67 April 2022, Volume 8, Issue 2, Number 29 Caspian Journal of Neurological Sciences "Caspian J Neurol Sci" Journal Homepage: http://cjns.gums.ac.ir Research Paper: Morphine Consumption During Lactation Impairs Short-Term Neuronal Plasticity in Rat Offspring CA1 Neurons Fatemeh Aghighi 1 , Mohammad Shabani 2 , Sayyed Alireza Talaei 1* 1. Physiology Research Center, Institute for Basic Sciences, Kashan University of Medical Sciences, Kashan, Iran. 2. Student Research Committee, Kashan University of Medical Sciences, Kashan, Iran. * Corresponding Author: Sayyed Alireza Talaei Address: Physiology Research Center, Institute for Basic Sciences, Kashan University of Medical Sciences, Kashan, Iran. Tel: +98 (913) 3623240, Fax: +98 (31) 55621157 E-mail: talaei@kaums.ac.ir Background: Facing environmental factors during early postnatal life, directly or indirectly via mother-infant relationships, profoundly affects the structure and function of the mammals’ Central Nervous System (CNS). Objectives: This study aimed to evaluate the effect of morphine consumption during the lactation period on short-term synaptic plasticity of the hippocampal Cornu Ammonis 1 (CA1) neurons in rat offspring. Materials & Methods: In addition to a group of control mother rats (CO), three groups subcutaneously received 5 (M5), 10 (M10), or 20 (M20) mg/kg morphine every 12 hours during the lactation period. At 45 days old, following the stimulation of the Schaffers’ collaterals, basic feld Excitatory Post-Synaptic Potentials (fEPSPs) were recorded in their offspring’s hippocampal CA1 neuronal circuits. After the construction input/output curve, paired-pulse stimulations with the inter-stimulus intervals of 20, 80, and 200 ms were applied to determine the short-term synaptic plasticity, and the paired-pulse ratio was evaluated. Results: The baseline synaptic responses of the rats CA1 neurons whose mothers received 10 and 20 mg/kg morphine twice daily during the lactation period decreased compared to the CO animals (P<0.01 & P<0.001, respectively). Furthermore, compared to the controls, the Paired-Pulse Ratio (PPR) of the CA1 neural circuits of M10 and M20 rats at 20 and 80 ms Inter-Stimulus Intervals (ISI) decreased (P<0.01). Conclusion: Morphine exposure during the lactation period has a detrimental impact on the primary synaptic activity and short-term synaptic plasticity of the hippocampal CA1 neuronal circuits of rats’ offspring. Keywords: Morphine, Lactation, Neuronal plasticity, Hippocampus, Rats A B S T R A C T Citation Aghighi F, Shabani M, Talaei SA. Morphine Consumption During Lactation Impairs Short-Term Neuronal Plasticity in Rat Offspring CA1 Neurons. Caspian J Neurol Sci. 2022; 8(2):67-75. https://doi.org/10.32598/CJNS.8.29.3 Running Title Morphine Consumption During Lactation and STP https://doi.org/10.32598/CJNS.8.29.3 Use your device to scan and read the artcle online Article info: Received: 06 Dec 2021 First Revision: 25 Dec 2021 Accepted: 12 Feb 2022 Published: 01 April 2022 2018 The Authors. This is an open access article under the CC-By-NC license.