The Therapeutic Effect of the Chinese Herbal Medicine, Rehmanniae Radix Preparata, in Attention Deficit Hyperactivity Disorder via Reversal of Structural Abnormalities in the Cortex

Abstract

Rehmanniae radix preparata is extracted from wine-steaming the Rehmannia root, a scrophulariaceae plant. It has been used for thousands of years with effects of nourishing kidney-yin, benefiting essence and filling marrow based on traditional Chinese medicine (TCM) theory. Rehmanniae radix preparata has antioxidant, antisenescence, anti-inflammatory, and neuroprotective properties. It is the most popular Traditional Chinese medicinal compound (TCMC) used in attention deficit hyperactivity disorder (ADHD) therapy. However, few studies have been conducted exploring the effects and potential mechanisms of Rehmanniae radix preparata alone on ADHD. Recent studies have shown that Rehmanniae radix preparata inhibits spontaneous activity in mice, improves learning and memory in rats following thalamic arcuate nucleus injury, and exhibits antidepressant effects. Catalpol, an active component of Rehmanniae radix preparata, elevates brain-derived neurotrophic factor (BDNF), and attenuates neuronal apoptosis and energy metabolism failure. ADHD is characterized by hyperactivity-impulsivity and impairments in learning and memory. Its pathomechanism is closely related to structural abnormalities in the cortex that is mediated by dysfunction in neuronal development, apoptosis, and energy metabolism. We hypothesize that Rehmanniae radix preparata may be effective at treating ADHD by alleviating neurodevelopmental abnormalities, neuronal apoptosis, and energy metabolism failure.

Figure 1

Chemical structure of Catalpol.

Figure 2

Schematic representation of our hypothesis. (a) The TCM theory argues that a physiological and pathological deficiency of the kidney essence is pivotal in the pathogenic exuberance of yang and debilitation of brain marrow, which is closely related to pathogenesis of ADHD. (b) Rehmanniae radix preparata is a classical Chinese herbal medicine that benefits the kidney essence, fills brain marrow, and enriches the blood. As the most frequently prescribed herb for treating ADHD, Rehmanniae radix preparata improves learning and memory and inhibits spontaneous activity in animal models via central inhibition, antioxidation, and antiaging. (c) Catalpol, an important active ingredient of Rehmanniae radix preparata, has several pharmacological properties, such as protecting growth factors, alleviating energy metabolism failure, and reducing neuronal apoptosis in many other neuropsychiatric disorders. (d) Dysregulation of transcription factors (TFs) and regulatory proteins (RPs), energy metabolism failure, and neuronal apoptosis are linked to neuronal developmental disorders and result in structural abnormalities in the cortex, which is associated with ADHD. Therefore, we propose that Rehmanniae radix preparata and catalpol are promising natural medicines for the treatment of ADHD.