Introduction: The hippocampal nitric oxide/cGMP signaling pathway plays a crucial role in memory processing. Phosphodiesterase interacts with this signaling pathway. There are controversial reports regarding the effect of sildenafil, a phosphodiesterase inhibitor, on learning and memory. Therefore, the effects of acute administration (intrahippocampal/ intra-dentate gyrus injection) of sildenafil on long-term potentiation (LTP) of rats were investigated. Methods: The rats were anesthetized with urethane and placed in a stereotaxic device for field potential recording. After ensuring a steady-state baseline response, a single intraperitoneal injection of saline or sildenafil (2 and10 μ g/kg) was done. The population spike amplitude, the excitatory postsynaptic potentials (EPSPs) slope and paired-pulse stimuli (as an inhibitory interneuron) were compared between groups. Results: The results showed that population spike amplitude and EPSP slope significantly increased after sildenafil administration (10μ g/kg) following titanic stimulation compared with the saline group. However, the sildenafil (2μ g/kg) and control groups showed no difference regarding population spike amplitude and EPSP slope. Sildenafil had no significant effects on recurrent inhibition. Conclusion: The obtained results indicated that acute administration of sildenafil improved LTP via direct effects on the hippocampus of intact rats. Thus, sildenafil may enhance learning and memory processing by modulating the hippocampal synapse.

Introduction: Enriched Environment (EE), a complex novel environment, has been demonstrated to improve synaptic plasticity in both injured and intact animals. The present study investigated the capacity of an early environmental intervention to normalize the impairment of passive avoidance memory and Long-Term Potentiation (LTP) induced by transient bilateral common carotid artery occlusion (2-vessel occlusion, 2VO) in rats.Methods: After weaning, young Wistar rats (22 days old) were housed in EE or Standard Environment (SE) for 40 days. Transient (30-min) incomplete forebrain ischemia was induced 4 days before the passive avoidance memory test and LTP induction.Results: The transient forebrain ischemia led to impairment of passive avoidance memory and LTP induction in the Perforant Path-Dentate Gyrus (PP-DG) synapses. Interestingly, housing and growing in EE prior to 2VO was found to significantly reverse 2VO-induced cognitive and LTP impairments.Conclusion: Our results suggest that early housing and growing in EE exhibits therapeutic potential to normalize cognitive and LTP abnormalities induced by 2VO ischemic model in rats.

Changes in land use are considered as significant factors by decision makers which can be precisely evaluated by Geographic Information System (GIS) and Remote Sensing (RS) techniques. However, land use alteration should also be evaluated for monitoring and curtailing the land degradation, especially deforestation and degradation of rangelands. The present research was then carried out in the Mahidasht Watershed, a western semi-arid region in Iran for evaluating land use change during 1955-2017, using aerial photos (1955) and Landsat satellite images (TM 1989, ETM 2002 and 2017). The main land use types of the study watershed including agriculture, forest and, rangeland and mix land use boundaries were mapped for each period (1955, 1989, 2002 and 2017). Results showed that forests and rangelands suffered from accelerated destruction during 1955– 2017 period. The reduction rate in areas of forests and rangelands were 87 and 147 ha/y. In contrast, the area of rain-fed agriculture and mixed land use (mixed of the forest-rangeland, and rangeland-rain-fed) that are more vulnerable to degradation hazard were increased by 500 ha per year. Rill and gully erosion features were obviously found in converted areas, especially in the rain-fed lands, indicating siltation and other environmental problems such as deforestation and carbon dioxide emission. In addition, irrigated lands were increased by 59. 8 ha annually due to enhancing groundwater extraction through water well drilling. Currently, excessive water extraction has resulted in a negative balance of groundwater table leading to water scarcity in this area. The mix land use were found more vulnerable to soil erosion and deforestation problems.