Supplementation of maternal diet with the essential nutrient,
choline, during the second half of pregnancy in rats causes long-lasting improvements in spatial memory in the offspring and protects them from the memory decline characteristic of old age. In contrast, prenatal
choline deficiency is associated with poor performance in certain cognitive tasks. The mechanism by which
choline influences learning and memory remains unclear; however, it may involve changes to the hippocampal
cholinergic system. Previously, we showed that the hippocampi of prenatally [embryonic days (E) 11-17]
choline-deficient animals have increased synthesis of
acetylcholine (ACh) from
choline transported by the
high-affinity choline transporter (CHT) and reduced ACh content relative to the control and to the E11-17
choline-supplemented rats. In the current study, we found that, during postnatal period [postnatal days (P) 18-480], prenatal
choline deficiency increased the expression of CHT
mRNA in the septum and CHT
mRNA and
protein levels in the hippocampus and altered the pattern of CHT immunoreactivity in the dentate gyrus. CHT immunoreactivity was more prominent in the inner molecular layer in prenatally
choline-deficient rats compared to controls and prenatally
choline-supplemented animals. In addition, in all groups, we observed a population of hilar interneurons that were CHT-immunoreactive. These neurons are the likely source of the hippocampal CHT
mRNA as their number correlated with the levels of this
mRNA. The abundance of hippocampal CHT
mRNA rose between P1 and P24 and then declined reaching 60% of the P1 value by P90. These data show that prenatal availability of
choline alters its own metabolism (i.e., CHT expression). While the upregulated CHT expression during the period of prenatal
choline deficiency may be considered as a compensatory mechanism that could enhance ACh synthesis when
choline supply is low, the persistent upregulation of CHT expression subsequent to the brief period of prenatal deprivation of
choline in utero might be beneficial during
choline deficiency in adulthood.