Pharmacological aspects of excitatory synaptic transmission to second‐order vestibular neurons in the frog

Cochran, S.L.; Kasik, P.; Precht, W.

doi:10.1002/syn.890010114

Cited by 231 publications

(46 citation statements)

References 57 publications

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“…6 B 2 ) consisted of a disynaptic slow EPSP after electrical stimulation of the entire contralateral N.VIII (see above) ( Fig. 6B 3 ), compatible with previous in vivo and in vitro (Cochran et al, 1987) studies. However, electrical activation of individual contralateral semicircular canal nerve branches revealed a more specific organization.…”

Section: Synaptic Organization Of the Canal Commissural Inhibitionsupporting

confidence: 68%

“…The vestibular commissural excitation is most likely mediated by glutamate that activates contralateral vestibular neurons through both AMPA and NMDA receptors as shown previously in the isolated frog brain (Cochran et al, 1987;Knöpfel, 1987). The relative contributions of AMPA and NMDA components to the commissural EPSPs varied between the different studies and depended on the Mg 2ϩ concentration in the bath.…”

Section: Pharmacological Profile Of Semicircular Canal Commissural Inmentioning

confidence: 85%

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Functional Organization of Vestibular Commissural Connections in Frog

Malinvaud¹,

Vassias²,

Reichenberger³

et al. 2010

J. Neurosci.

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Central vestibular neurons receive substantial inputs from the contralateral labyrinth through inhibitory and excitatory brainstem commissural pathways. The functional organization of these pathways was studied by a multi-methodological approach in isolated frog whole brains. Retrogradely labeled vestibular commissural neurons were primarily located in the superior vestibular nucleus in rhombomeres 2/3 and the medial and descending vestibular nucleus in rhombomeres 5-7. Restricted projections to contralateral vestibular areas, without collaterals to other classical vestibular targets, indicate that vestibular commissural neurons form a feedforward pushpull circuitry. Electrical stimulation of the contralateral coplanar semicircular canal nerve evoked in canal-related second-order vestibular neurons (2°VN) commissural IPSPs (ϳ70%) and EPSPs (ϳ30%) with mainly (ϳ70%) disynaptic onset latencies. The dynamics of commissural responses to electrical pulse trains suggests mediation predominantly by tonic vestibular neurons that activate in all tonic 2°VN large-amplitude IPSPs with a reversal potential of Ϫ74 mV. In contrast, phasic 2°VN exhibited either nonreversible, smallamplitude IPSPs (ϳ40%) of likely dendritic origin or large-amplitude commissural EPSPs (ϳ60%). IPSPs with disynaptic onset latencies were exclusively GABAergic (mainly GABA A receptor-mediated) but not glycinergic, compatible with the presence of GABAimmunopositive (ϳ20%) and the absence of glycine-immunopositive vestibular commissural neurons. In contrast, IPSPs with longer, oligosynaptic onset latencies were GABAergic and glycinergic, indicating that both pharmacological types of local inhibitory neurons were activated by excitatory commissural fibers. Conservation of major morpho-physiological and pharmacological features of the vestibular commissural pathway suggests that this phylogenetically old circuitry plays an essential role for the processing of bilateral angular head acceleration signals in vertebrates.

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Section: Synaptic Organization Of the Canal Commissural Inhibitionsupporting

confidence: 68%

Section: Pharmacological Profile Of Semicircular Canal Commissural Inmentioning

confidence: 85%

Functional Organization of Vestibular Commissural Connections in Frog

Malinvaud¹,

Vassias²,

Reichenberger³

et al. 2010

J. Neurosci.

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“…The government of Oberbayern (211-2531-31/95) granted permission for these experiments. As described in previous studies (Cochran et al 1987;Straka and Dieringer 1993), the animals were deeply anesthetized with 0.1% 3-aminobenzoic acid ethyl ester (MS-222) and perfused transcardially with iced Ringer solution [which contained (in mM) 75 NaCl, 25 NaHCO 3 , 2 CaCl 2 , 2 KCl, 0.5 mM MgCl 2 , and 11 glucose; pH 7.4). Thereafter, the skull and the bony labyrinth were opened by a ventral approach.…”

Section: E T H O D Smentioning

confidence: 99%

Second-Order Vestibular Neurons Form Separate Populations With Different Membrane and Discharge Properties

