Functions Of GS On TrkB MRNA/BDNF Expression In NBM And Cortex Of Aged Rats

PrefaceThe cholinergic pathway between NBM and cerebral cortex serves important functional roles in conscious awareness, attention, working memory, and a number of additional mnemonic processes. Neuronal survival is dependent on continuous trophic stimulation by neurotrophic factors. Lack of neurotrophic input has been proposed as a pathomechanism leading to morphologic and functional neu-rodegeneraion. BDNF, one of the neurotrophin family, is thought to be involved in neuronal survival, morphological and biochemical differentiation, and modulation of synaptic function in the CNS. These effects of BDNF are mediated by the tyrosine receptor kinase, trkB. Both BDNF and TrkB are widely expressed in CNS. But their age - related changes in each brain area are different. In present study, we decided to investigate the changes of BDNF and its high affili-ty receptor, trkB, in NBM and neocortex during normal aging.Ginsenosides ( GS) are the major principles of ginseng and have various pharmacological actions on the central nervous system. GS have many common functions with neurotrophins, such as neurotrophic and selective neuroprotective actions. The study that whether ginsenosides could improve CNS neuron degeneration by changing the expression of neurotrophins and their receptors are very limited. In this article, we studied the modulation of GS on neurotrophins and their receptors and discuss the mechanism of GS on aged CNS.Methods24 Wistar rats Avere randomly divided into 3 groups: young group (3-5 months) , aged groups (25 - 27 months ) and GS - treated group (25 - 27 months). GS - treated group was feed with gensinosides from 17 to 25 - 27months.In situ hybridization and imaging analysis were used to investigate the age- related changes and the GS effects on trkB mRNA expression and distributionin NBM and cerebral cortex. Immunohistochemistry and imaging analysis wereused to investigate the age - related changes and the GS effects on BDNF inNBM and cortex.Results1. In situ hibridization histochemistry1.1 The trkB mRNA expression in NBM of each group Neurons in NBM of aged group went on significant age - related degeneration. The trkB mRNA expression in aged NBM decreased 12.5% compared with young group( P <0.01). Age - related changes in neurons of GS group was less than aged group, and trkB mRNA expression increased 5.6%( P<0.01). '1.2 The trkB mRNA expression in cerebral cortex of each groupThe age - related changes in cerebral cortex was similar to NBM. TrkB mRNA expression of aged cerebral cortex decreased 15. 5% compared with young group( P <0.01). The expression in GS increased 6.1% compared with aged group(P <0.01).2. Immunohistial chemisty2.1 The BDNF level in NBM of each groupThere was a significantly difference in BDNF level between aged and young NBM. BDNF level in aged NBM decreased 12.1% ( P < 0.01). No such difference was found between aged and GS group.2. 2 The BDNF expression in cerebral cortex of each groupThe lightest positive reactivity was found in aged cerebral cortex. Positive fibers of aged cortex, especially in L I - II , became to discontinue. BDNF expression of aged cerebral cortex decreased 12.1% compared with young group(P <0. 01). The expression of cerebral cortex in GS treated rats was much higher than of aged group( 10.9% increased P <0.01).