Ultrastructural and pharmacological studies on the afferent synapse of lateral-line sensory cells of the African clawed toad, Xenopus laevis

1975 ◽  
Vol 163 (2) ◽  
Author(s):  
P. Monaghan
Keyword(s):  
Xenopus Laevis ◽  
Lateral Line ◽  
Sensory Cells ◽  
Pharmacological Studies ◽  
Afferent Synapse

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

scholarly journals Comparative actions of gaba and acetylcholine on the Xenopus laevis lateral line

1985 ◽  
Vol 80 (2) ◽  
pp. 313-318 ◽  
Author(s):  
R.P. Bobbin ◽  
S.C. Bledsoe ◽  
S. Winbery ◽  
G. Ceasar ◽  
G.L. Jenison
Keyword(s):  
Xenopus Laevis ◽  
Lateral Line

Extracellular Receptor Potentials from the Lateral-Line Organ of Xenopus Laevis

1980 ◽  
Vol 86 (1) ◽  
pp. 63-77
Author(s):  
ALFONS B. A. KROESE ◽  
JOHAN M. VAN DER ZALM ◽  
JOEP VAN DEN BERCKEN
Keyword(s):  
Xenopus Laevis ◽  
Lateral Line ◽  
Hair Cells ◽  
Water Displacement ◽  
Stimulus Amplitude ◽  
Nerve Fibres ◽  
Large Stimulus ◽  
Sensory Hair ◽  
Lateral Line Organ ◽  
Line Organ

1. The response of the epidermal lateral-line organ of Xenopus laevis to stimulation was studied by recording extracellular receptor potentials from the hair cells in single neuromasts in isolated preparations. One neuromast was stimulated by local, sinusoidal water movements induced by a glass sphere positioned at a short distance from the neuromast. 2. The amplitudes of the extracellular receptor potentials were proportional to the stimulus amplitude over a range of 20 dB. The phase of the extracellular receptor potentials with respect to water displacement was independent of the stimulus amplitude. 3. With large stimulus amplitude, and stimulus frequencies between 0.5 Hz and 2 Hz, the extracellular receptor potentials, and responses of single afferent nerve fibres, showed a phase lead of 1.2 π radians with respect to water displacement, i.e. they were almost in phase with water acceleration. 4. It is concluded that under conditions of stimulation with small-amplitude water movements, the hair cells respond to sensory hair displacement, whereas under conditions of stimulation with large-amplitude water movements they respond to sensory hair velocity.

The central projections of lateral line and cutaneous sensory fibres (VII and X) in Xenopus laevis

1982 ◽  
Vol 216 (1204) ◽  
pp. 279-297 ◽  
Keyword(s):  
Xenopus Laevis ◽  
Reticular Formation ◽  
Lateral Line ◽  
Functional Significance ◽  
Contralateral Side ◽  
Central Projections ◽  
Posterior Portion ◽  
Sensory Nucleus ◽  
Spinal Pathway ◽  
Central Terminal

The central terminal fields of anterior (VII) and posterior (X) lateral line nerves, as well as the somatosensory fibres of VII and X, have been studied in Xenopus laevis by CoCl 2 backfilling of appropriate nerves followed by Timms intensification of whole brains. Lateral line fibres terminate in a dorsomedial region of the medulla that extends from the auricular lobe of the cerebellum to the obex. There is great overlap in the terminal fields of lateral line fibres from nerves innervating different groups of stitches.The technique also reveals second order cells within the lateral line nucleus, just ventral and medial to the zone of fibre termination. Lateral line efferent cell bodies lie within the medullary motor areas and their ventrally descending dendrites ramify profusely within the reticular formation. Somatosensory fibres of VII and X project into a totally separate medullary-spinal pathway, the tractus descendens trigemini. Collaterals of these fibres innervate an area of neuropil considered to be the most posterior portion of the trigeminal sensory nucleus. At the region of the calamus scriptus further collaterals ramify within distinct transversely arranged plexi and may decussate to inner­vate similar plexi on the contralateral side. The functional significance of these anatomical findings is discussed.

Electroreceptors and Direction Specific Arrangement in the Lateral Line System of Salamanders?