Straka

Beraneck²,

Rohregger³

et al. 2004

Journal of Neurophysiology

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Straka, H., M. Beraneck, M. Rohregger, L. E. Moore, P.-P, Vidal, and N. Vibert. Second-order vestibular neurons form separate populations with different membrane and discharge properties. J Neurophysiol 92: 845-861, 2004. First published March 24, 2004 10.1152/ jn.00107.2004. Membrane and discharge properties were determined in second-order vestibular neurons (2°VN) in the isolated brain of grass frogs. 2°VN were identified by monosynaptic excitatory postsynaptic potentials after separate electrical stimulation of the utricular nerve, the lagenar nerve, or individual semicircular canal nerves. 2°VN were classified as vestibulo-ocular or -spinal neurons by the presence of antidromic spikes evoked by electrical stimulation of the spinal cord or the oculomotor nuclei. Differences in passive membrane properties, spike shape, and discharge pattern in response to current steps and ramp-like currents allowed a differentiation of frog 2°VN into two separate, nonoverlapping types of vestibular neurons. A larger subgroup of 2°VN (78%) was characterized by brief, high-frequency bursts of up to five spikes and the absence of a subsequent continuous discharge in response to positive current steps. In contrast, the smaller subgroup of 2°VN (22%) exhibited a continuous discharge with moderate adaptation in response to positive current steps. The differences in the evoked spike discharge pattern were paralleled by differences in passive membrane properties and spike shapes. Despite these differences in membrane properties, both types, i.e., phasic and tonic 2°VN, occupied similar anatomical locations and displayed similar afferent and efferent connectivities. Differences in response dynamics of the two types of 2°VN match those of their pre-and postsynaptic neurons. The existence of distinct populations of 2°VN that differ in response dynamics but not in the spatial organization of their afferent inputs and efferent connectivity to motor targets suggests that frog 2°VN form one part of parallel vestibulomotor pathways.

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“…Permission for these experiments was granted by Regierung von Oberbayern (211-2531-31/95). As described in previous studies (Cochran et al 1987;Straka and Dieringer 1993), the animals were deeply anesthetized (0.1% 3-aminobenzoic acid ethyl ester; MS-222) and perfused transcardially with iced Ringer solution [containing (in mM) 75 NaCl, 25 NaHCO 3 , 2 CaCl 2 , 2 KCl, 0.1 MgCl 2 , and 11 glucose; pH 7.4]. Thereafter, the skull and the bony labyrinth were opened by a ventral approach.…”

Section: E T H O D Smentioning

confidence: 99%

Patterns of Canal and Otolith Afferent Input Convergence in Frog Second-Order Vestibular Neurons

Straka

Holler

Goto

2002

Journal of Neurophysiology

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Straka, H., S. Holler, and F. Goto. Patterns of canal and otolith afferent input convergence in frog second-order vestibular neurons. J Neurophysiol 88: 2287-2301, 2002 10.1152/jn.00370.2002 were identified in the isolated frog brain by the presence of monosynaptic excitatory postsynaptic potentials (EPSPs) after separate electrical stimulation of individual vestibular nerve branches. Combinations of one macular and the three semicircular canal nerve branches or combinations of two macular nerve branches were stimulated separately in different sets of experiments. Monosynaptic EPSPs evoked from the utricle or from the lagena converged with monosynaptic EPSPs from one of the three semicircular canal organs in ϳ30% of 2°VN. Utricular afferent signals converged predominantly with horizontal canal afferent signals (74%), and lagenar afferent signals converged with anterior vertical (63%) or posterior vertical (37%) but not with horizontal canal afferent signals. This convergence pattern correlates with the coactivation of particular combinations of canal and otolith organs during natural head movements. A convergence of afferent saccular and canal signals was restricted to very few 2°VN (3%). In contrast to the considerable number of 2°VN that received an afferent input from the utricle or the lagena as well as from one of the three canal nerves (ϳ30%), smaller numbers of 2°VN (14% of each type of 2°otolith or 2°canal neuron) received an afferent input from only one particular otolith organ or from only one particular semicircular canal organ. Even fewer 2°VN received an afferent input from more than one semicircular canal or from more than one otolith nerve (ϳ7% each). Among 2°VN with afferent inputs from more than one otolith nerve, an afferent saccular nerve input was particularly rare (4 -5%). The restricted convergence of afferent saccular inputs with other afferent otolith or canal inputs as well as the termination pattern of saccular afferent fibers are compatible with a substrate vibration sensitivity of this otolith organ in frog. The ascending and/or descending projections of identified 2°VN were determined by the presence of antidromic spikes. 2°VN mediating afferent utricular and/or semicircular canal nerve signals had ascending and/or descending axons. 2°VN mediating afferent lagenar or saccular nerve signals had descending but no ascending axons. The latter result is consistent with the absence of short-latency macular signals on extraocular motoneurons during vertical linear acceleration. Comparison of data from frog and cat demonstrated the presence of a similar organization pattern of maculo-and canal-ocular reflexes in both species. I N T R O D U C T I O NComponents of linear and angular head acceleration are detected separately by the different otolith and semicircular canal organs in the labyrinth. These signals are mediated in parallel pathways by afferent nerve fibers to the vestibular nuclei, the brain stem reticular formation, and the cerebellum. Afferent nerve fibers from individual semicirc...

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Pharmacological aspects of excitatory synaptic transmission to second‐order vestibular neurons in the frog

Cited by 231 publications

References 57 publications

Functional Organization of Vestibular Commissural Connections in Frog

Functional Organization of Vestibular Commissural Connections in Frog

Second-Order Vestibular Neurons Form Separate Populations With Different Membrane and Discharge Properties

Patterns of Canal and Otolith Afferent Input Convergence in Frog Second-Order Vestibular Neurons

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