An experimental study on the efficacy of Fucong Tablet in delaying hearing loss in aged C57BL/6J mice and its pharmacological mechanism via determining content changes of calcium-binding protein in cochlear nucleus
Objective To investigate the possible pharmacodynamic mechanism of Fucong Tablet(FCT)in delaying hearing loss in aged C57BL/6J mice by determining content changes of calcium binding protein(CBP)in cochlear nucleus(CN).Methods Following auditory brain response(ABR)detection,24 C57BL/6J mice,aged 6-month,were randomly divided into two groups,i.e.FCT treatment group(FCTTG)and elderly blank control group(EBCG).The mice in FCTTG were fed with the feed mixed with FCT,while those in EBCG fed with ordinary feed,for 6 months respectively.By the end of feeding period,another 12 C57BL/6J mice aged one-month were selected as young blank control group(YBG),and ABR audiometry was carried out to determine their hearing levels among all these animals of 3 groups,followed by samples of CN tissue collected when animals put into death,with the tissue samples treated routinely.Then,the content of Nissl body(NB)and the expressive levels of calcium binding protein(PV,CR,CB)in CN were determined among all these animals in three groups by Nissl staining and IHC respectively.Results The averaged hearing threshold of mice in YBG was significantly lower than that of EBCG determined at the 6th month and the 12th month respectively,with significantly statistical differences between them(P<0.01).Animals in EBCG and FCTTG all showed elevation in hearing threshold at various degrees,with the hearing threshold of mice in EBCG elevated much obviously and with markedly statistical significance between them(P<0.05).The contents of nissl bodies,CB and CR in CN neurons of EBCG were significantly lower than those of YBG,while the content of PV was higher in EBCG than that of YBG,with statistical significances(P<0.05).However,the content of nissl bodies,CB and CR in CN neurons of FCTTG were obviously higher than that of EBCG,while PV was lower than that of EBCG,only with significantly statistical differences in the contents of nissl bodies and CB between these two groups(P<0.05).Conclusion Cochlear nucleus neurons in aged C57BL/6J mice have developed decrease in the expressive levels of CB and CR and increase in PV content,accompanied with damage in CN neurons so as leading to hearing loss.Fucong tablets can effectively delay hearing loss among elder mice,perhaps with such a related pharmacodynamic mechanism to inhibit the loss of calcium binding protein D-28K(CB)to delay senescence of neurons in cochlear nucleus.
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