Wyniki wyszukiwania

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Ipsilateral retinal innervation of oscillatory olivary pretectal nucleus neurons - is it important?

100%

Orlowska P., Szkudlarek H. J., Sikorska A., Lewandowski M. H.

Acta Neurobiologiae Experimentalis

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2011

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tom 71

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nr S

The olivary pretectal nucleus (OPN), suprachiasmatic nucleus and the intergeniculate leaflet of the thalamus, play a crucial role in the entrainment of circadian rhythms. All mentioned nuclei receive input from the retina - the only source of information about environmental light in mammals. It is known that rod/cone- and melanopsin-mediated photoreception are needed to display proper responses of circadian pacemaker to light stimuli. Our previous studies described population of OPN cells which fire in an oscillatory mode with a period of about 2 min. This rhythmic firing pattern requires intact excitatory input from the retina. We have shown that blockade of contralateral rod/ cone photoreception caused a decrease in firing rate of OPN cells without influencing their rhythmic activity. However, inhibition of contralateral melanopsin photoreception showed 3 types of neuronal responses: complete disappearance (n=5), temporary disturbances (n=5) and no changes (n=2) in oscillatory pattern of OPN cells. To clarify the likelihood that persistence of oscillatory pattern in 2 of the cases is caused by ipsilateral retinal innervation, we performed in vivo experiments on Wistar rats combining electrophysiology with intraocular injections. Contralateral eye was injected with glutamatergic receptor antagonists or 2-aminoethoxydiphenylborane to inhibit rodcone or melanopsin phototransduction respectively. Tetrodotoxin was used to suppress ipsilateral retinal activity. The results have shown that simultaneous blockade of melanopsin phototransduction and ipsilateral retinal activity strongly decreased firing rate of oscillatory cells (10.63 ± 2.81 to 2.60 ± 2.19 Hz) and caused disappearance of their rhythmic spiking. Interestingly, vanishing of the rhythm was temporary in 3 out of 7 cases and recovered oscillations were longer (95.93 ± 30.11 to 128.33 ± 48.31 s). We suggest that ipsilateral retinal innervation may play a role in the oscillatory activity of some OPN cells.

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Melanopsin-based photoreception: contribution to the mechanism of generation of infraslow rhythm in the rat olivary pretectal nucleus

100%

Orlowska P., Tokarczyk E., Szkudlarek H., Lewandowski M.

Acta Neurobiologiae Experimentalis

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2009

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tom 69

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nr 3

In mammals, environmental light signals are captured by the eye’s photoreceptors: rods, cones and intrinsically photosensitive melanopsin retinal ganglion cells (ipRGCs). During the last few years, ipRGCs were extensively studied and their membrane properties, projections and physiological role in regulation of circadian rhythms and pupillary light refl ex were documented. However, these studies do not explain how activity of ipRGCs affects physiology of target cells in suprachiasmatic nuclei (SCN), intergeniculate leafl et (IGL) or olivary pretectal nucleus (OPN). Some of the neurons constituting above mentioned structures, express slow oscillatory activities that are modulated by light and depend on functional input from the retina. This implicates, that mechanism of expression of slow oscillation may include synaptic drive from ipRGCs. Recently, 2-aminoethoxydiphenylborane (2-APB) was described as an acute inhibitor of ipRGCs activity. This study combines intravitreous injections of 2-APB with extracellular recordings from oscillatory OPN neurons in urethane anesthetized Wistar rat. The experiments showed that inactivation of ipRGCs activity abolish oscillatory pattern and reduce fi ring rate of OPN neurons. Injection of comparable volume of physiological saline in control experiments had no effect on oscillatory activity. To our knowledge, this is the fi rst study that directly links extraretinal neuronal fi ring with activity of ipRGCs.

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Melanopsin modulation of slow oscillatory activity in the subcortical visual system

76%

Orlowska P., Allen A. E., Brown T. M., Storchi R., Szkudlarek H. J., Lucas R. J., Lewandowski M. H.

Acta Neurobiologiae Experimentalis

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2013

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tom 73

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nr Suppl.1

Slow oscillatory activity (SOA) has been described in several structures of the subcortical visual system, including the olivary pretectal nucleus (OPN) and lateral geniculate nucleus (LGN). Since rhythmic spiking in the OPN is dependent on contralateral retinal output, we set out to investigate whether rod-cone and/or melanopsin photoreceptors are important for SOA generation in the OPN and LGN. Two different approaches were used: extracellular single-unit recordings in rats combined with intraviteral injections of photoreceptor blockers, and extracellular multi-electrode recordings from wild-type or genetically modified mice, lacking either melanopsin (Opn4-/-) or rods and cones (rd/rd cl). The first of these methods indicated a major contribution of melanopsin to SOA generation, since this was abolished in the OPN after intravitreal 2-APB injection. This melanopsin contribution was confirmed by the second approach, with Opn4-/- mice having the lowest percentage of oscillatory cells and also the shortest average period in both structures. This is the first study to show SOA in the mouse visual system and to characterize its retinal origins, revealing melanopsin expressing retinal ganglion cells as the main driving force underlying this activity.

Ograniczanie wyników

3 Acta Neurobiologiae Experimentalis

3 Orlowska P.

2 Lewandowski M. H.

2 Szkudlarek H. J.

1 Allen A. E.

1 Brown T. M.

1 Lewandowski M.

1 Lucas R. J.

1 Sikorska A.

1 Storchi R.

1 Szkudlarek H.

1 Tokarczyk E.

1 2013

1 2011

1 2009

Ipsilateral retinal innervation of oscillatory olivary pretectal nucleus neurons - is it important?

Melanopsin-based photoreception: contribution to the mechanism of generation of infraslow rhythm in the rat olivary pretectal nucleus

Melanopsin modulation of slow oscillatory activity in the subcortical visual system