Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.11.1.7 (peroxidase)
 65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Efferent neurones within the intraganglionic spiral bundle of the guinea pig cochlea were characterized in terms of their response properties, and their pattern of termination within the receptor organ revealed by intracellular labelling with horseradish peroxidase. All neurones subsequently identified as efferent neurones had clear features of their response properties which distinguished them from primary auditory afferents. They had long latency, low maximum discharge rate and low levels of spontaneous activity under Nembutal/Innovar anaesthesia. The pattern of discharge was extremely regular, revealed by symmetrical interspike interval histograms. 49.4% responded best to ipsilateral, 43.3% to contralateral sound and a third group of 7.3% responded equally well to either ipsilateral or contralateral sound. In cochleae in good physiological condition, these efferents were as sensitive and as sharply tuned as primary afferents with the same characteristic frequencies (CFs). All efferents fully traced in histological processing terminated on the outer hair cells. Several efferents showed extensive branching beneath the inner hair cells which might represent en passant synapses with other neuronal elements. There was clear evidence of tonotopic organization of the efferent projection. The site of termination on the outer hair cells in most instances was very close to the region of the cochlea predicted from the fibres' CF and the known place-frequency map for primary afferent neurones in the guinea pig.
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PMID:Physiological and morphological characterization of efferent neurones in the guinea pig cochlea. 241 30

Cochlear efferent and afferent units were recorded from the spiral ganglion in anesthetized guinea pigs. Efferent units were identified by their regular discharge patterns and their long response latencies to tone bursts. In some cases these physiological criteria were confirmed by anatomical tracing of single axons labeled with horseradish peroxidase. Labeled efferent axons traveled in the vestibular nerve root and the intraganglionic spiral bundle, and crossed the tunnel to innervate up to 61 outer hair cells over longitudinal distances of 0.15 to 2.1 mm. Efferent units were subdivided into classes by their excitatory responses to monaural tone bursts. Fifty-seven percent responded only to ipsilateral-ear sound, 28% only to contralateral-ear sound, and 15% to sound in either ear. Tuning curves from efferent units were generally similar in shape to afferent units, often having equally low thresholds and equally high Q10s. Efferent Q10s were somewhat lower from preparations anesthetized with a Urethane/Innovar combination than from preparations anesthetized with a Nembutal/Innovar combination. Efferent units with spontaneous activity were uncommon at the start of the recording sessions but were more frequently encountered later in the experiments. Spontaneous activity could often be suppressed by tonal stimuli, even sometimes to the non-excitatory ear of Ipsi and Contra units.
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PMID:Morphology and response properties of single olivocochlear fibers in the guinea pig. 276 87