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Maternal behavior, milk ejection, and plasma hormones in Hatano high- and low-avoidance rats
Ryo Ohta1, Mariko Shirota, Atsushi Tohei
1Safety Testing Laboratory, Hatano Research Institute, Food and Drug Safety Center, 729-5 Ochiai, Hadano, Kanagawa 257-8523, Japan.
Hormones and Behavior
|October 9, 2002
Summary
Low-avoidance rats exhibit impaired maternal care, including delayed pup retrieval and reduced milk ejection, compared to high-avoidance rats. These deficits are linked to hormonal changes and impact pup growth.
Area of Science:
- Neuroscience
- Behavioral Genetics
- Animal Behavior
Background:
- Selective breeding created Hatano high-avoidance (HAA) and low-avoidance (LAA) rat strains.
- Previous studies indicated pup growth depends on the maternal strain in cross-fostering experiments.
Purpose of the Study:
- To investigate strain-specific differences in maternal care between HAA and LAA rat dams.
- To examine hormonal changes (prolactin, ACTH, corticosterone) during lactation in relation to maternal behavior.
Main Methods:
- Maternal behavior was assessed using nest building, home cage behavior, pup retrieval, and milk ejection tests.
- Plasma hormone concentrations were measured during lactation.
- Cross-fostering was used to control for maternal effects on pup growth.
Main Results:
- Both HAA and LAA dams built adequate nests and spent similar time with pups.
- LAA dams displayed longer pup retrieval latencies and left pups out of the nest.
- LAA dams showed reduced milk ejection, but oxytocin normalized this response.
- LAA dams had lower prolactin and higher ACTH levels during lactation; corticosterone levels were similar.
Conclusions:
- LAA dams exhibit deficits in maternal behavior and milk ejection compared to HAA dams.
- Maternal motivation and hormonal mechanisms regulating suckling are critical for pup growth.
- Avoidance behavior in rats is associated with distinct maternal care profiles.