Pinealectomy Reduces Optic Nerve But Not Intergeniculate Leaflet Input to the Suprachiasmatic Nucleus at Night

González, Joaquín; Dyball, R. E. J.

doi:10.1111/j.1365-2826.2005.01395.x

Cited by 4 publications

(11 citation statements)

References 68 publications

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“…All experiments were carried out in accordance with the Animals (Scientific Procedures) Act (UK) 1986. For experiments in pinealectomised animals, pinealectomy was performed as described by Gonzalez and Dyball (13) at least 21 days before recording.…”

Section: Methodsmentioning

confidence: 99%

Daily Rhythms of Spike Coding in the Rat Supraoptic Nucleus

Bhumbra

Lombardelli

Gonzalez

et al. 2009

J Neuroendocrinology

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Novel measures of coding based on interspike intervals were used to characterise the rhythms of single unit activity in the supraoptic nucleus during the day/night cycle in urethane-anaesthetised rats in vivo. Both continuously firing and phasic cells showed significant (P < 0.001) diurnal rhythms of spike frequency and in the irregularity of firing, as quantified by the log interval entropy (ENT). Comparison of rhythms in log interval ENT showed that the amplitude of the rhythms was greater for the continuously firing cells than for the phasic cells (P = 0.002). Rhythms persisted after hypertonic stimulation or pinealectomy and both treatments reduced the amplitude significantly only for the continuously firing cell group. By contrast, the mesor (i.e. mid-point of the rhythm) was reduced only for the phasic cell group. A similar analysis applied to the activity of cells of the suprachiasmatic nucleus showed that, after pinealectomy, there was a significant rhythm in ENT (P < 0.001) but not firing rate; however, the amplitude of the rhythm in ENT was attenuated (P = 0.047). Diurnal changes in the electrical activity of supraoptic cells are consistent with previously reported circadian changes in magnocellular neuropeptide release. Differences between continuous and phasic cell groups in the effects of osmotic stimulation on rhythmic activity indicate that the two cell types differ in their coding of osmolality and zeitgeber time information. The different effects of pinealectomy on the supraoptic and suprachiasmatic nuclei suggest that removal of endogenous melatonin unmasks a difference in circadian coding between the two nuclei.

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Section: Methodsmentioning

confidence: 99%

Daily Rhythms of Spike Coding in the Rat Supraoptic Nucleus

Bhumbra

Lombardelli

Gonzalez

et al. 2009

J Neuroendocrinology

Self Cite

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“…In line with data obtained following in vivo stimulation of the IGL/vLGN (Roig et al . ; González & Dyball, ), we found that single pulse stimulation of the GHT could evoke either inhibitory (Fig. B ) or excitatory responses (Fig.…”

Section: Resultsmentioning

confidence: 58%

“…These values represent the time to peak response rather than response onset (which is not always easy to accurately assess for inhibitory responses) and are equivalent those reported by previous in vivo studies (Roig et al . ; González & Dyball, ).…”

Section: Resultsmentioning

confidence: 99%

Geniculohypothalamic GABAergic projections gate suprachiasmatic nucleus responses to retinal input

Hanna

Walmsley

Pienaar

et al. 2017

The Journal of Physiology

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Sensory input to the master mammalian circadian clock, the suprachiasmatic nucleus (SCN), is vital in allowing animals to optimize physiology and behaviour alongside daily changes in the environment. Retinal inputs encoding changes in external illumination provide the principle source of such information. The SCN also receives input from other retinorecipient brain regions, primarily via the geniculohypothalamic tract (GHT), although the contribution of these indirect projections to circadian photoreception is currently poorly understood. To address this deficit, in the present study, we established an in vitro mouse brain slice preparation that retains connectivity across the extended circadian system. Using multi-electrode recordings, we first confirm that this preparation retains intact optic projections to the SCN, thalamus and pretectum and a functional GHT. We next show that optogenetic activation of GHT neurons selectively suppresses SCN responses to retinal input, and also that this effect exhibits a pronounced day/night variation and involves a GABAergic mechanism. This inhibitory action was not associated with overt circadian rhythmicity in GHT output, indicating modulation at the SCN level. Finally, we use in vivo electrophysiological recordings alongside pharmacological inactivation or optogenetic excitation to show that GHT signalling actively modulates specific features of the SCN light response, indicating that GHT cells are primarily activated by crossed retinal projections. Taken together, our data establish a new model for studying network communication in the extended circadian system and provide novel insight into the roles of GHT-signalling, revealing a mechanism by which thalamic activity can help gate retinal input to the SCN according to time of day.

