Investigating Facilitatory Effects of Lithium on Methamphetamine-induced Spatial Memory Impairments in Rat.

Introduction: It has long been known that Methamphetamine (MA), as a psychostimulant, leads to long-lasting cognitive deficits. Previous studies have shown that lithium, a mood stabilizer, could facilitate cognitive ability in most of brain diseases. In current study the effects of lithium on spatial memory, hippocampal apoptosis and brain edema in METH-exposed rats are investigated. Methods: The present study 32 Wistar rats were used to examine the effects of lithium on spatial memory by the Morris water maze, hippocampal apoptosis using the TUNEL assay, and brain edema following MA administrations. Results: The findings indicated that treatment with lithium significantly ameliorated spatial learning and memory impairment in MA-treated rats. In addition, the findings showed that treatment with lithium significantly reduced brain edema and apoptosis in the CA1 neurons in MA -exposed rats. Conclusion: The results show that treatment with lithium can partially ameliorate the MA-induced neurocognitive deficits in rats, which may be related to its protective effect in the hippocampus.

Paired-pulse Inhibition and Disinhibition of the Dentate Gyrus Following Orexin Receptors Inactivation in the Basolateral Amygdala.

Introduction: The Basolateral Amygdala (BLA) substantially affects neuronal transmission and synaptic plasticity processes through the dentate gyrus. Orexin neuropeptides play different roles in the sleep/wakefulness cycle, feeding, learning, and memory. The present study aimed to investigate the function of the orexin receptors of the BLA in the hippocampal local interneuron circuits. Methods: For this, the region's paired-pulse responses from the Dentate Gyrus (DG) were recorded. Within the procedure, SB-334867-A (12µg/0.5µL) and TCS-OX2-29 (10µg/0.5µL (orexin 1 & 2 receptors antagonists, respectively), were administered into both sides of the BLA areas of the rat brain. Dimethyl Sulfoxide (DMSO) was used as the solvent in the control animals with a volume of 0.5µL. Results: Our data indicated that the Paired-pulse (PP) responses were not affected by the inactivation of the orexin receptors of the BLA. Conclusion: Due to not observing any significant changes in the short form of synaptic plasticity, after inactivation of the orexin system of the BLA, we hypothesize that the orexinergic fibers to the basolateral part of the amygdala influence the long-term synaptic efficacy; however, the primary processing of information in short-term plasticity model is not affected by the same system. The elementary processing of the data by the amygdala might happen through the action of other neurotransmitter systems. Highlights: The neuronal transmission of DG following orexin receptors antagonism of the BLA.Paired-pulse responses were not affected by the orexin 1 receptors antagonism.Paired-pulse responses were not affected by the orexin 2 receptors antagonism. Plain Language Summary: The orexinergic system has modulatory effects by sending projection fibers to several parts of the brain, such as the hippocampus and amygdala. Orexin neuropeptides activate basolateral amygdala neural circuits during different arousal states. Although, this system plays a vital role in creating appropriate behavioral reactions, the primary processing of the information in short-term plasticity model is not affected by it.