Ear Of Rat Research Articles

Vincetoxicum arnottianum ameliorate inflammation by suppressing oxidative stress and pro-inflammatory mediators in rat

Ethnopharmacological relevanceAerial parts of Vincetoxicum arnottianum (Wight) Wight (Family Apocynaceae) are used by local communities for inflammation, healing of wound and injuries and also for urticaria. Aim of studyExtract/fractions of V. arnottianum were evaluated for potential anti-inflammatory activity in rat. MethodsMethanol extract of aerial parts of V. arnottianum (VAM) was partitioned on polarity for n-hexane (VAH), ethyl acetate (VAE), butanol (VAB) and aqueous (VAA) fractions. The extract/fractions were evaluated during in vitro assay for protection against heat induced protein denaturation and Carrageenan induced paw inflammation in rat. VAM and VAE were evaluated for anti-inflammatory potential against formalin and Freund's complete adjuvant (FCA) induced inflammation in paw of rat while croton oil induced inflammation in ear of rat, respectively. The level of inflammatory mediators; IL-17, IL-1β, IL-6, TNF-α and nitric oxide (NO) was estimated in serum of rat. ResultsAll the extract/fractions used in this study exhibited anti-inflammatory activity. However, VAE (300 mg/kg) exhibited potential anti-inflammatory activity in carrageenan (78.06 ± 4.6%), formalin (54.71 ± 0.34%) and croton oil (73.12 ± 1.9%) induced edema in rat. In FCA induced inflammation model VAM and VAE showed admiring proficiencies against alteration of body weight and organ weight indices, paw edema and histological studies. In serum increased level of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-17) and NO during adjuvant-induced inflammation were more efficiently restored with VAE treatment to rat. Presence of polyphenolics; rutin, gallic acid, caffeic acid, apigenin, myricetin and quercetin was indicated in VAE. ConclusionThe results suggest the presence of anti-inflammatory constituents in V. arnottianum.

Improved postauricular surgical approach to the round window of rats

ObjectivesResearch using rat as an in-vivo model has played an important role in otological research. The rat ear anatomy has been described; however, detailed surgical procedures to access the temporal bone are limited. The authors present a technique to approach the inner ear of rat that was standardized by cadaveric dissections and later replicated in living animals. MethodsAdult Wistar albino rats were dissected via the post-auricular approach. The emphasis was on early identification of the facial nerve that formed a reliable landmark for the tympanic bulla, which in turn houses the round window and stapedial artery. The point of identification of facial nerve was postero-inferior to the external auditory meatus. The procedure was then repeated in living animals. ResultsSeventeen cadaveric rats were dissected. Initially, the investigators attempted to identify the facial nerve at its crossing over the external auditory meatus. However, that method was found to be unsatisfactory. The facial nerve was then attempted to be identified in its course postero-inferior to the external auditory meatus. The technique improved drastically, and the facial nerve was identified promptly and reliably. The procedure was then repeated in seven living rats under general anaesthesia. The major issues encountered were bleeding from the stapedial artery, hematoma of the pinna in one rat. ConclusionThis study suggests that the post-auricular approach is a feasible and less time consuming route for round window drug delivery experiments in Wistar albino rats. Recognition of anatomical landmarks, particularly the facial nerve is the key to surgery.

Functional Morphology of the Ear of the Lesser Bamboo Rat (Cannomys badius)

Abstract. The outer, middle, and inner ears were studied in the lesser bamboo rat (Cannomys badius), a subterranean rodent in Indochina. Stereoscopic dissection and micro-computed tomography were used. The middle ear of the bamboo rat was characterized by a round eardrum without pars flaccida, “freely mobile” ossicles with a reduced transversal lamina and no orbicular apophysis, an enlarged stapedial footplate, absence of the stapedial artery, no unusual inflated bulla and retention of middle-ear muscles. The inner ear exhibited an elongated and highly coiled cochlea. Some features are associated with improved low-frequency hearing but decreased hearing sensitivity, as seen in other subterranean species. Hearing frequency limits calculated based on the middle ear dimensions were 0.5–40 kHz with best sensitivity at 6–8 kHz. It seems that the ear morphology and hearing ability of the lesser bamboo rat are typically adapted for underground habitat, even though some structures deviate from the pattern of subt...

Does the morphology of the ear of the Chinese bamboo rat (Rhizomys sinensis) show "Subterranean" characteristics?

