NMDA receptors are involved in temporal integration in the oculomotor system of the cat

Mettens, Philippe; Chéron, Guy; Godaux, Emile

doi:10.1097/00001756-199406270-00009

Cited by 7 publications

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“…The fact that the PHN has reciprocal connections with the MVN (McCrea & Baker, 1985; McCrea, 1988) indicates that, in addition to the intraconnections and interconnections of the PHN, reciprocal connections between the PHN and MVN are important for neural integrator (Fukushima & Kaneko, 1995; Moschovakis, 1997). The importance of synaptic organization via NMDA receptors in the PHN was demonstrated in early studies by injection of ketamine or APV into the PHN of alert cats (Cheron et al ., 1992; Mettens et al ., 1994). In addition, the importance of cholinergic inputs (Navarro‐López et al ., 2004, 2005; Márquez‐Ruiz et al ., 2007) in PHN function was also identified.…”

Section: Discussionmentioning

confidence: 99%

Membrane properties of excitatory and inhibitory neurons in the rat prepositus hypoglossi nucleus

Shino

Ozawa

Furuya

et al. 2008

Eur J of Neuroscience

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The prepositus hypoglossi nucleus (PHN) is thought to be a neural structure involved in transforming eye or head velocity signals into eye position signals for horizontal eye movements. In this study, we investigated the relationship between electrophysiological membrane properties and expression patterns of cellular markers for excitatory and inhibitory neurons by whole-cell patch clamp recordings followed by reverse transcription polymerase chain reaction (RT-PCR) analysis in rat brainstem slices. Three types of voltage response properties, namely afterhyperpolarization (AHP), firing pattern, and response to hyperpolarizing current pulses, were characterized in each neuron. Following RT-PCR analysis, we identified PHN neurons as either glutamatergic (n = 22) or GABAergic (n = 43), although a small number of cholinergic (n = 2) and glycinergic neurons (n = 1) were also identified. Both glutamatergic and GABAergic neurons showed a wide variety of membrane properties; however, we found several characteristic relationships between neuronal type and membrane properties. Most neurons exhibiting (i) AHP without a slow component, (ii) a firing pattern with a delay in the generation of the first spike, (iii) a firing pattern with a transient burst and (iv) a firing pattern with a prolonged initial interspike interval were GABAergic. On the other hand, glutamatergic neurons were primarily characterized by a low firing rate. These results indicate that there is a close relationship between specific electrophysiological membrane properties and expression of chemical markers in some types of glutamatergic and GABAergic PHN neurons.

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Section: Discussionmentioning

confidence: 99%

Membrane properties of excitatory and inhibitory neurons in the rat prepositus hypoglossi nucleus

Shino

Ozawa

Furuya

et al. 2008

Eur J of Neuroscience

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“…The consequences of local blockade in the PH nucleus of either excitatory or inhibitory neurotransmitter receptors have been previously reported by various investigators. Blockade of NMDA, kainate or AMPA glutamatergic receptors in monkeys (Arnold et al 1999) and cats (Mettens et al 1994 a ) produced spontaneous eye movement alterations similar to those described in the present study, except for NBQX, which did not affect eye position signals in cats (Mettens et al 1994 a ). However, the results obtained following pharmacological modification of the inhibitory neurotransmission systems reveal a large variability, which makes it difficult to understand comprehensively how neurotransmitters work in the generation of velocity and position signals in the PH nucleus.…”

Section: Discussionmentioning

confidence: 99%

“…Drug injections in the PH nucleus produced nystagmus with either straight or curved slow phases separated by quick resetting movements. The significance of these two types of eye movement alteration has been well established (Cannon & Robinson, 1987; Godaux et al 1993; Mettens et al 1994 a, b, c ; Godaux & Cheron, 1996; Moreno‐López et al 1998). Velocity imbalance, such as that produced when the tonic inputs from both vestibular nuclei are not identical, produces nystagmus with straight slow phases.…”

Section: Methodsmentioning

confidence: 99%

Nitric oxide facilitates GABAergic neurotransmission in the cat oculomotor system: a physiological mechanism in eye movement control

