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Background and Objectives: Learning is essential for understanding mental disorders, normal behavior, and forgetfulness. In this regard, the hippocampus plays an important role in the learning process. It has been reported that gamma-aminobutyric acid (GABA) receptors in the hippocampus are involved in learning and memory mechanisms and some diseases, such as epilepsy and Alzheimerchr('39')s. This study aimed to investigate the effect of coumarin on retention, tissue index, and GABA type A receptor gene expression in the hippocampus of male gonadectomy rats. Methods: The population of this study consisted of 40 Wistar rats, which were randomized into 5 groups (n=8 each). These groups included healthy without treatment, gonadectomized without treatment, gonadectomized receiving solvent or Dimethyl sulfoxide, and gonadectomized receiving coumarin at a dose of 3.5 mg/kg. The treatment was administered intraperitoneally once daily in 2 weeks. A shuttle box was used to test the memory retention of the rats. At the end of the research process, the rats were exterminated in accordance with research ethics. After removing the brains of rats, in each group, in four brains histology test was implemented with Niels staining, and in four other brains, the hippocampus was removed quickly. The hippocampi were placed inside the micro type and frozen with liquid nitrogen. Finally, a gene expression test was taken from the hippocampus using a real-time polymerase chain reaction. Results: Based on the findings, in the memory retention test of initial latency to enter the dark room (step through latency), the gonadectomy group showed a reduction, compared to the healthy group. Moreover, a significant decrease was observed in the number of healthy hippocampal pyramidal neurons; however, GABAA gene expression showed no significant difference. In the gonadectomy groups receiving treatments with different doses of coumarin, the amount of STL (Step Through Latency) and number of healthy pyramidal neurons in the memory retention test showed a significant decrease, compared to the gonadectomy group receiving solvent; nonetheless, a significant increase was revealed in the GABAA-α2 gene expression. Conclusion: It can be concluded that Gonadectomy caused memory impairment and coumarin affects memory impairment by increasing the GABAA-α2 gene expression and decreasing the number of healthy hippocampal neurons.

Background: Glucose increases memory in rats, and inhibit memory impairments produced by morphine. One mechanism by which glucose might act on memory via regulating the ATP-sensitive potassium channel. Objective: The aim of present study was to investigate the effects of glibenclamide on memory retention of passive avoidance learning in rats. Methods: This experimental study has been conducted in Qazvin University of Medical Sciences (2016). Forty male Wistar rats were divided into: Control, DMSO and glibenclamide groups (n=8). All rats were trained in a passive avoidance task (50 Hz, 1 mA, 3 s). DMSO (0.2 ml) or glibenclamide (1, 2, 5 mg/kg, i.p.) were injected for 10 days before training. Retention test was done 48 h later. Memory retention of each animal was measured as latency takes to enter the dark chamber. Findings: The time spent in the light chamber area before entering to the dark area and total time spent in the light chamber in the glibenclamide groups were less than control group. These times in the glibenclamide (5 mg/kg) group was significantly lower than control group (P

Learning new cues in all branches of biological organisms, ranging from unicellular organisms to mammals, occurs in different ways. In spite of their small size and short life span, insects have an extraordinary ability to learn, memorize and use environmental cues associated with the hosts and their food sources. Having the ability to learn and recalling the cues associated with the presence of prey / host is a key factor that increases the performance and foraging capacity of biocontrol agents including the ichneumonid parasitoid wasp Venturia canescens which is one of the most important parasitoids of the family Pyralidae in the world. In this research the learning ability of V. canescens in presence of peppermint and lemon odors was investigated by Y- Olfactometer. Results showed that the wasp had no significant preference towards peppermint or lemon, but after conditioning the female wasp, a meaningful difference was observed between her response to the conditioned odor (peppermint) and unconditioned odors (lemon). Her memory's lasting period continued for 27 hours after conditioning in the absence of the learned cues. Recognizing the learning ability and memory retention of the biocontrol agent V. canescens helps improve the efficiency of its application in biological control programs.