Abstract:
OBJECTIVE To investigate the effects of Rehmanniae Radix Praeparata (RRP) on hyperactivity, impulsivity, and attention deficits in spontaneously hypertensive rats (SHRs), an animal model of attention deficit hyperactivity disorder (ADHD), and to explore the potential molecular mechanisms involving fibroblast growth factor 2 (FGF2), fibroblast growth factor 21 (FGF21), fibroblast growth factor receptor 1 (FGFR1), and the cyclin-dependent kinase 5 (CDK5)/p35 complex.
METHODS Wistar–Kyoto (WKY) rats served as normal controls, while SHRs were randomly assigned to the model, methylphenidate hydrochloride (MPH), and RRP groups. The open-field, elevated plus-maze, and Y-maze tests were performed to evaluate behavioral alterations related to hyperactivity, impulsivity, and attention in SHRs. Hematoxylin and eosin staining, Nissl staining, and NeuN immunofluorescence were used to assess cerebellar structural damage and neuronal pathological alterations. Western blot was performed to determine the cerebellar protein levels of FGF2, FGF21, FGFR1, CDK5, and p35.
RESULTS Compared with the SHR model group, RRP treatment produced the following effects. Behavioral testing showed that RRP significantly reduced the total distance traveled (P<0.01), mean velocity (P<0.01), and number of center-zone entries (P<0.01) in the open-field test. It also significantly reduced the number of open-arm entries(P<0.01), percentage of time spent in the open arms(P<0.01), and number of head dips (P<0.01) in the elevated plus-maze test, while significantly increasing the spontaneous alternation rate in the Y-maze test (P<0.01). Histomorphological analyses showed that RRP significantly increased the numbers of NeuN-positive and Nissl-positive neurons in the cerebellum (P<0.01) and alleviated cerebellar histopathological damage revealed by HE staining (P<0.01). Western blot showed that RRP significantly increased the cerebellar protein levels of FGF2 (P<0.01), FGF21 (P<0.05), and FGFR1 (P<0.01), as well as those of the downstream proteins p35 (P<0.01) and CDK5 (P<0.01).
CONCLUSION RRP may promote cerebellar neuronal development and preserve structural integrity by regulating FGF2, FGF21, and FGFR1 expression and the CDK5/p35 complex, thereby alleviating behavioral abnormalities associated with hyperactivity, impulsivity, and attention deficits in SHRs.