Rat brain hypothalamic and hippocampal monoamine and hippocampal beta-adrenergic receptor changes during pregnancy

The concentration of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites was measured in hypothalamic and hippocampal brain tissue obtained from non-pregnant, 15- or 20-day pregnant and 4-day postpartum rats. At 20 days of pregnancy, hypothalamic NA and DA concentrations were significantly decreased and their turnover increased relative to postpartum and estrous values, respectively. Hippocampal 3-methoxy-4-hydroxy-phenylglycol (MHPG) levels were significantly decreased at 15 days of pregnancy and 4 days postpartum compared to estrous and 20-day pregnant levels and the MHPG/NA ratio was significantly reduced at 4 days postpartum relative to the estrous value. Hippocampal 5-HT and 5-hydroxyindole-3-acetic acid (5-HIAA) levels were significantly decreased at 15 days of pregnancy while 5-HIAA levels and the 5-HIAA/5-HT ratio were significantly decreased at 20 days of pregnancy. Hippocampal beta-adrenergic receptor density was significantly lower at 4 days postpartum than at 15 days of pregnancy. A positive correlation was observed between plasma progesterone and hippocampal beta-adrenoceptor Kd values, suggesting a possible causal relationship between these two variables. The monoamine and beta-adrenoceptor changes which occur during pregnancy may be an important contributing factor in determining the mood changes which occur during pregnancy and postpartum.