Object Recognition Discrimination Research Articles

GluN1 and GluN2A NMDA Receptor Subunits Increase in the Hippocampus during Memory Consolidation in the Rat.

It is widely accepted that NMDA receptors (NMDAR) are required for learning and memory formation, and for synaptic plasticity induction. We have previously shown that hippocampal GluN1 and GluN2A NMDAR subunits significantly increased following habituation of rats to an open field (OF), while GluN2B remained unchanged. Similar results were obtained after CA1-long-term potentiation (LTP) induction in rat hippocampal slices. Other studies have also shown NMDAR up regulation at earlier and later time points after LTP induction or learning acquisition. In this work, we have studied NMDAR subunits levels in the hippocampus and prefrontal cortex (PFC) after OF habituation and after object recognition (OR), to find out whether rising of NMDAR subunits is a general and structure-specific feature during memory formation. In 1, 2 and 3 month old rats there was an increase in hippocampal GluN1 and GluN2A, but not in GluN2B levels 70 min after OF habituation. This rise overlaps with early phase of memory consolidation, suggesting a putative relationship between them. The increases fell down to control levels 90 min after training. Similar results were obtained in the hippocampus of adult rats 70 min after OR training, without changes in PFC. Following OF test or OR discrimination phase, NMDAR subunits remained unchanged. Hence, rising of hippocampal GluN1 and GluN2A appears to be a general feature after novel “spatial/discrimination” memory acquisition. To start investigating the dynamics and possible mechanisms of these changes, we have studied hippocampal neuron cultures stimulated by KCl to induce plasticity. GluN1 and GluN2A increased both in dendrites and neuronal bodies, reaching a maximum 75 min later and returning to control levels at 90 min. Translation and/or transcription and mobilization differentially contribute to this rise in subunits in bodies and dendrites. Our results showed that the NMDAR subunits increase follows a similar time course both in vitro and in vivo. These changes happen in the hippocampus where a spatial representation of the environment is being formed making possible short term and long term memories (STM and LTM); appear to be structure-specific; are preserved along life; and could be related to synaptic tagging and/or to memory consolidation of new spatial/discrimination information.

Effects of Acute Administration of Urtica dioica on the Novel Object-Recognition Task in Mice

Background: Urtica dioica (nettle) has a variety of uses in traditional medicine for the treatment of certain urogenital problems, gastrointestinal disorders, and diabetes. Objectives: Recent studies have implicated the effect of U. dioica on brain functions such as pain and memory. However, there is no direct evidence of the acute effects of this plant on cognition. The aim of the present study was to evaluate the effect of U. dioica aqueous extract on the novel object-recognition task (NOR) in mice. Materials and Methods: First, U. dioica aqueous extract was prepared, then adult male mice were randomly divided into four experimental groups. During the training session, the mice were placed in a box and given 5 minutes to explore two identical objects. The next day, they were again placed in the box and allowed to explore one familiar and one novel object. They received intraperitoneal injections of saline or U. dioica aqueous extract (100 mg/kg) before or immediately after the training session or before the test session of the NOR task. Results: The results showed that there was a preference for the novel object compared to the familiar one in each of the experimental groups. The object-recognition discrimination index in the group of mice that received U. dioica before training was significantly less than in the other experimental groups. There was no significant difference in the discrimination index between the other groups. U. dioica did not decrease the time spent exploring familiar and unfamiliar objects, or the total time spent exploring both objects. Conclusions: Acute administration of U. dioica impairs the object-recognition task if it is used only before the training session. This may be due to its modulation on the acquisition processing of object-recognition. U. dioica has no significant effects on the consolidation or retrieval processing stages of the NOR task. These results emphasize the unfavorable effect on cognitive function of pre-training with acute supplementation of U. dioica.