g., ABC, BBC, CBA, ABB, C). An alternation was defined as successive entries into the different three arms on overlapping triplet sets (i.e., ABC, CBA) [15]. The sellckchem percentage of spontaneous alternation behavior was calculated as the ratio of actual to potential alternations as follows: Percent Alternation = {Actual Alternation (i.e., ABC, CBA: 6)/[Maximum Alternation (i.e., ABCBBCCBAABBC: 13) ? 2] �� 100 = (6/11) �� 100 = 54.54% [16].2.3.4. Fluoro-Jade b Staining Fourteen days following surgery, when the behavioral tests were conducted, rats were perfused with 4% paraformaldehyde in 0.1M phosphate buffer (pH 7.4), and then the brains were extracted and placed in the same solution. The paraffin slides were mounted on gelatin-coated slides and stained with fluoro-jade b, a fluorescent staining technique for the detection of neuronal degeneration.

The staining protocol was conducted as described by Schmued, LC (2000). Briefly, the sections of the brain were immersed in xylene and then placed in a solution containing 1% sodium hydroxide in 80% alcohol, followed by 2min in 70% alcohol and 2min in distilled water, and then the slides were transferred to a solution of 0.06% potassium permanganate for 10min. Following rinsing in distilled water, the slides were placed in the fluoro-jade b staining solution (0.0004%) for about 20min. Finally, the dry slides were cleared by immersion in xylene and mounted in water-free mounting medium, DPX, and a cover slip was placed on top. The sections were inspected with a 40x objective, using the FITC filter for the observation of neuronal degeneration [17].

Data were expressed as mean �� standard error of the mean (S.E.M.) and analyzed by the SPSS statistical software package (version 17). One-way ANOVA was used to analyze the difference between groups. Post hoc between-group comparisons were done using least square difference (LSD).3. ResultsBecause there were no significant differences in the results between control, vehicle, and sham surgery groups, the results of these three groups are pooled together and shown as control group only.3.1. Behavioral ResultsA significant decrease in the passive avoidance learning and spatial Y-maze alternation scores was observed in the A�� group, in comparison with the A�� + CA group.3.1.1. Passive Avoidance Task As shown in Figure 1, there is a significant decrease in the step-through latency in the A�� group as compared to the control and the CA group (P < 0.

01). Additionally, there is a significant increase in the step-through latency in the A�� + CA group as compared to the A�� group Batimastat (P < 0.05). The mean step-through latency for the control, CA, A��, and A�� + CA groups was 202.1 �� 48.5, 187.4 �� 44.3, 18 �� 4.9, and 184.8 �� 50.5, respectively.Figure 1Step-through latency in the experimental groups (control, CA: carnosic acid, A��: Amyloid beta, and A�� + CA: carnosic acid + A��) (mean �� SEM): **P < 0.