The Pathway of FITC-Dexran after Post-Aural Injection / 听力学及言语疾病杂志

ABSTRACT

Objective To investigate the possible pathway of FITC-dextran to the cochlea after post-aural injection.Methods The FITC-dextran(weight between 3 000~5 000) was chosen as a tracer in this study.A total of 200 suckling mice were randomly divided into four groups, with 50 in each group.Each animal was then administered with FITC-dextran or dextran via either post-auricular or intra-muscular injection, to a total dose of 20 μl (5 mg/ml).Samples were obtained at 0, 1/12, 1/4, 1/2, 1, 3, 5, 7, 12, and 24 hours after adminstmiceion, and the confocal technique was used to observe the distribution of the tracer.Taking into consideration the influence of spontaneous fluorescence, the fluorescence intensity ratio of the experimental and control groups was used as the final statistical data.Results FITC-dextran injected intramuscularly group: The fluorescence signal can be detected in the sigmoid sinus(SS) 3h after management, while in endolymphatic sac and cochlea at 12 h.FITC-dextran injected post-aurally group: After administration, an obvious fluorescence signal could be observed in the sigmoid sinus and endolymphatic sac immediately, cochlea at 30 min.The signal of the sigmoid sinus, endolymphatic sac and cochlea gradually increased successively, peaked at 5~15 min, 30 min and 60 min, and then decreased gradually.At 12 h, another small increases appeared, and the signal could not be detected at 24 h.Conclusion Compared with intramuscularly application, post-auricular injection can allow the drug to directly reach the endolymph.It is possible that the tracer first gathered in the SS via local blood circulation or infiltration, then entered the ES via micro-circulation around, and eventually arrived at the cochlea.