Altered plasma corticosterone responses during lactation in mice of two inbred strains.
Plasma corticosterone levels during lactation were examined in inbred A/J (A) and C57BL/6J (C) mice. Following shock, lactating A females showed a diminished corticosterone response relative to nonlactating controls on day 5 of lactation, but not on day 12. In contrast, plasma corticosterone levels of lactating C females 5 and 15 min following shock were lower than those of controls on day 12, but not on day 5. Consistent with these findings, lactating A females had significantly lower plasma levels of corticosterone 15 min following nonnociceptive treatments (involving distrubance, exposure to novelty, and pup manipulation) when tested on day 5 then they did when tested on day 12, whereas lactating C females had lower levels on day 12 than on day 5. Lactating females of each strain showed the same response to shock on day 12 if they reared A pups as they did if they reared C pups. This indicates that the difference found between the strains on day 12 was due to a difference in some property of A and C mothers, rather than to a difference in a characteristic, such as suckling patterns, of the pups of the two strains. It was also found that at long intervals following shock (45 and 90 min) 5-day lactating C females had higher levels of plasma corticosterone than did controls. There was no effect of lactation on resting adrenocorticoid levels in A or C females at either 5 or 12 days. The results indicate that laboratory mice show changes in hypothalamo-pituitary-adrenal activity during lactation which both vary with strain of the mother, and differ in several respects from those previously reported for rats.
D000818:Animals; D003345:Corticosterone / Q000097:blood*; D004597:Electroshock; D004971:Estrus; D005260:Female; D007774:Lactation; D008297:Male; D051379:Mice; D008805:Mice, Inbred A / Q000097:blood*; D008810:Mice, Inbred C57BL / Q000097:blood*; D011247:Pregnancy
D003345:Corticosterone