Behavioural and neurochemical changes in response to repeated, early maternal and littermate separation in adult gerbils of both sexes and following chronic treatment with a substance P antagonist

These studies assessed whether early combined maternal and sibling separation (4 h daily, beginning on postnatal day 4) of neonatal Mongolian gerbils ( Meriones unguiculatus) would result in behavioural and neurochemical changes during adulthood that parallel some of the symptoms of major depression in humans. Studies also compared the effects on behaviour and neurochemistry of a substance P receptor antagonist (SPA, a putative antidepressant) to those of a known antidepressant (fluoxetine).;These studies indicate the potential to use gerbils, which have SP receptors that are homologous to those of humans, in future animal model studies of antidepressant treatments, although further refinement of these models for this species are needed.;Early separation (S) in female gerbils was associated with behavioural changes in the open field test (OFT), but not the tail suspension test (TST). S females also exhibited an increase in hippocampal synaptophysin levels in the dentate gyrus (DG) region of the hippocampus. S males showed a decrease in synaptophysin levels and a trend toward decreased levels of brain derived neurotrophic factor (BDNF) protein, markers associated with synaptic plasticity. Chronic drug treatment had few behavioural or neurochemical effects in the small number of gerbils of either sex available for drug studies, although SPA treatment in males had some anxiolytic-like activity in the OFT.