Effects of long-term exercise on spatial learning, memory ability, and cortical capillaries in aged rats

Abstract

Background: This study aimed to determine the effects of long-term running exercise on spatial learning, spatial memory, and cortical capillaries in aged rats.

Material and methods: Fourteen-month-old female and male Sprague-Dawley rats were randomly divided into an exercised group (EG) and a non-exercised group (NG). The EG rats were trained on treadmill running for 4 or 14 months. The NG rats were housed under identical conditions without running. Spatial learning and memory were assessed with the Morris water maze. The cortical capillary parameters were quantitatively investigated using immunohistochemical and stereological methods.

Results: The escaped latencies of the EG were significantly different from those of the NG in 18-month-old females and 28-month-old males (p<0.05). However, 28-month-old females and 18-month-old males showed no differences in escape latency between the EG and NG (p>0.05). In 28-month-old female rats, stereological techniques showed significant differences between the EG and NG in the cortical capillary volume (median, 22.55 vs. 11.42, p<0.05) and the cortical capillary surface area (median, 7474.13 vs. 3935.90, p<0.05). In 28-month-old male rats, the EG had a significantly longer total cortical capillary length (median, 530.35 vs. 156.27, p<0.05), significantly larger cortical capillary volume (median, 16.47 vs. 3.65, p<0.01), and a significantly larger cortical capillary total surface area (median, 7885.79 vs. 1957.16, p<0.01) compared with the NG group.

Conclusions: These data demonstrate that exercise improved spatial learning, memory capacity and cortical capillaries in aged rats.

Figure 1

Sequential 1-mm cerebral slabs.

Figure 2

The slab is photographed under an anatomical microscope at a magnification of 10×. A point grid is randomly superimposed on the photographed slab, and the points that touch the cortex are counted.

Figure 3

(A) An unbiased counting frame is placed on the randomly captured image. The capillary profiles are counted if they are completely inside the counting frame or partly inside it but only touching the counting lines (dotted lines). The capillary profiles are excluded if they touch the exclusion lines (solid lines). Scale bar=10 μm. (B) The points that hit the cortex and the points hitting on that hit the capillary profiles are counted. Scale bar=10 μm. (C) The intersection points between the test lines and capillary luminal surface are counted. Scale bar=10 μm.

Figure 4

(A) Comparison of the escape latencies of female rats between the 18-month-old EG and NG. (B) Comparison of the escape latencies of male rats between the 18-month-old EG and NG. ** indicates p<0.01, * indicates p<0.05. NG: non-exercised group, EG: exercised group.

Figure 5

(A) Comparison of the escape latencies of female rats between the 28-month-old EG and NG. (B) Comparison of the escape latencies of male rats between the 28-month-old EG and NG. ** indicates p<0.01, * indicates p<0.05. NG: non-exercised group, EG: exercised group.

Figure 6

Comparisons of the cortex volumes between the 28-month-old EG and NG. NG: non-exercised group, EG: exercised group. Median: median value.

Figure 7

Representative immunohistochemical staining for the cortical capillaries between 28-month-old NG and EG. The ring structure is the cortical capillary. NG: non-exercised group, EG: exercised group. Scale bar=10 μm.

Figure 8

Comparisons of the total lengths of the cortical capillaries between the 28-month-old EG and NG. * indicates p<0.05. NG: non-exercised group, EG: exercised group. Median: median value.

Figure 9

Comparisons of the total volumes of the cortical capillaries between the 28-month-old EG and NG. ** indicates p<0.01, * indicates p<0.05. NG: non-exercised group, EG: exercised group. Median: median value.

Figure 10

Comparisons of the total surface areas of the cortical capillaries between the 28-month-old EG and NG. ** indicates p<0.01, * indicates p<0.05. NG: non-exercised group, EG: exercised group. Median: median value.