The effect of pentoxifylline on cochlear blood flow

Pentoxifylline response in alloxan-induced diabetic rats

CONCLUSION

This study in rats shows that pentoxifylline may reverse detrimental effects of diabetes mellitus (DM) on the auditory system.

OBJECTIVE

To investigate whether delayed auditory brainstem responses (ABRs) induced by DM improve following pentoxifylline treatment in rats.

MATERIALS AND METHODS

Baseline ABRs were recorded in 25 ears of 13 normal-hearing rats. DM was induced by a single injection of alloxan (75 mg/kg of body weight) in all rats. Following a 1-month diabetic period, ABRs were recorded in six diabetic rats. Then, pentoxifylline treatment was administered for 6 weeks (20 mg/kg in drinking water), and final ABR testing was performed. Absolute latencies of waves I, III and V, and inter-peak latency differences (IPL) of I-V were measured in each stage of the experiment. These parameters were compared to each other in a pair-wise manner.

RESULTS

All wave latencies and IPL I-V were prolonged following induction of DM. Delay in waves III and V, and IPL I-V was significant (p<0.05). Pentoxifylline improved all of the wave latencies and IPL I-V, but significant improvement was observed in waves III and V (p<0.05). There was no significant difference between baseline measurements and measurements following pentoxifylline treatment.

Pentoxifylline maintains cochlear microcirculation and attenuates temporary threshold shifts following acoustic overstimulation

The etiology of noise-induced hearing loss is poorly understood despite years of clinical experience and experimental investigations. One potential mechanism which may contribute to noise-induced temporary threshold shifts (TTS) are vascular pathologies in the microcirculation of the cochlea. Several studies have demonstrated histologic evidence of reduced cochlear blood flow following noise exposure. Recent studies utilizing intravital microscopy (IVM) complement these histologic studies and furthermore demonstrate localized ischemia during noise exposure. The purpose of the current study was to attempt to maintain cochlear blood flow during noise exposure by treating with pentoxifylline, a xanthine derivative which promotes blood flow in capillary beds. The possibility that preserved cochlear microcirculation with pentoxifylline treatment attenuates noise-induced TTS was also examined in this study. The results show treatment with pentoxifylline maintains cochlear microcirculation as assessed by continuous red blood cell movement through capillaries. Pentoxifylline treatment did not prevent vasoconstriction or increased permeability often observed in the cochlear microvasculature during noise. Treatment with this drug reduced noise-induced TTS.