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Objective: Oxidative stress plays a significant role in noise induced hearing loss (NIHL) as it largely participates in the mechanisms that underlie cell death after noise exposure and leads to sensorineural hearing loss. Many antioxidant drugs have been tested to prevent NIHL. Study design: We compared the protective effects of five molecules having antioxidant properties (vitamin E, ferulic acid, active CoQ10, its synthetic analogue – idebenone, and the soluble formulation CoQter) tested in our laboratory. This study has been conducted in a model of acoustic trauma in rats in which the molecules were given intraperitoneally 1 h before and once daily for three days after pure tone noise exposure (10 kHz for 1 h at 100dB SPL).We evaluated their hearing function via electrophysiological measurements at 2, 7 and 21 days and performed morphological studies with scanning electron microscopy and TUNEL assay as a parameter of apoptotic activation. Results: All molecules decreased threshold shift, reaching almos...

Gentamicin, acting as an iron chelator, activates membrane lipid peroxidation (MPL) and induces free radical formation, as observed in vitro and in vivo. Antioxidants, such as α-tocopherol, are able to suppress MLP, thus attenuating tissue damage. The present study was designed to investigate the possible protective effects of α-tocopherol on gentamicin ototoxicity. The study was carried out on albino guinea pigs (250–350 g). The animals were divided into four groups: group A (n = 4), injected with corn oil daily at a dose of 100 mg/kg body weight intramuscularly (IM); group B (n = 10), treated with corn oil at a dose of 100 mg/kg body weight and gentamicin base at a dose of 100 mg/kg body weight (IM); group C (n = 10), treated with gentamicin alone at a dose of 100 mg/kg body weight (IM); and group D (n 10), treated with gentamicin at the same dose plus α-tocopherol acetate at dose of 100 mg/kg body weight (IM). Electrocochleographic recordings were made from an implanted round-window electrode. All anim...

Sinusoidal vestibular stimulation in the horizontal plane induces periodic eye instability in the intact rabbit and the hypothesis of an intrinsically unstable velocity storage mechanism has been conceived. The present research examined the stability of the vestibulo-ocular reflex (VOR) in the vertical plane, considering that the time constant values of vertical and horizontal VORs differ and that separate regions of the vestibulo-cerebellum affect the horizontal and vertical slow VOR components differently.Normal pigmented rabbits were sinusoidally oscillated in the dark about their vertical and longitudinal axes to evoke horizontal and vertical eye responses.Frequency and peak-to-peak amplitude stimulation parameters ranged from 0.1 to 0.8 Hz and from 5 degrees to 20 degrees, respectively. During horizontal VOR, periodic alternating drift (PAD) was superimposed on the ocular response, and both peak velocity and period were directly correlated with stimulation amplitude. Vestibular stimulation in the vertical plane induced PAD: the period of vertical PAD was shorter and the amplitude smaller than the corresponding horizontal PAD values. A further difference in vertical PAD occurred in the lack of modulation of period and peak velocity by the stimulus amplitude.These results support the hypothesis of different instabilities of the velocity storage mechanism in the vertical and horizontal planes, possibly due to separate sensory-motor systems sub-serving the vertical and horizontal VORs.

The present research analysed on chronic animals the functional recovery of eye motility after impairment of the proprioceptive input at the level of the semilunar ganglion. The horizontal vestibulo-ocular reflex (HVOR) was recorded in normal pigmented rabbits before and after a partial electrolytic lesion of the semilunar ganglion. The recordings were repeated daily for 8-10 days to evaluate the recovery. Immediately after the lesion, as previously observed, HVOR slow phases were unaffected, while quick phases (QPs) showed a reduction in peak velocity and a deviation of trajectories from the horizontal plane. QP peak velocity was almost completely restored within 3-5 days, while trajectory deviation was not corrected during the observation period. Furthermore, in some animals, the variability of trajectories showed, starting from days 3-5, a progressive increase that led to a greater spatial disorganization. A process of lesion-induced plasticity takes place. but only the velocity of QPs can be recovered rapidly, while the QP trajectory impairment does not appear to be compensated substantially, which underlines a determinant role in the control of QP spatial orientation exerted by EOM proprioceptive signals.

In curarized guinea pigs, 68 neurons of the medical geniculate body (MGB) were tested with vestibular and acoustic stimulations. Single semicircular canals were stimulated thermally. Convergence of acoustic and vestibular afferences on the same MGB unit was observed. Following stimulation of the semicircular canals, activation and inhibition of urinary discharge were recorded, inhibition being predominant, while, when clicks were delivered, bursts of activity occurred. The implications of MGB in vestibular and acoustic integration are postulated.