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Biomedical subjects

J Caston

Publications and source records attributed to J Caston.

At least 73 records · Page 4Linked to original sources
PubMed1984

Responses to somatosensory input by afferent and efferent neurons in the vestibular nerve of the frog.

In the frog, we have recorded the activity of efferent and afferent fibers in the nerve of the horizontal semicircular canal in response to somatosensory stimulation. Recordings were made extracellularly by means of glass micropipettes filled with 2 M NaCl, and somatosensory stimulation was produced either by electrical stimulation of the sciatic nerve (ipsi- or contralateral to the recording side) or by vibratory stimulation of the gastrocnemius. The discharge frequency of 43% of the efferent fibers recorded was significantly increased by such stimulation, while the activity of the others was unaffected. The discharge rate of the afferent fibers was either significantly increased (in about 11% of the cases when the results were pooled together) or significantly decreased (in about 22% of the cases) by stimulation of the somatosensory system. The latencies of the responses ranged from 5 to 50 ms. These results show that: somatosensory input can influence the activity of the vestibular apparatus at the most peripheral level; modulation of the afferent discharge is mediated by the efferent vestibular system (EVS); the influence of the EVS on the vestibular afferent activity is both inhibitory and facilitatory, and the responses to somatosensory stimulation are mediated by both long-latency polysynaptic and short-latency oligosynaptic pathways. The functional significance of these two pathways is discussed.

Animals↗
PubMed1982

Responses of afferent and efferent neurons to visual inputs in the vestibular nerve of the frog.

In the frog immobilized by intralymphatic injection of D-tubocurarine, stimulation of the visual apparatus with either electrical shocks applied to the optic chiasma or light pulses elicited, in many cases, an increase and a decrease of firing of efferent and afferent vestibular neurons, respectively, recorded from the horizontal semicircular canal nerve. Optokinetic stimulation was completely inefficient in modulating the efferent and afferent discharge. These results show that stimulation of the visual system can modify vestibular apparatus fuctioning at the most peripheral level. However, it is likely that the effects observed were due to an arousal phenomenon or/and to a motor corollary discharge.

Action Potentials↗
PubMed1982

Tonic influence from one labyrinth onto the contralateral one. An electrophysiological study in the frog.

In the frog's isolated head preparations, spontaneous activity was recorded from the whole nerve of the left horizontal semicircular canal (HC) for 6 min before and 16 min after destruction of the right labyrinth by heating or administration of d-tubocurarine (0.5 microliter, 5.10(-6)M) into the perilymph of the right labyrinth. Just after destruction on the right labyrinth, spontaneous activity of the left HC nerve abruptly increased by 20-400% in 24 preparations out of the 40 studied; activity then increased slowly and regularly and in most cases reached a steady level. In the 16 other preparations such destruction had no effect (15 preparations) or elicited a slight decrease of the HC nerve activity (one preparation). After curare administration, the spontaneous activity of the left HC nerve decreased by 20-100% in 27 preparations out of the 40 studied; in most cases such a decrease was reversed 25-80 min after administration of the drug. The spontaneous discharges were unaffected in 11 preparations and slightly increased in the two others. Destruction of the right labyrinth or administration of curare never modified spontaneous activity recorded from the left HC nerve when the connections between the two labyrinths had been interrupted either by sagittal section of the medulla oblongata or section of the right vestibular nerve close to the brain stem. These results demonstrate that one labyrinth has a tonic inhibitory influence on the contralateral one.

Animals↗
PubMed1977

Influence of the saccule, lagena and vertical posterior canal on the ipsilateral horizontal and vertical anterior semicircular canals in Rana esculenta: role of receptor-receptor fibres.

The influence of the efferent vestibular system being eliminated, the spontaneous activity of single afferent fibres of the ampullary nerves of the horizontal and vertical anterior semicircular canals was recorded in the frog. By stimulating electrically the nerves of the vertical posterior canal, lagena or saccule as well as by sectioning these nerves and then using statistical methods, it is shown that the receptor-receptor fibres arising from the above mentioned receptors have generally an inhibitory influence on the afferent activity from the horizontal and vertical anterior canals.

Animals↗
PubMed1976

Tonic influence of the efferent vestibular system on the spontaneous afferent activity from semicircular canals in the frog (Rana esculenta L.).

In the frog we have recorded the spontaneous activity of single afferent fibres of the ampullary nerves of the left horizontal semicircular canal (HC) and vertical anterior canal (VAC) in isolated head preparations. The recordings have been made in 4 experimental situations: intact preparations; preparations whose brain was destroyed; preparations whose contralateral vestibular nerve had been cut between Scarpa's ganglion and the brain; preparations where either an ampullary nerve (that of the HC or of the VAC) or the utricular nerve had been cut contralaterally. From our results, it appears that the efferent vestibular system has a tonic influence on the afferent activity from HC and VAC; the influence of the part of the efferent vestibular system (EVS) activity depending on contralateral vestibular inputs is inhibitory, while the influence of the part of the EVS activity depending on ipsilateral vestibular inputs might be facilitatory.

Animals↗
PubMed1976

[Action of vestibular receptors pn the spontaneous afferent activity of an ipsilateral semicircular canal in the frog].

In the frog, the influence of both the part of the efferent system which depends on ipsilateral vestibular inputs and the receptor-receptor fibre system on the afferent activity of semicircular canals is either null or facilitatory. The receptor-receptor fibre system being inhibitory, it seems that the part of the efferent vestibular activity which depends on ipsilateral vestibular inputs is facilitatory, which agrees with previous results.

Animals↗
PubMed1976

[Tonic conjugated action of receptor-receptor fibers and of the efferent vestibular system on the spontaneous afferene activity of a semicircular canal in the frog].

In the frog, the joint action of non-afferent vestibular systems [i.e. the efferent vestibular system and the receptor-receptor fibre system] on the afferent vestibular activity is null or very small. The receptor-receptor fibre system being inhibitory, it seems that the efferent vestibular system as a whole is facilitatory, which agrees with previous results.

Animals↗
PubMed1975

Influence of receptor-receptor fibres on the spontaneous afferent activity from semicircular canals in the frog (Rana esculenta).

The influence of the efferent vestibular system having been eliminated, the spontaneous activity of afferent fibres of the ampullary nerves of the horizontal and vertical anterior semicircular canals was recorded in the frog. By stimulating the ampullary nerve of one of these two canals while recording on the other, as well as by sectioning branches of the vestibular nerve and then using statistical methods, it is shown that receptor-receptor fibres have an inhibitory action on afferent activity from the horizontal and vertical anterior semicircular canals.

Animals↗