In spite of the growing interest in rodents with subterranean activity in general and the spalacids (Spalacidae) in particular, little is known about the biology of most members of this clade, such as the Chinese bamboo rat (Rhizomys sinensis). Here, we analyzed the ear morphology of R. sinensis with respect to hearing specialization for subterranean or aboveground modes of communication. It is well-known that ecology and style of life of a particular species can be reflected in morphology of its ear, its hearing and vocalization, so we expect that such information could provide us insight into its style of life and its sensory environment. The ratio between the eardrum and stapedial footplate areas, which influences the efficiency of middle ear sound transmission, suggests low hearing sensitivity, as is typical for subterranean species. The cochlea had 3.25 coils and resembled species with good low frequency hearing typical for subterranean mammals. The length of the basilar membrane was 18.9 ± 0.8 mm and its width slowly increased towards the cochlear apex from 60 to 85 μm. The mean density of outer hair cells was 344 ± 22 and of inner hair cells 114 ± 7.3 per 1 mm length of the organ of Corti, and increased apically. These values (except for relatively low hair cell density) usually characterize ears specialized for low frequency hearing. There was no evidence for an acoustic fovea. Apart of low hair cell density which is common in aboveground animals, this species has also relatively large auricles, suggesting the importance of sound localization during surface activity. The ear of the Chinese bamboo rat thus contains features typical for both aboveground and subterranean mammals and suggests that this spalacid has fossorial habits combined with regular aboveground activity.

Micro CT visualization of silver nanoparticles in the middle and inner ear of rat and transportation pathway after transtympanic injection

BackgroundSilver nanoparticles (Ag NPs) displayed strong activities in anti-bacterial, anti-viral, and anti-fungal studies and were reportedly efficient in treating otitis media. Information on distribution of AgNPs in different compartments of the ear is lacking.ObjectiveTo detect distribution of Ag NPs in the middle and inner ear and transportation pathways after transtympanic injection.MethodsContrast effect of Ag NPs in the micro CT imaging was assessed in a phantom. AgNPs at various concentrations (1.85 mM, 37.1 mM, and 370.7 mM) were administered to rat middle ear using transtympanic injection and cadaver heads were imaged using micro CT at several time points.ResultsThe lowest concentration of Ag NPs that could be visualized using micro CT was 37.1 mM. No difference was observed between the solvents, deionized H2O and saline. Ag NPs at 37.1 mM were visible in the middle ear on 7 d post-administration. Ag NPs at 370.7 mM generated signals in the middle ear, ossicular chain, round window membrane, oval window, scala tympani, and Eustachian tube for both 4 h and 24 h time points. A gradient distribution of Ag NPs from the middle ear to the inner ear was detected. The pathways for Ag NPs to be transported from the middle ear into the inner ear are round and oval windows.ConclusionThis study provided the imaging evidence that Ag NPs are able to access the inner ear in a dose-dependent manner after intratympanic administration, which is relevant to design the delivery concentration in the future clinic application in order to avoid adverse inner ear effect.

Existence of Manserin, a Secretogranin II–Derived Neuropeptide, in the Rat Inner Ear

Manserin is a 40-amino acid neuropeptide derived from rat brain. Manserin has been shown to distribute in the neuroendocrine system, such as the pituitary and adrenal glands, but it has been little studied in other organs. In this study, the authors examined localization of manserin in the inner ear of the adult Wistar rat using immunohistochemical analyses. Manserin immunoreactivity was detected in the neuronal terminals of the organ of Corti and type II spiral ganglion cells. In addition to being identified in the auditory system, manserin was detected at the synapses of the vestibular system, such as saccule, utricle, and semicircular canal. These results suggest that inner ear manserin may be involved in the function of peripheral auditory and vestibular systems.

Aquaporins and Meniere's disease

Review of the role of aquaporins in inner ear homeostasis and potential role in the pathogenesis of Meniere's disease. Recent findings include the immunolocalization of aquaporins in the inner ear of mouse, rat, and human to cell types that are likely to undergo high ionic perturbances (e.g. potassium flux) and to putative areas of endolymph resorption or cycling. The expression of aquaporins and related proteins in the human cochlea and vestibular periphery resembles the distribution found in animal models, suggesting a critical role of aquaporins in inner ear water homeostasis and their potential role in the pathogenesis of Meniere's disease.

Vestibular and cochlear ototoxicity of topical antiseptics assessed by evoked potentials.

