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Prolactin response to morphine in intact and adrenalectomized lactating rats
D T Kiem1, M I Fekete, L Bartha
1Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest.
Brain Research
|November 1, 1991
Summary
Adrenal gland activity during lactation may reduce the prolactin (PRL) -releasing effects of morphine. Adrenalectomized rats showed increased PRL release in response to morphine, suggesting adrenal hyperfunction causes morphine insensitivity.
Area of Science:
- Endocrinology
- Neuropharmacology
- Reproductive Biology
Background:
- Lactation is associated with increased adrenocortical activity.
- The prolactin (PRL)-releasing effect of morphine is known to be blunted during lactation.
- Adrenocortical hormones may play a role in modulating morphine's effects on PRL release.
Purpose of the Study:
- To investigate whether increased adrenocortical activity during lactation causes the loss of morphine's prolactin-releasing effect.
- To determine the role of adrenal function in the regulation of prolactin secretion during lactation.
Main Methods:
- Studied the effect of morphine in adrenalectomized (ADX) and sham-operated lactating Wistar rats.
- Administered morphine or haloperidol intravenously to lactating rats.
- Measured plasma PRL levels and observed catalepsy as an indicator of morphine's central effects.
Main Results:
- Morphine failed to increase plasma PRL levels in sham-operated lactating rats.
- Morphine significantly increased plasma PRL levels in ADX lactating rats, irrespective of corticosterone replacement.
- Catalepsy induced by morphine was enhanced in ADX lactating rats.
- The PRL response to haloperidol was higher in ADX lactating rats.
Conclusions:
- Adrenal hyperfunction during lactation may lead to a loss of sensitivity to the prolactin-releasing effect of morphine.
- Adrenal hormones appear to play a crucial role in modulating the neuroendocrine responses to morphine during lactation.