Negative effect of bovine pineal gland extract and positive effect of supplemental lighting on lactation in mice.

The effect of bovine pineal extract and light duration on lactation in mice was examined in two experiments. In Exp. I, groups of lactating mice were injected intraperitoneally with 0, .5, 1.0, 2.0 and 4.0 mg extractable protein from a bovine pineal crude extract. The highest dose level was equal to .14 g of pineal tissue. Neither lit ter (eight pups per litter) weight gains, which were used as a measurement of milk yield, .nor dam weight gains were different (P>.10) among t reatment groups in a 14-day lactation period. In Exp. II, groups of lactating mice (14 day lactation period) on two light schedules (16 hr vs 8 hr light per day) were injected daily, intraperitoneally, with a further purified (ultragentrifugated) pineal extract at dose levels of 0, .4 and .8 mg extractable protein per injection. The highest dose level was equal to .50 g of pineal tissue. The pineal extract had a negative linear effect (P<.001) on total l i t ter (eight pups per litter) weight gain. The dam weight gain was not (P>.10) affected by injections of pineal extract. Litters from the 16-hr light group gained more weight (P<.10) than the 8-hr light group. The dam weight gain was higher (P<.01) for the 16-hr light group compared with the 8-hr light group. There was no interaction between light duration and administrat ion of pineal extract . (