A possible control of food intake during pregnancy in the rat.

1. Brain hypothalamic concentrations of serotonin and norepinephrine have been implicated in the control of food intake. During pregnancy and lactation a rat dam's food consumption is increased and so a study was performed to ascertain whether this was associated with changes in the hypothalamic content of serotonin and norepinephrine. 2. In the first experiment, forty-eight Sprague Dawley rat dams were given a diet containing 250 g casein/kg adlib. After 2 weeks, eight were killed and their hypothalmic analysed for the previously-mentioned neurotransmitters. The rest were mated and continued on the diet. On each of days 7, 14 and 20 of gestation, day 14 of lactation and 2 weeks after weaning of their pups a further eight dams were killed and their hypothalami assayed as described previously. Food intake was monitored throughout the experimental period. 3. The increase food intake of the dams during gestation and lactation increased to the same extent as elevation in hypothalamic norepinephrine content and depression in serotonin content. After lactation food intake returned to pre-pregnancy levels as did the hypothalamic levels of norepinephrine and serotonin. 4. By using the same experimental design but limiting the increase in food intake in pregnancy and lactation to half the expected amount the same changes were found in hypothalamic norepinephrine and serotonin contents. 5. The possibility of hypothalamic neurotransmitter contents controlling food intake is discussed.