Hossein Masrouri - Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
Hossein Azizi - Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
Saeed Semnanian - Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

Background and Aim : Genetic and environmental factors play a significant role in drug addiction. Early maternal deprivation (MD) is one example of early-life stress and can make long-term alterations in brain circuits, particularly in brain regions that are involved in drug abuse. In MD animals, increment in susceptibility to drug dependence and abuse has been reported. In this study, the effect of MD on the basic activity and neuronal response to acute morphine exposure in lateral paragigantocellularis (LPGi) nucleus was studied.Methods : Male Wistar rats were used in this study. On postnatal day one (PND1), the litters were assigned to a MD paradigm. For this purpose, pups were separated from their dams daily for 3h during 14 days and taken care of until the experiment day (PND 70). Then, the basal firing rate and neuronal response to acute morphine administration of the LPGi nucleus were recorded by in vivo extracellular single unit recording.Results : Attenuation of morphine-induced inhibition and also enhancement of the onset latency of morphine effect on inhibitory LPGi neurons were observed in MD rats compared to control animals. MD also attenuated coefficient of variation of interspike intervals in LPGi neurons, inhibitory and excitatory response to morphine.Conclusion : We have shown that MD during infancy induces long-term alterations in neuronal properties of the LPGi nucleus, which are involved in opiate tolerance and dependence. Therefore, early maternal deprivation may change susceptibility to drug of abuse in adulthood.

Maternal deprivation, morphine, extracellular single unit recording , LPGi