Biomedical subjects

F Carricondo

Publications and source records attributed to F Carricondo.

6 recordsLinked to original sources

PubMed2002

Sensitivity to glutamate neurotoxicity in different developmental periods of the rat cochlea.

Cochlear neurotoxicity induced by the intraperitoneal administration of monosodium glutamate (MSG) has been analyzed during the postnatal development of the auditory receptor of the rat. The animals were treated with MSG during two postnatal periods. The electrophysiological recordings showed that MSG treatment produced a decrease in the 8th nerve compound action potential. The effect was more marked in the animals treated between the 9th and 12th postnatal day than in the others, with a qualitative decrease in neuronal density in the spiral ganglion. These results suggest that there is a period of maximum sensitivity to the cochlear neurotoxicity induced by MSG in the postnatal development of the rat.

Action Potentials↗

PubMed2002

Abnormal cochlea linked to deafness in transgenic mice expressing human cytokeratin K8.

The cytokeratin intermediate filaments have a relevant role in the proliferation and differentiation processes of epithelial cells. To provide information about the role of K8 cytokeratin during the auditory receptor differentiation, two groups of adult mice were used: TGK8-4 transgenic and control animals. The TGK8-4 transgenic mice contained 12 kb of K8 human cytokeratin (HK8) locus (Casanova et al., 1995, 1999). The functional activity of the auditory receptor was analyzed by auditory thresholds. Morphological studies demonstrate that the auditory receptors of the TGK8-4 transgenic mice are highly immature. Immunocytochemical studies were made by using two monoclonal antibodies: CAM 5-2 (recognizing K8 human cytokeratin) and Troma-1 (recognizing both mouse and human K8 cytokeratin). These demonstrated significant differences between the auditory receptors of the transgenic mice and the control mice. These functional and morphological differences clearly suggest that K8 cytokeratin has a relevant role during the differentiation and tridimensional organization of the sensory and the supporting cells of the auditory receptor.

Animals↗

PubMed2001

Cochlear microphonic potentials: a new recording technique.

A new instrumentation and a particular method for detecting and recording cochlear microphonic potentials (CMPs) are described here. The CMPs were recorded in rats by means of pure tones (4,000, 2,000, 1,000, 500, and 250 Hz) and intraepidermic electrodes; the electrocochleography technique was avoided. An experimental design that included the use of a glutamatergic agonist (kainic acid [KA]) and an aminoglycoside antibiotic (kanamycin [KANA]) was carried out to demonstrate the origin of the recorded potential. Morphological studies showed that KA selectively eliminated the afferent type I dendrites of the spiral ganglion, while the administration of KANA resulted in the absence of outer hair cells. When CMPs were recorded after KA administration, no alterations were detected. In contrast, KANA administration resulted in the absence of any selective electrophysiological activity corresponding to CMPs. All these results were compared with the recording of the compound action potential of the eighth nerve obtained by electrocochleography. These findings and the great specificity of the reproduction of the sound stimulus confirm that the CMPs can be recorded by the new equipment.

Acoustic Stimulation↗

PubMed2000

Serotonergic innervation of the organ of Corti.

The olivocochlear efferent system of the mammalian cochlea, which is divided into two lateral and medial bundles, contains numerous neuroactive substances (acetylcholine, GABA, dopamine, enkephalins, dynorphins and CGRP). These have been located at the brainstem in neurons belonging to the lateral superior olive (lateral efferent system) or in neurons of the periolivary region around the medial superior olive and the trapezoid body (medial efferent system). All of these substances were found in well-characterized projections corresponding to lateral and medial nerve fibres and terminals which connect to the type I afferent dendrites and the outer hair cells, respectively. All could be involved in the modulation of the auditory process, as is suggested by the cochlear turnover increases observed in some of them (i.e. enkephalins or dopamine) induced by sound stimulation. Recently, the presence and distribution of serotonin-containing fibres has been included in the long list of cochlear neuroactive substances. However, its highly particular peripheral pattern of distribution together with the lack of response to sound stimulation could suggest that serotonergic fibres constitute a previously unknown cochlear innervation.

Animals↗

PubMed1999

Trimetazidine prevents cochlear lesions induced by intraperitoneal and perilymphatic administration of kainic acid.

The protective activity of trimetazidine (TMZ) against cochlear neurotoxicity induced by intraperitoneal and intracochlear administration of kainic acid (KA) has been analyzed. The amplitude of the CAP N1 wave was significantly higher in KA rats pretreated with TMZ, independently of the administration route, than in those only treated with KA. However, CAP N1 amplitude of both TMZ pretreated and non-pretreated animals was always lesser than the N1 wave amplitude observed in the control group. The CAP N1 latency did not show any significant difference between KA and TMZ+KA groups except at high intensities of 8 and 12 kHz. As a complementary control, we have demonstrated that the intraperitoneal administration of TMZ (5 mg/kg) alone did not affect either the electrophysiological activity or the morphology of the auditory nerve. Morphological results fit well with electrophysiology. Some isolated swollen afferent fibers were observed in TMZ+KA cochleae, the swollen dendrites being sparser than in the KA only treated animals. In TMZ+KA animals, the cochlear apical coils were less affected than the basal coils. Our results are in agreement with recent clinical studies and suggest that TMZ could be an active drug on cochlear impairment linked to hypoxic-ischaemic syndromes.

Animals↗

PubMed1998

HPLC detection of serotonin within the rat cochlea.

This study was performed to analyse the cochlear concentrations of serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), their sources and modifications induced by noise exposure. Superior cervical ganglionectomy did not modify these concentrations. However, removal of the blood by aortic perfusion reduced significantly (about 76%) the cochlear concentration of 5-HT without affecting the 5-HIAA concentration. These results indicate that blood constitutes an important source of 5-HT to the cochlea, opposite to the superior cervical ganglion. Exposure to noise at 90 dB SPL did not modify the total cochlear concentrations of 5-HT and 5-HIAA, or the concentrations remaining after removal of the blood, suggesting that 5-HT could have a modulatory role in the cochlea distinct from that of olivocochlear neurotransmitters.

Acoustic Stimulation↗