Prenatal stress enhances vulnerability to apomorphine reward and affects 5HT-1A receptor sensitivity in adult rats.

Prenatal stress has recently become known as one of the major factors influencing neurodevelopmental changes resulting in higher susceptibility to drug abuse in adults. The current investigation is aimed at evaluation of the effect of prenatal unpredictable chronic mild stress on susceptibility to apomorphine reward and functioning of 5HT-1A receptors in adulthood in male rats. The female rats were subjected to chronic mild stress from gestational day 6 until parturition. In adult animals, the place preference (CPP), as well as behavioral sensitization to repeated apomorphine (1.0 mg/kg) administration was measured, and the animals underwent behavioral testing and measurement of 5-HT syndrome, followed by analysis of 5HT and 5HIAA content in the hippocampus, hypothalamus, midbrain, and caudate nucleus after injection of 5HT-1A receptor agonist 8-OH-DPAT (1.0 mg/kg). The prenatally stressed animals demonstrated increased preference for the compartment paired with apomorphine and increased behavioral sensitization as compared to control rats, which indicates increased reward susceptibility. Furthermore, prenatally stressed animals displayed increased 5-HT syndrome behavior and lower content of 5HT and 5HIAA in some regions following 8-OH-DPAT challenge. Thus, the prenatal stress increases susceptibility to apomorphine reward through 5HT-1A receptors.