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  • 1
    Electronic Resource
    Electronic Resource
    Unilateral ablation of the frontal eye field of the rat affects the beating field of ocular nystagmus (1994)
    Springer
    Experimental brain research 98 (1994), S. 391-400 
    Details
    ISSN: 1432-1106
    Keywords: Optokinetic nystagmus ; Vestibulo-ocular reflex ; Frontal eye field ; Hemineglect ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous saccadic orientation and compensatory eye movements in response to optokinetic and vestibular velocity steps were studied in head-restrained, pigmented rats before and 1–2 weeks after unilateral ablation of the frontal eye field (FEF). One group of rats (n=5) received a deep lesion and another group of rats (n=4) received a superficial lesion of the left FEF. Postoperative response parameters such as the duration of slow buildup of eye velocity, the steady state velocity gain, the duration of optokinetic afternystagmus and of per- and postrotatory vestibular nystagmus were similar in the two groups of rats and did not differ from preoperative values measured in the same individuals. Superimposed upon these velocity components of nystagmus was a transient orienting response that expressed itself by a shift of the beating field of nystagmus in quick phase direction (gaze shift). The amplitudes of this gaze shift in quick phase direction were asymmetric in rats with a deep FEF lesion. Gaze shift amplitudes toward the side of the lesion were significantly enhanced and gaze shift amplitudes toward the intact side were significantly reduced. Similar asymmetries were observed in the distribution of spontaneous orienting movements of these rats in the light. Spontaneous saccadic eye movements of the same animals in darkness, however, were symmetric in amplitude to either side. These deficits suggest a partial sensory hemineglect after a deep unilateral lesion of the FEF and an involvement of this structure in the selective attention for targets in visual space. Thus the FEF orients the gaze at rest by means of saccades toward points of interest and during simulated circular locomotion by means of a shift of the beating field of nystagmus toward the visual sector that will be approached next.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233977
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  • 2
    Electronic Resource
    Electronic Resource
    GABA-activated Chloride Currents of Postnatal Mouse Retinal Ganglion Cells are Blocked by Acetylcholine and Acetylcarnitine: How Specific are Ion Channels in Immature Neurons? (1994)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 6 (1994), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The goal of this study was to clarify pharmacological properties of GABAA receptors in cells of the mouse retinal ganglion cell layer in situ. Spontaneous synaptic currents and responses to exogenous GABA were recorded from individual neurons in retinal whole mounts (postnatal days 1–3) or retinal stripe preparations (postnatal days 4–6). Drugs were applied by a fast local superfusion system. Current responses were measured with the patch-clamp technique in the whole-cell configuration. All cells responded to exogenous GABA (average EC50 and Hill coefficient: 16.7 μM and 0.95 respectively) and generated GABAergic synaptic currents in response to elevated KCI. GABA-induced currents of retinal ganglion cells were blocked by bicuculline, picrotoxin and Zn2+, as well as strychnine, and increased by pentobarbital, clonazepam and 3α-hydroxy-5α-pregnan-20-one. In some retinal ganglion cells GABA caused an increase in the frequency of spontaneous synaptic currents, which points to a partially depolarizing action of this traditionally inhibitory neurotransmitter in the neural retina. Our major observation is that acetylcholine and acetylcarnitine blocked or reduced GABAergic inhibitory postsynaptic currents and responses to exogenous GABA. This effect was seen in only a fraction of retinal ganglion cells and occurred in both the undesensitized and the desensitized state of the GABAA receptor. The block was voltage-independent and persisted during coapplication with the nicotinic and muscarinic acetylcholine receptor antagonists D-tubocurarine and atropine. In contrast to GABA-activated Cl− currents, glycine-activated Ch currents remained unaffected by acetylcholine and acetylcarnitine. Acetylcarnitine had no effect on voltage-activated Ca2+ channel currents and glutamate-activated currents. Similar results were obtained in a dissociated cell culture preparation from the neonatal rat superior colliculus. In these cells acetylcholine induced a rightward shift in the dose - response curve for GABA. Taken together, these results indicate that acetylcholine and acetylcarnitine can act directly at the GABAA binding site and thereby reduce the action of GABA in the immature retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1994.tb00606.x
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    Paper (German National Licenses)
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