The maturation of the acetylcholine system in the dentate gyrus of gerbils (Meriones unguiculatus) is affected by epigenetic factors.

The current study investigated the influence of impoverished rearing (IR) conditions and a single early methamphetamine challenge (MA; 50 mg/kg i.p.) on day 14 on the postnatal maturation of acetylcholinesterase-positive (AChE+) fibres in the hippocampal dentate gyrus (DG) of gerbils (Meriones unguiculatus). The layer-specific densities of histochemically stained AChE+ fibres were quantified in two planes of the left and right DG in young adults (day 90). Compared to enriched reared (ER) animals, the AChE+ fibre densities turned out to be higher in both the septal and the temporal plane of both hemispheres in saline treated IR and MA treated ER gerbils. The temporal plane was slightly more affected than the septal plane. In IR animals, MA treatment selectively diminished the AChE+ fibre densities in the subgranular layer of both left and right temporal DG. In conclusion, the maturation of AChE+ fibres is vulnerable to both rearing conditions and early MA challenge. The results correlate with our previous studies on the dentate cell proliferation rates and the serotonergic innervation, two parameters which are similarly affected by the experimental design. Thus, disturbances of the ACh system may impair the hippocampal plasticity and hippocampus-related cognitive and emotional function.