1981 ◽  
Vol 36 (5-6) ◽  
pp. 493-496 ◽  
Author(s):  
Bernd Fritzsch
Keyword(s):  
Lateral Line ◽  
Fiber Bundles ◽  
Sensory Cells ◽  
Lateral Line System ◽  
Line System ◽  
Lateral Line Organ ◽  
Posterior Lateral Line ◽  
Afferent Fibers ◽  
Lateral Line Afferents ◽  
Line Organ

Abstract The arrangement of the lateral line afferents of salamanders as revealed by transganglionic staining with horse­ radish peroxidase is described. Each lateral line organ is supplied by two fibers only. In the medulla these two afferent fibers run in separate fiber bundles. It is suggested, that only those fibers contacting lateral line sensory cells with the same polarity form together one bundle. Bundles formed by anterior or posterior lateral line afferents are also clearly separated. Beside the lateral line organs smaller pit organs are described. These organs are supplied by one afferent only which reveals an arrangement in the medulla different from that of the lateral line afferents. Based on anatomical facts, these small pit organs are considered to be electroreceptors. Centrifugally projecting neurons, most probably efferents, are described in the medulla.

scholarly journals Selective Removal of Lateral Olivocochlear Efferents Increases Vulnerability to Acute Acoustic Injury

2007 ◽  
Vol 97 (2) ◽  
pp. 1775-1785 ◽  
Author(s):  
Keith N. Darrow ◽  
Stéphane F. Maison ◽  
M. Charles Liberman
Keyword(s):  
Brain Stem ◽  
Otoacoustic Emissions ◽  
Outer Hair Cells ◽  
Cochlear Nerve ◽  
Sensory Cells ◽  
Neural Responses ◽  
Distortion Product ◽  
Auditory Brain Stem ◽  
Pharmacological Studies

Cochlear sensory cells and neurons receive efferent feedback from the olivocochlear (OC) system. The myelinated medial component of the OC system and its effects on outer hair cells (OHCs) have been implicated in protection from acoustic injury. The unmyelinated lateral (L)OC fibers target ipsilateral cochlear nerve dendrites and pharmacological studies suggest the LOC's dopaminergic component may protect these dendrites from excitotoxic effects of acoustic overexposure. Here, we explore LOC function in vivo by selective stereotaxic destruction of LOC cell bodies in mouse. Lesion success in removing the LOC, and sparing the medial (M)OC, was assessed by histological analysis of brain stem sections and cochlear whole mounts. Auditory brain stem responses (ABRs), a neural-based metric, and distortion product otoacoustic emissions (DPOAEs), an OHC-based metric, were measured in control and surgical mice. In cases where the LOC was at least partially destroyed, there were increases in suprathreshold neural responses that were frequency- and level-independent and not attributable to OHC-based effects. These interaural response asymmetries were not found in controls or in cases where the lesion missed the LOC. In LOC-lesion cases, after exposure to a traumatic stimulus, temporary threshold shifts were greater in the ipsilateral ear, but only when measured in the neural response; OHC-based measurements were always bilaterally symmetric, suggesting OHC vulnerability was unaffected. Interaural asymmetries in threshold shift were not found in either unlesioned controls or in cases that missed the LOC. These findings suggest that the LOC modulates cochlear nerve excitability and protects the cochlea from neural damage in acute acoustic injury.

The fine structure of ampullary electric receptors in Amiurus

1964 ◽  
Vol 160 (980) ◽  
pp. 345-359 ◽  
Keyword(s):  
Fine Structure ◽  
Lateral Line ◽  
Cell Group ◽  
Sensory Cells ◽  
Receptor Cells ◽  
Pit Organ ◽  
Accessory Cells ◽  
Myelinated Nerves ◽  
Square Array ◽  
Small Nerve

The small pit-organs of Amiurus have been included in the group of ampullary lateral-line organs. On morphological and physiological grounds these ampullary organs are thought to be electric receptors and not mechano-receptors; thus they can be distinguished from all other types of acoustico-lateralis organs of vertebrates. Each small pit-organ consists of a duct leading from the surface of the skin to an ampulla, beneath which there is a group of cells lying at the base of the epidermis. There are two main types of cells in this group: the receptor and the accessory cells. The apical surfaces of the receptor cells bear microvillae but no cilia: these microvillae project into the lumen of the ampulla. Myelinated nerves supply the organs at the base ; they lose their myelin sheaths before entering the cell group where they branch and innervate the receptor cells. Small nerve terminals are closely applied to the surface of the receptor cells and in some places are thought to be in synaptic contact. Near these regions characteristic dense bodies are found in the base of the receptor cells. The bodies are surrounded by an accumulation of small vesicles of about 300 to 500 Å in diameter; they resemble structures found in corresponding situations in other types of sensory cells. Dense inclusions are found in some receptor cells: these inclusions have a highly ordered fine structure which in some sections appears as a square array of dense dots having a centre-to-centre spacing of about 75 Å. These observations are discussed in relation to the supposed activity of small pit-organs as electric receptors and to their position in the group of ampullary lateral-line organs.

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