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“…Both the retinohypothalamic and IGL pathways terminate in the SCN. However, a significantly greater number of neurons respond to the IGL than to photic stimulation from the retinohypothalamic tract [25, 26]. The greater representation of IGL sensitive neurons underlines the importance of the nonphotic entrainment of circadian rhythms.…”

Section: Intergeniculate Leaflet and Suprachiasmatic Nucleimentioning

confidence: 99%

The role of the thalamus in sleep, pineal melatonin production, and circadian rhythm sleep disorders

Jan

Reíter²,

Wasdell

et al. 2008

Journal of Pineal Research

175

120

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Borbely [1] introduced theories of how circadian and homeostatic mechanisms influence sleep, which, subsequently, have been widely accepted. Sleep-wake cycles are controlled by circadian rhythm oscillators in the suprachiasmatic nuclei (SCN). In contrast, the homeostatic process regulates sleep need (propensity) which increases during the day and decreases during sleep depending on the amount of mainly nonrapid eye movement sleep (NREM) a person previously had [2]. The homeostatic mechanisms are able to overrule the circadian system because sleep deprivation leads to longer sleep. Adenosine is one of the main sleepinducing factors in homeostasis [3], although there are also changes in neuronal activities associated with sleep propensity [4].Over time, researchers have been increasingly able to explain various aspects of sleep, but the neurological basis of these highly complex mechanisms had remained unclear. Within this framework of circadian rhythms and homeostasis, the photic input into the SCN and the functions of these small structures responsible for circadian rhythms were strongly emphasized. However, the role of SCN, especially when it was viewed in isolation without their extensive neurological and neurochemical network, failed to explain the pathophysiology of circadian rhythm sleep disorders (CRSD).In recent years, research into the anatomic and physiological aspects of circadian rhythmicity has blossomed. Major progress has been made in understanding molecular biology of the SCN [5] and at the same time, knowledge about the roles of the thalamus and other brain structures in sleep have expanded [6][7][8][9][10][11]. Sleep is a neurological function and the process of wakefulness and sleep involves the entire central nervous system. Similarly, modulators of melatonin secretion and the effects of this indoleamine are more complex than previously thought. Melatonin receptors, clock genes, sleep deprivation, the timing of circadian rhythms, a vast number of neurochemicals, hormones, the environment, and various neurological structures and other factors are acting as a symphony to influence melatonin physiology and the sleep-wake cycle [2,5,[12][13][14]. The role of thalamus in sleepThe thalamus plays a critical role in processing, integrating, correlating, and relaying sensory and motor information [9]. Major auditory, visual, and somatosensory pathways, together with inputs from the limbic structures, the brainstem, and cerebellum have their final subcortical relays in this highly complex paired structure, which Abstract: The thalamus has a strong nonphotic influence on sleep, circadian rhythmicity, pineal melatonin production, and secretion. The opening of the sleep gate for nonrapid eye movement sleep is a thalamic function but it is assisted by melatonin which acts by promoting spindle formation. Thus, melatonin has a modulatory influence on sleep onset and maintenance. A remarkable similarity exists between spindle behavior, circadian rhythmicity, and pineal melatonin production throughout life. To...

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Pinealectomy Reduces Optic Nerve But Not Intergeniculate Leaflet Input to the Suprachiasmatic Nucleus at Night

Cited by 4 publications

References 68 publications

Daily Rhythms of Spike Coding in the Rat Supraoptic Nucleus

Daily Rhythms of Spike Coding in the Rat Supraoptic Nucleus

Geniculohypothalamic GABAergic projections gate suprachiasmatic nucleus responses to retinal input

The role of the thalamus in sleep, pineal melatonin production, and circadian rhythm sleep disorders

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