To evaluate and compare the effect of chlorhexidine gluconate, povidoneiodine, and alcohol-three antiseptics used before ear surgery-on the function of the vestibular and cochlear parts of the sand rat's inner ear. The assessment of damage is based on the recording of vestibular evoked potentials (VsEPs) and auditory brainstem response (ABR). Prospective controlled animal study. Fat sand rats were randomly assigned to five different groups, each receiving topical application of a different agent: saline (control), gentamicin (ototoxic control), chlorhexidine, povidone-iodine, and alcohol. Right-side total labyrinthectomy was performed, and a polyethylene tube was inserted into the left (contralateral) middle ear. After baseline recordings were taken of VsEPs and ABR, each animal received five consecutive daily applications of the specific agent into the left middle ear. Three days after the fifth application, evoked potential recordings (VsEPs and ABRs) were repeated and compared with baseline measurements. Administration of saline affected neither VsEPs nor ABR. In contrast, as expected, neither of these responses could be recorded after gentamicin application. After application of chlorhexidine all waves disappeared in all sand rats. Alcohol caused the waves to disappear in some of the animals only. Povidone-iodine did not affect VsEP recordings and had only a small effect on ABR. Chlorhexidine and alcohol had a clear toxic effect on the vestibular and cochlear function of the inner ear of the sand rat, whereas povidone-iodine did not. Thus, taking into consideration that this is an animal study, it appears that povidone-iodine might be preferable to the other agents tested in disinfecting ears with a perforated tympanic membrane.

Mapping of estrogen receptors α and β in the inner ear of mouse and rat

The sex hormone estrogen is classically known to influence growth, differentiation and function of peripheral tissues of both the female and male reproductive tract, mediated through the estrogen receptors alpha and beta. The influence of estrogens on the ear and hearing is yet not fully investigated, though some studies have suggested that estrogens may influence hearing functions. The aim of this study was to map eventual estrogen receptors in the inner ear in mouse and rat. Paraffin embedded sections of mouse and rat inner ear were immunostained with antibodies against estrogen receptors alpha and beta. Estrogen receptors alpha and beta containing cells were found in the inner ear, showing a unique distribution pattern, both in the auditory pathways and in the water/ion regulating areas. The presence of estrogen receptors indicates that estrogens may have an effect on the inner ear and hearing functions.

Topical application of clobetasol 17-propionate from various cream bases by using Wistar rat as an animal model.

The effect of clobetasol 17-propionate (CP), a potent corticosteroid, participating in various cream bases on the permeation through rat skin was tested in vitro. Three commercially available formulations and three cream bases prepared in our laboratory according to Pharmacopoeia or registered patent were evaluated in this present study. The amount of CP in the receptor phase of diffusion cell was negligible in the beginning of administration due to the process of saturation of drug in skin reservoir, then the CP molecules pass through the skin directly because of the saturation of receptors in skin reservoir followed the higher flux of CP in the later period. It was suggested that the incorporation of penetration enhancers was the possible reason mainly controlling the flux of CP creams. Nevertheless, CP residue in skin and the lag time of formulations prepared in our laboratory were not significantly higher than those of commercial ones, which indicated penetration enhancer could not dominate the local pharmacological effectiveness of CP though they played a main part on the skin penetration capacity of formulations. The antiinflammatory activity of CP was assessed in the ear of Wistar rat. According to the result of antiinflammatory activity, all formulations showed significant inhibition on oedema suggesting the role of drug itself may be more important than that of vehicle in controlling the therapy efficacy.

Interaction of methylprednisolone and transient asphyxia on the inner ear of the adrenalectomized rat

Methylprednisolone has been shown clinically to have beneficial effects on certain types of hearing loss. In the current study, compound action potential (CAP) thresholds, endocochlear potentials (EPs), and potassium concentration (C K +) values in the endolymph were determined under conditions of transient asphyxia (45 seconds) and methylprednisolone treatment (24 hours) in bilateral adrenalectomized rats. Treatment with methylprednisolone significantly reduced the effect of transient asphyxia on CAP thresholds as compared with nontreated animals. Methylprednisolone did not alter the dramatic short-term reduction in the EPs produced by anoxia. Potassium concentrations in treated adrenalectomized rats were significantly lower before transient asphyxia than in nontreated adrenalectomized rats. In the nontreated rats, transient asphyxia induced a reduction in C K + levels that was not seen in the methylprednisolone-treated animals. The data support the clinical application of methylprednisolone for certain forms of hearing loss and for potassium imbalance in the endolymph. (Otolaryngol Head Neck Surg 1998;118:338-43.)

