Complex Biphasic Changes of Neuropeptide Concentrations in the Rat Limbic System During Pregnancy and Parturition

Sex hormones including estrogens affect brain areas involved in mood and cognition in addition to directly controlling reproduction and reproductive behavior. We studied the effect of pregnancy and puerperium on the concentrations of cholecystokinin (CCK), neuropeptide Y (NPY), substance P (SP) and galanin in tissue extracts from the rat striatum, frontal cortex and the hippocampal formation by means of radioimmunoassay. The most profound effects were found in the frontal cortex. Thus, cholecystokinin-like immunoreactivity (CCK-LI) was increased by 40 % during late pregnancy (p<0.01) compared to estrous whereas SP-LI and galanin-LI decreased 25 % and 10 %, respectively. Postpartum, CCKLI decreased by 26% compared to pregnancy (p<0.05) whereas SP-LI and galanin-LI were increased to a level above estrous (SP, P<0.01; galanin, P<0.05). No significant effect was observed in NPY-LI in this area. In the striatum during late pregnancy the concentrations of cholecystokinin-LI increased by 29 % (p<0.05), NPY-LI by 22% (p<0.05) whereas SP-LI slightly increased (not significant). Postpartum, cholecystokinin-LI decreased by 25 % (p<0.01) compared to pregnancy and NPY by 16 % (p<0.01). SP continued to increase postpartum by 33 % (p<0.05) whereas no effect was observed on galanin-LI concentration. Surprisingly, we did not observe any changes in any peptide or groups measured in the hippocampal formation. The complex hormonal adjustments occurring during pregnancy and in the puerperium induce profound changes in the concentrations of several neuropeptides in regions of the rat brain involved in the control of mood