BACKGROUNDOuabain, a cardiac glycoside that specifically binds to Na/K-ATPase and inhibits its activity, was applied to gerbils to develop a method for studying auditory neuropathy.

METHODSOuabain was applied to the round window of the cochlea in each gerbil by using a piece of gelfoam with 3 microl or 24 microl (1 mmol/L) ouabain solution. The changes of the threshold of auditory brainstem response, cochlear function round window electrocochleography, as well as the morphological changes of the spiral ganglion cells of the cochlea were observed after application of ouabain for 24 hours or 96 hours.

RESULTSIn ouabain treated gerbils, auditory brainstem response and compound action potential thresholds showed either elevation or no response at all. However, the thresholds of cochlear microphonic and distortion product otoacoustic emissions were not affected. Degeneration and necrosis of some spiral ganglion cells in ears with applications of ouabain (24 hours, 3 microl, 1 mmol/L; 96 hours, 24 microl, 1 mmol/L ouabain). The number of spiral ganglion cells was decreased (24 hours, 3 microl, 1 mmol/L ouabain) or near to a total loss (96 hours, 24 microl, 1 mmol/L ouabain).

CONCLUSIONSThese results indicate a high degree of independence between the spiral ganglion cells and the outer hair cell systems in the cochlear transduction mechanism. The method used in this study would provide a valuable tool for studying auditory neuropathy.

Action Potentials ; drug effects ; Animals ; Cochlea ; drug effects ; physiology ; Evoked Potentials, Auditory, Brain Stem ; drug effects ; Gerbillinae ; Ouabain ; toxicity ; Spiral Ganglion ; drug effects

The aim of this study was to determine the effects of transplanted neural differentiated human mesenchymal stem cells (hMSCs) in a guinea pig model of auditory neuropathy. In this study, hMSCs were pretreated with a neural-induction protocol and transplanted into the scala tympani of the guinea pig cochlea 7 days after ouabain injury. A control model was made by injection of Hanks balanced salt solution alone into the scala tympani of the guinea pig cochlea 7 days after ouabain injury. We established the auditory neuropathy guinea pig model using 1 mM ouabain application to the round window niche. After application of ouabain to the round window niche, degeneration of most spiral ganglion neurons (SGNs) without the loss of hair cells within the organ of Corti and increasing the auditory brain responses (ABR) threshold were found. After transplantation of neural differentiated hMSCs, the number of SGNs was increased, and some of the SGNs expressed immunoreactivity with human nuclear antibody under confocal laser scanning microscopy. ABR results showed mild hearing recovery after transplantation. Based on an auditory neuropathy animal model, these findings suggest that it may be possible to replace degenerated SGNs by grafting stem cells into the scala tympani.
Animals ; Cardiotonic Agents/toxicity ; Cochlea/drug effects/pathology ; Disease Models, Animal ; Female ; Guinea Pigs ; Hearing Loss, Central/chemically induced/pathology/*therapy ; Humans ; *Mesenchymal Stem Cell Transplantation ; Mesenchymal Stem Cells/*cytology ; Neurogenesis ; Ouabain/toxicity ; Spiral Ganglion/pathology ; Transplantation, Heterologous

A growing number of researches have shown that ouabain can regulate mammalian sperm function and male reproduction by modulating the sperm motility, capacitation and acrosome reaction in vitro. This study further examined the relationship between ouabain and asthenozoospermia. In this study, the rat was intraperitoneally injected with ouabain at different concentrations (low-dose ouabain group: 12.5 μg/kg body weight per day, and high-dose ouabain group: 25 μg/kg body weight per day) for 30 days to establish the asthenozoospermia model. The sperms from 60 males with normal fertility were incubated with ouabain of gradient concentrations (10(-7)-10(-2) mol/L) for 4 h. The sperm motility was evaluated under a microscope. Moreover, the endogenous ouabain (EO) level was determined in seminal plasma of mild or severe asthenozoospermia patients and males with normal fertility by competitive inhibition ELISA. The results showed that the sperm motility was significantly diminished in the rats treated with different concentrations of ouabain. The number of motile sperms (grades a and b) was decreased greatly in a time- and dose-dependent manner in 10(-5)-10(-2) mol/L ouabain groups (P<0.01), while no obvious change in sperm motility was observed in 10(-7)-10(-6)mol/L groups even for 4-h incubation (P>0.05). Furthermore, the EO level was significantly increased in asthenozoospermia patients as compared with that in males with normal fertility (25.27±1.71 μg/L in mild asthenozoospermia patients, 26.52±1.82 μg/L in severe asthenozoospermia patients, 19.31±1.45 μg/L in normal fertility men) (P<0.01). In conclusion, rat asthenozoospermia was successfully established by intraperitoneal injection of ouabain, and 10(-5) mol/L ouabain was sufficient enough to inhibit sperm motility in vitro. Moreover, EO, a normal constituent of seminal plasma, was highly expressed in asthenozoospermia males as compared with normal fertility ones.
Animals ; Asthenozoospermia ; chemically induced ; metabolism ; physiopathology ; Disease Models, Animal ; Dose-Response Relationship, Drug ; Humans ; Injections, Intraperitoneal ; Male ; Ouabain ; metabolism ; pharmacology ; toxicity ; Rats ; Rats, Sprague-Dawley ; Semen ; metabolism ; Sperm Motility ; drug effects ; physiology ; Spermatozoa ; drug effects ; physiology ; Time Factors