Interaction of methylprednisolone and transient asphyxia on the inner ear of the adrenalectomized rat.

Methylprednisolone has been shown clinically to have beneficial effects on certain types of hearing loss. In the current study, compound action potential (CAP) thresholds, endocochlear potentials (EPs), and potassium concentration (CK+) values in the endolymph were determined under conditions of transient asphyxia (45 seconds) and methylprednisolone treatment (24 hours) in bilateral adrenalectomized rats. Treatment with methylprednisolone significantly reduced the effect of transient asphyxia on CAP thresholds as compared with nontreated animals. Methylprednisolone did not alter the dramatic short-term reduction in the EPs produced by anoxia. Potassium concentrations in treated adrenalectomized rats were significantly lower before transient asphyxia than in nontreated adrenalectomized rats. In the nontreated rats, transient asphyxia induced a reduction in CK+ levels that was not seen in the methylprednisolone-treated animals. The data support the clinical application of methylprednisolone for certain forms of hearing loss and for potassium imbalance in the endolymph.

高血圧ラットの内耳動脈の血管病変

高血圧ラットの内耳動脈の血管病変

Effect of the middle ear reflex on sound transmission to the inner ear of rat

The effect of the acoustic middle ear reflex (MER) was quantified using electrodes chronically implanted in the middle ears of rats. Cochlear microphonics (CM) and middle ear muscle EMG were measured under light Ketamin anesthesia after stimulation with tone pulses of 5–20 kHz ranging between 75 and 120 dB SPL. With increasing intensity, the CM measured before the onset of the MER increased to a maximum amplitude and then decreased with higher SPLs. At 10 kHz this maximum was reached at 95 dB SPL, for other stimulus frequencies at higher SPLs. After a latency of 10–20 ms, CM to 10 kHz stimuli of 80–95 dB SPL were decreased by the attenuating action of the MER. The lowest threshold of the MER was also measured at 10 kHz (77 dB SPL in the mean). To stimuli greater than 100 dB SPL after a latency of 6–10 ms, the CM amplitude was increased. That this CM increase to intense stimuli is caused by the action of the MER was confirmed by control experiments such as cutting the tendons of the middle ear muscles. The CM decrease to stimuli below 100 dB SPL, as well as the increase to very intense stimuli, can be explained by sound attenuation caused by the MER, together with the nonlinear dependence of CM amplitude on stimulus level. The observed shift of the maxima of the CM input-output function by the MER to higher stimulus levels probably indicates an increase of the dynamic range of the ear.

ラット内耳におけるＣＮＰ発現

ラット内耳におけるＣＮＰ発現

先天性血管条障害ラット（Ｗｓ／Ｗｓ）の内耳病変と聴覚

先天性血管条障害ラット（Ｗｓ／Ｗｓ）の内耳病変と聴覚

Localization of ornithine decarboxylase (ODC) in the cochlea of the immature rat

Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine synthesis, is important in cochlear development. Whereas tissue specific differences in cochlear ODC activity have been demonstrated, cellular localization of ODC protein in the inner ear of the immature rat has not. ODC was localized in inner ear structures using an ODC polyclonal antibody and the effects of cycloheximide on ODC immunoreactivity and enzymatic activity were determined. Tissues demonstrating elevated enzymatic activity contained cells with the strong immunoreactivity. ODC activity was highest in the organ of Corti and lateral wall followed by the cochlear nerve. Immunoreactivity was demonstrated throughout the cochlea with intense staining of the hair cells, pillar cells, Deiter's cells, inner sulcus cells, basilar membrane, stria vascularis, spiral ganglion cell bodies and cochlear nerve fibers. Cycloheximide rapidly diminished cochlear ODC activity and expression of ODC protein. The half-life of cochlear ODC was 30 min. Localization of cellular sites of ODC is important in understanding the role of the ODC-polyamine pathway in cochlear development and will be a valuable marker for tissue damage from ototoxic agents.

Functional development of auditory sensitivity in the fetus and neonate.

