Offspring's own serotonin transporter genotype, independently from the maternal one, increases anxiety- and depression-like behavior and alters neuroplasticity markers in rats

INTRODUCTION

Developmental changes due to early life variations in the serotonin system affect stress-related behavior and neuroplasticity in adulthood. These outcomes can be caused both by offspring's own and maternal serotonergic genotype. We aimed to dissociate the contribution of the own genotype from the influences of mother genotype.

METHODS

Sixty-six male homozygous (5-HTT-/-) and heterozygous (5-HTT+/-) serotonin transporter knockout and wild-type rats from constant 5-HTT genotype mothers crossed with varying 5-HTT genotype fathers were subjected to tests assessing anxiety- and depression-like behaviors. Additionally, we measured plasma corticosterone levels and mRNA levels of BDNF, GABA system and HPA-axis components in the prelimbic and infralimbic cortex. Finally, we assessed the effect of paternal 5-HTT genotype on these measurements in 5-HTT+/- offspring receiving their knockout allele from their mother or father.

RESULTS

5-HTT-/- offspring exhibited increased anxiety- and depression-like behavior in the elevated plus maze and sucrose preference test. Furthermore, Bdnf isoform VI expression was reduced in the prelimbic cortex. Bdnf isoform IV and GABA related gene expression was also altered but did not survive false discovery rate (FDR) correction. Finally, 5-HTT+/- offspring from 5-HTT-/- fathers displayed higher levels of anxiety- and depression-like behavior and changes in GABA, BDNF and HPA-axis related gene expression not surviving FDR correction.

LIMITATIONS

Only male offspring was tested.

CONCLUSIONS

Offspring's own 5-HTT genotype influences stress-related behaviors and Bdnf isoform VI expression, independently of maternal 5-HTT genotype. Paternal 5-HTT genotype separately influenced these outcomes. These findings advance our understanding of the 5-HTT genotype dependent susceptibility to stress-related disorders.

The Protective and Long-Lasting Effects of Human Milk Oligosaccharides on Cognition in Mammals

Over the last few years, research indicated that Human Milk Oligosaccharides (HMOs) may serve to enhance cognition during development. HMOs hereby provide an exciting avenue in the understanding of the molecular mechanisms that contribute to cognitive development. Therefore, this review aims to summarize the reported observations regarding the effects of HMOs on memory and cognition in rats, mice and piglets. Our main findings illustrate that the administration of fucosylated (single or combined with Lacto-N-neoTetraose (LNnT) and other oligosaccharides) and sialylated HMOs results in marked improvements in spatial memory and an accelerated learning rate in operant tasks. Such beneficial effects of HMOs on cognition already become apparent during infancy, especially when the behavioural tasks are cognitively more demanding. When animals age, its effects become increasingly more apparent in simpler tasks as well. Furthermore, the combination of HMOs with other oligosaccharides yields different effects on memory performance as opposed to single HMO administration. In addition, an enhanced hippocampal long-term potentiation (LTP) response both at a young and at a mature age are reported as well. These results point towards the possibility that HMOs administered either in singular or combination forms have long-lasting, beneficial effects on memory and cognition in mammals.