1. Acutely, opioids inhibit oxytocin secretion. To study the responses of oxytocin neurones during chronic opioid exposure, forty-five lactating rats were infused continuously from a subcutaneous osmotically driven mini-pump via a lateral cerebral ventricle with morphine sulphate solution from day 2 post-partum for 5-7 days; the infusion rate was increased 2- or 2.5-fold each 40 h from 10 micrograms/h initially up to 50 micrograms/h; controls were infused with vehicle (1 microliter/h, twenty-eight rats) or were untreated (eight rats). 2. Maternal behaviour was disrupted in 27% of the morphine-treated rats; in rats that remained maternal morphine did not affect body weight or water intake but increased rectal temperature by 0.82 +/- 0.14 degrees C (mean +/- S.E.M.) across the first 4 days. 3. Weight gain of the litters of maternal morphine-treated rats was reduced by 32% during 7 days, predominantly in the first day of treatment when milk transfer was also reduced. Observation of pup behaviour during suckling showed decreased frequency of milk ejections on only the second day of morphine treatment. Plasma concentration of prolactin after 6 days was similar in maternal morphine-treated and control rats, but reduced by 90% in non-maternal morphine-treated rats, indicating normal control of prolactin secretion by suckling in morphine-treated rats. 4. Oxytocin and vasopressin contents, measured by radioimmunoassay, in the supraoptic and paraventricular nuclei and in the neurohypophysis were similar between fourteen maternal morphine-treated, twelve vehicle-treated and eight untreated lactating rats; thus exposure to morphine did not involve increased production and storage of oxytocin. 5. Distribution of [3H]morphine infused intracerebroventricularly into six virgin female rats for 6 days was measured by scintillation counting of tissue extracts. Morphine concentration in the hypothalamus and neurohypophysis was 2.7 and 12.8 micrograms/g, respectively, and in blood plasma 0.75 micrograms/g. Tolerance was not due to failure of morphine infusion. In addition, naloxone (5 mg/kg s.c.) provoked typical withdrawal reactions ('wet dog' shakes, defaecation, burrowing) in lactating rats infused with morphine for 5 days. 6. Pups were suckled onto seven maternal morphine-infused and five vehicle-infused rats anaesthetized with urethane for recording of intramammary and arterial blood pressures after treatment for 5 days. The incidence and pattern of milk ejections, and mammary gland sensitivity to oxytocin were similar in the two groups.(ABSTRACT TRUNCATED AT 400 WORDS)

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Crossref · 10.1113/jphysiol.1988.sp016964

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  • The inhibition of oxytocin secretion from neural tissues by morphine underlies the mechanism by which morphine disrupts milk ejection in lactation.

    “the inhibition of OT secretion from neural tissues by morphine underlies the mechanism by which morphine disrupts milk ejection in lactation (30, 31).”

    From Oxytocin under opioid antagonism leads to supralinear enhancement of social attention (2017) · cites this paper as [31]

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Authors
Rayner, V. C., Robinson, I. C., & Russell, J. A.
Affiliations
University of Edinburgh (GB)
ORCID
Robinson, I C
Venue
The Journal of Physiology
Publisher
Wiley
Published
1988-02
Volume
396
Issue
1
Pages
319-347
ISSN
  • 0022-3751 (ISSN-L)
  • 1469-7793
DOI
10.1113/jphysiol.1988.sp016964
PMC
PMC1192047
OpenAlex
W2004463906
Cited by
58
References
44
Citations by year
2026: 1 · 2025: 1 · 2017: 1 · 2016: 1 · 2015: 1 · 2012: 2
FWCI
7.82
Type
journal article
Language
en
Open access
Licence
onlinelibrary.wiley.com/termsAndConditions#vor (vor)
Locations
  • The Journal of Physiology (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Social Sciences › Psychology › Social Psychology › Neuroendocrine regulation and behavior
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuropeptides and Animal Physiology
  • Life Sciences › Neuroscience › Behavioral Neuroscience › Stress Responses and Cortisol
Keywords
INE, morphine, intracerebroventricular infusion, lactation, opioid use disorder, opioid tolerance, oxytocin neurons, maternal behavior, prolactin, milk ejection, milk transfer, naloxone-precipitated withdrawal, neurohypophysis, supraoptic nucleus, paraventricular nucleus, hypothalamus, rectal temperature
MeSH terms
Animals, Body Weight, Carbachol, Cerebral Ventricles, Drug Tolerance, Female, Infusions, Parenteral, Lactation, Maternal Behavior, Milk Ejection, Morphine, Morphine Dependence, Naloxone, Neurons, Oxytocin, Pregnancy, Rats

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