The human fetus responds to sound stimuli while still in utero. The rat and cat begin to hear only after birth. Therefore neonatal rat and cat are used as models of the development of auditory sensitivity in the human fetus. The inner ear of rat responds to stimuli delivered directly to it (bone conduction) before the middle ear can conduct sounds to the inner ear. During this period, middle ear development involves mesenchyme resorption, ossicular hardening and opening of the external canal. The latter stages of inner ear development involve increased magnitude of the endocochlear potential which augments cochlear transduction and the active cochlear amplifier. These developmental stages are probably controlled by thyroid hormone which activates several genes leading to the synthesis of proteins and enzymes required for the structural and functional maturation of the ear. This likely includes the Na+,K(+)-ATPase of the stria vascularis which generates the endocochlear potential. The magnitude of the endocochlear potential is dependent on oxygen supply so that the human fetus in utero whose blood carries less oxygen than the newborn has a hypoxia-induced sensorineural hearing loss. Upon birth and transition from placental to pulmonary oxygenation, the oxygen content of blood is increased, the magnitude of the endocochlear potential is elevated and auditory sensitivity is enhanced.

Distribution of alpha-ANP in the cochlea and the vestibular organs.

The distribution of rat alpha-atrial natriuretic polypeptide (ANP) was studied in the adult inner ear of the Sprague-Dawley rat using immunohistochemical methods. Immunostaining, in particular of the subepithelial stroma cells of the spiral ligament, the spiral prominence and below neuroepithelial areas of all five vestibular organs, was identified. We hypothesize that alpha-ANP is involved in perilymphatic dynamics rather than generating endolymph. The strong staining for alpha-ANP of outer hair cells indicates specific mechanisms for volume control as compared with inner hair cells and vestibular hair cells which all lack this immunostaining. The functional significance of the specific staining of nerve calyces in only the three cristae ampullaris but not in the two maculae remains to be clarified. The positivity of epithelial cells in the endolymphatic sac supports a previous hypothesis which looks upon this organ as a pressure regulation system in the inner ear.

Expression of nerve growth factor (NGF) receptors in the developing inner ear of chick and rat.

The expression of nerve growth factor receptors (NGFRs) was studied in the developing inner ear with in situ hybridization in chick embryos and with immunocytochemistry in rat embryos to determine sites of possible functions of NGF or NGF-like molecules in inner ear development. NGFR expression in the chick otocyst and acoustic ganglion is compared with epithelial differentiation and the onset of afferent innervation as determined with fluorescent carbocyanine tracers. In the inner ear of the chick embryo, NGFR mRNA expression shows an alternating pattern in mesenchymal and epithelial tissues. NGFR mRNA is heavily expressed in the mesenchyme surrounding the otocyst (E2-3), ceases at E3-5, and reappears in a thin layer of mesenchymal cells surrounding the membraneous epithelia (E5-13). In the otocyst epithelium, NGFR mRNA expression develops in one anterior and one posterior focus at E3-4.5. NGFR mRNA is expressed in the primordia of the ampullary cristae (E5-7) and possibly the anlage of the utricle; label transiently concentrates in the planum semilunatum of the cristae ampullares and in superior portions of the semicircular canals at E9, but is not seen in differentiating hair cells. In the acoustic ganglion, NGFR mRNA expression begins at E4; at the same time, the first peripheral acoustic nerve processes penetrate the otic epithelium (E4-4.5). The acoustic ganglia remain weakly NGFR mRNA-labeled in the posthatch animal. In the rat embryo, NGFR immunoreactivity is present in the auditory placode at E9, in the periotic mesenchyme at E9-10, and in the medial half of the otocyst at E10-11. At E12, epithelial NGFR expression becomes restricted anteriorly and posteriorly in a pattern similar to that of the chick otocyst and ceases at E13. NGFR immunoreactivity appears transiently in pillar cells of the cochlea in the third week of gestation. NGFR and NGFR mRNA is expressed after E11 in the acoustic ganglia. While NGFR transcripts are expressed in the cochlear ganglion cell bodies, NGFR protein becomes restricted to neuronal processes by the third week of gestation. The vestibular, but not the cochlear (spiral) ganglia remain NGFR-labeled in the adult rat. Onset of NGFR mRNA expression in the acoustic ganglion during the period of afferent fiber ingrowth into the otocyst epithelium is consistent with the hypothesis that NGF-like molecules may have a neurotrophic function for acoustic ganglion cells. Transient expression of NGFRs in secretory cells of the vestibular endorgan and pillar cells in the organ of Corti implicate a role for neurotrophins in the differentiation of these epithelial cell types.