Plasma leptin decreases during lactation in insectivorous bats

We previously demonstrated high leptin levels during late pregnancy in litt le brown bats (Myotis lucifugus). We now extend these observations to a sec ond species, the big brown bat (Eptesicus fuscus), and also report that lep tin increases after the first trimester of pregnancy. Leptin decreased to b aseline 1 week following parturition, with a half-time decay of 2 days. Dur ing lactation, leptin was significantly correlated with body mass in E. fus cus, but not in M. lucifugus. No circadian pattern of leptin was observed i n M. lucifugus. The decrease in post-partum leptin in bats may be partly ex plained by loss of putative placental leptin. The continued decrease may re flect depletion of body fat during this energy demanding period, at least i n Eptesicus. Changes in leptin during lactation appeared to be independent of circadian effects and time of sampling. Our study provides additional ev idence that leptin increases during pregnancy and declines during lactation in a free-ranging mammal, supporting the hypothesis that leptin plays impo rtant but yet undetermined roles in reproduction.