Fig 1: (A) Representative Western blot images for BDNF and NGF proteins as a function of exercise condition (VEx = Exercise; Stat = Stationary control wheels), substance coating the microbeads (PBS, TrkB-IgG; TrkA-IgG), and whether the beads were implanted on both sides of the dorsal hippocampus (bilateral) or only on one side (unilateral) in control rats. Hypoxanthine phosphoribosyltransferase 1 (HPRT1) was used as a housekeeper. (B) The mean ± SEM of percent control of BDNF with values normalized to HPRT1 levels. Relative to the stationary wheel condition (Stat), control rats that voluntarily exercised had persistent increased BDNF levels. However, both bilateral and unilateral hippocampal infusion of TrkB-IgG coated microspheres completely suppressed the exercise-induced increase in BDNF such that they were comparable to the BDNF level in sedentary rats. (C) The mean ± SEM of percent control of NGF with values normalized to HPRT1 levels. Relative to the stationary wheel condition (Stat), rats that voluntarily exercised had persistent increased NGF levels. However, unlike TrkB IgG, the infusion of TrkA IgG coated microspheres differentially suppressed exercise-induced increases in NGF as a function of whether the infusion was bilateral or unilateral within the hippocampus. Specifically, in rats that exercised, only bilateral infusion of TrkA-IgG coated microspheres led to a significant suppression of NGF, while the unilateral infusion of TrkA-IgG coated microspheres did not significantly decrease NGF levels in the hippocampus in the contralateral hemisphere.
Fig 2: Spontaneous alternation is displayed with the sequestering of NGF [(A) (TrkA-IgG) and BDNF (B) (TrkB-IgG)], and is expressed as mean percent alternation ± SEM. Exercise (green bars) completely ameliorated the spontaneous alternation impairment in PTD-treated rats; conversely, blocking NGF (light green bars) completely abolished the exercise related recovery in PTD rats, and diminished performance in PF rats. Blocking BDNF impaired performance in PF control rats, regardless of exercise status. In contrast, inhibiting the actions of BDNF had no effect on the behavior of PTD-treated rats. Microbead placement is observed from a green fluorescent image taken of the dorsal hippocampus with 5× objective lens (C).
Fig 3: Hippocampal acetylcholine (ACh) efflux measured throughout baseline (B1–B3), spontaneous alternation (M1–M3) and post-baseline (A1–A3) phases. Inset graphs represent basal ACh levels in femtomoles. PTD-treatment reduced ACh efflux during maze testing (A) vs. (B). In the no exercise condition (Stat), sequestering NGF with TrkA IgG reduced ACh efflux during maze testing in PTD rats (B). Exercise increased ACh efflux in both PF control and PTD-rats (C,D). In PTD VEx rats (D), exercise rescued the impaired ACh levels to the level of control rats. However, sequestering NGF suppressed behaviorally activated ACh efflux from exercise in both PF and PTD rats (C,D). E indicates a significant effect of exercise; T indicates a significant effect of treatment, ∗ indicates a significant effect of TrkA-IgG microbeads on basal ACh and α indicates a significant effect of blocking NGF. Within (B) is an illustrative example hippocampal placement of the microdialysis cannula. The red region represents the probe membrane.
Fig 4: Experimental timeline indicating that the subjects were randomly split between PTD and PF treatment. After treatment recovery, rats received a dorsal hippocampal infusion of either TrkB-IgG-, TrkA-IgG- or saline-coated microbeads, in addition to a cannulation to measure ACh efflux. Immediately following surgery rats were split into two groups, either a VEx (voluntary exercise) group where rats received running wheels attached to a home-cage for 2-weeks, or a Stat group (stationary) that had exposure to immobile wheels for this 2-week duration. Following the exercise exposure, rats were placed back into normal homecages and were tested 2-weeks later on a spontaneous alternation task with microdialysis to collect hippocampal ACh dialysate samples, followed by perfusion and assessment of ChAT and nestin cellular morphology in the MS/dB. The images indicating microbead delivery and hippocampal cannulations were adapted from Paxinos and Watson (Paxinos and Watson, 2014).
Fig 5: Cumulative distance ran throughout the 2-weeks of wheel running for PF rats (A) and PTD rats (B). Distance traveled is expressed as meters per day ± SEM. PTD rats ran less than control PF rats from days 3 to 14. There were no differences observed in running as a function of blocking BDNF (TrkB-IgG) or NGF (TrkA-IgG). T∗ indicates a significant effect of Treatment.
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