Moreno‐López

Escudero

Estrada

2002

The Journal of Physiology

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Nitric oxide (NO) synthesis by prepositus hypoglossi (PH) neurons is necessary for the normal performance of horizontal eye movements. We have previously shown that unilateral injections of NO synthase (NOS) inhibitors into the PH nucleus of alert cats produce velocity imbalance without alteration of the eye position control, both during spontaneous eye movements and the vestibulo‐ocular reflex (VOR). This NO effect is exerted on the dorsal PH neuropil, whose fibres increase their cGMP content when stimulated by NO. In an attempt to determine whether NO acts by modulation of a specific neurotransmission system, we have now compared the oculomotor effects of NOS inhibition with those produced by local blockade of glutamatergic, GABAergic or glycinergic receptors in the PH nucleus of alert cats. Both glutamatergic antagonists used, 2‐amino‐5‐phosphonovaleric acid (APV) and 2,3‐dihydro‐6‐nitro‐7‐sulphamoyl‐benzo quinoxaline (NBQX), induced a nystagmus contralateral to that observed upon NOS inhibition, and caused exponential eye position drift. In contrast, bicuculline and strychnine induced eye velocity alterations similar to those produced by NOS inhibitors, suggesting that NO oculomotor effects were due to facilitation of some inhibitory input to the PH nucleus. To investigate the anatomical location of the putative NO target neurons, the retrograde tracer Fast Blue was injected in one PH nucleus, and the brainstem sections containing Fast Blue‐positive neurons were stained with double immunohistochemistry for NO‐sensitive cGMP and glutamic acid decarboxylase. GABAergic neurons projecting to the PH nucleus and containing NO‐sensitive cGMP were found almost exclusively in the ipsilateral medial vestibular nucleus and marginal zone. The results suggest that the nitrergic PH neurons control their own firing rate by a NO‐mediated facilitation of GABAergic afferents from the ipsilateral medial vestibular nucleus. This self‐control mechanism could play an important role in the maintenance of the vestibular balance necessary to generate a stable and adequate eye position signal.

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“…Although no animal model for APN exists, basic studies of neural integrator function might produce data to support or refute our hypothesis. Specifically, the technique of pharmacological inactivation of the neural integrator by microinjecting drugs with known effects on neurotransmitter systems in NPH‐MVN has been studied 44‐48. Agents with agonist or antagonist actions at gamma‐aminobutyric acid (GABA), glutamate, and kainate receptors all cause gaze‐evoked nystagmus with centripetal eye drifts, implying that the neural integrator had been made “leaky” (decreased time constant of integration).…”

Section: An Example Of Nystagmus For Which There Is No Animal Model Bmentioning

confidence: 99%

A Neurobiological Approach to Acquired Nystagmus

Leigh

Das

Seidman

2002

Annals of the New York Academy of Sciences

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The development of animal and mathematical models for several forms of acquired nystagmus has led to more comprehensive knowledge of these disorders. In the best understood forms, such as periodic alternating nystagmus, our range of knowledge includes an animal model, the neurotransmitters involved, and effective treatment. For some other forms, such as downbeat nystagmus, we have an animal model, but reliable treatment is lacking. In other cases, exemplified by acquired pendular nystagmus, we have only a provisional hypothesis for pathogenesis to account for the oscillations, without an animal model, but effective treatment is possible in some patients. The present trend of studying all aspects of the neurobiology of nystagmus, from molecules to behavior, seems to be the best approach to extend our knowledge and to identify new treatments, but much remains to be done.

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NMDA receptors are involved in temporal integration in the oculomotor system of the cat

Cited by 7 publications

References 0 publications

Membrane properties of excitatory and inhibitory neurons in the rat prepositus hypoglossi nucleus

Membrane properties of excitatory and inhibitory neurons in the rat prepositus hypoglossi nucleus

Nitric oxide facilitates GABAergic neurotransmission in the cat oculomotor system: a physiological mechanism in eye movement control

A Neurobiological Approach to Acquired Nystagmus

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