Positive modulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors differentially alters spatial learning and memory in juvenile rats younger and older than three weeks.

Remarkable performance improvements occur at the end of the third postnatal week in rodents tested in various tasks that require navigation according to spatial context. While alterations in hippocampal function at least partially subserve this cognitive advancement, physiological explanations remain incomplete. Previously, we discovered that developmental modifications to hippocampal glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in juvenile rats was related to more mature spontaneous alternation behavior in a symmetrical Y-maze. Moreover, a positive allosteric modulator of AMPA receptors enabled immature rats to alternate at rates seen in older animals, suggesting an excitatory synaptic limitation to hippocampal maturation. We then validated the Barnes maze for juvenile rats in order to test the effects of positive AMPA receptor modulation on a goal-directed spatial memory task. Here we report the effects of the AMPA receptor modulator, CX614, on spatial learning and memory in the Barnes maze. Similar to our prior report, animals just over 3 weeks of age display substantial improvements in learning and memory performance parameters compared to animals just under 3 weeks of age. A moderate dose of CX614 enabled immature animals to move more directly to the goal location, but only after 1 day of training. This performance improvement was observed on the second day of training with drug delivery or during a memory probe trial performed without drug delivery after the second day of training. Higher doses created more search errors, especially in more mature animals. Overall, CX614 provided modest performance benefits for immature rats in a goal-directed spatial memory task.

Comparative evaluation of microleakage and hardness of newer posterior restorative materials.

Background: The physical properties of restorative materials are critical when restoring posterior teeth. Restorative materials are continuously evolving in the quest for creating long lasting restorations. Aim and objective: To compare and evaluate microleakage and hardness of three different posterior restorative materials: Cention N, Zirconomer Improved and Solare Sculpt. Materials and methods: For micro leakage evaluation, 40 extracted human third molars were randomly divided into three experimental groups of 10 teeth each and two control group of 5 teeth each. Standardized box shaped class II cavity preparation was done in Group I, II, III and V. In Group V, cavity was prepared but left unrestored. No cavities were prepared in Group IV. Cavities in Group I, II, and III were restored with Cention N, Zirconomer Improved, Solare Sculpt respectively. Teeth were thermocycled together for 500 cycles. All the samples were placed in 2% methylene blue for 24 h. Microleakage evaluation was done using stereomicroscope. For hardness evaluation ten standardized discs of each material were prepared and evaluated using vicker's hardness test. Results: All the groups showed some amount of microleakage. The mean micro-leakage score was significantly more among Group II compared to Group I. There was no significant difference in mean micro-leakage score between Groups I and III. The mean hardness value was significantly more among Groups I and II compared to Group III. Conclusion: No material was able to completely eliminate microleakage. Cention N showed high hardness among the materials tested.