Behavioral effects of acute stimulation of κ-opioid receptors during lactation

The behavioral effects of the κ-opioid receptor agonist U69593 were examined in lactating rats. On day 5 of lactation, animals were treated with 0.1 mg/kg of U69593 to determine whether it influences general activity and maternal latencies toward pups. Because little attention has been given to the...

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Published in:Pharmacology, biochemistry and behavior biochemistry and behavior, 2008-10, Vol.90 (4), p.534-539
Main Authors: Teodorov, Elizabeth, Tomita, Aline T., Banon, Gabriela P.R., Gil, Iara G., Bernardi, Maria M., Felício, Luciano F.
Format: Article
Language:English
Subjects:
Adaptation
Analgesics, Opioid - pharmacology
Animals
Behavior, Animal - drug effects
Benzeneacetamides - pharmacology
Blotting, Western
Female
Lactation - drug effects
Lactation - psychology
Long-term effects
Maternal behavior
Morphine - pharmacology
Motivation
Pyrrolidines - pharmacology
Rats
Rats, Wistar
Receptors, Opioid, kappa - agonists
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Summary:The behavioral effects of the κ-opioid receptor agonist U69593 were examined in lactating rats. On day 5 of lactation, animals were treated with 0.1 mg/kg of U69593 to determine whether it influences general activity and maternal latencies toward pups. Because little attention has been given to the possibility that pre-mating treatment with morphine may modulate the response to κ-opioid receptor stimulation, another group of animals was submitted to the same acute challenge after abrupt withdrawal from repeated treatment with morphine sulfate during the pre-mating period (5 mg/kg on alternate days for a total of five doses). Acute κ-opioid stimulation reduced total locomotion, rearing frequency, and time spent self-grooming and increased immobility duration. These κ agonist effects were not observed in animals pretreated with morphine. Similarly, latencies to retrieve pups were longer only in animals pretreated with saline and challenged acutely with U69593. None of these effects were observed in morphine sulfate-pretreated animals. The present results suggest that pre-mating repeated exposure to morphine produces a tolerance-like effect on behavioral responses to low-dose κ-opioid receptor stimulation in active reproductive females.
ISSN:0091-3057
1873-5177
DOI:10.1016/j.pbb.2008.04.008