Responses of brain and behavior to changing day-length in the diurnal grass rat (Arvicanthis niloticus)

Leach, Greg; Ramanathan, Chidambaram; Langel, Jennifer; Yan, Lili

doi:10.1016/j.neuroscience.2013.01.002

Cited by 29 publications

(48 citation statements)

References 47 publications

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“…Using the diurnal Nile grass rats, we and others have observed depression- and anxiety-like behaviors in winter-like lighting conditions, i.e. short photoperiods [4, 18] or daytime dim lighting [7, 17]. Furthermore, we found that hypothalamic neurons containing the neuropeptide orexin are likely to play a role in mediating the effects of light on mood and anxiety.…”

Section: Introductionsupporting

confidence: 51%

“…The number of TH-ir cells in the antagonist-treated group was comparable to those observed in DLD or SP animals. Furthermore, animals in these three comparable pro-depression conditions show increased depression-like behaviors compared to those in BLD group [4, 7, 17, 18]. The results indicate that the hypothalamic DA cells are related to the prevailing affective state.…”

Section: Discussionmentioning

confidence: 81%

“…Brains (n = 6/group) used in this experiment were obtained from two previous studies, in which animals were housed in either bright light: dark (BLD, 12:12 hr LD, 1000 lux/1 lux), dim light: dark (DLD, 12:12 hr LD, 50 lux/1 lux) or short photoperiod (SP, 8:16 hr LD, 1000 lux/1 lux) for 4 weeks [17, 18]. The animals were tested for depression-like behaviors during the light phase and then left undisturbed for at least 3 days before being sacrificed at the middle of the light phase (ZT6) for brain analysis.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Hypothalamic dopaminergic neurons in an animal model of seasonal affective disorder

Deats

Adidharma

Yan

2015

Neuroscience Letters

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Light has profound effects on mood regulation as exemplified in Seasonal Affective Disorder (SAD) and the therapeutic benefits of light therapy. However, the underlying neural pathways through which light regulates mood are not well understood. Our previous work has developed the diurnal grass rat, Arvicanthis niloticus, as an animal model of SAD. Following housing conditions of either 12:12hr Dim Light:Dark (DLD) or 8:16hr Short Photoperiod (SP), which mimic the lower light intensity or short day-length of winter, respectively, grass rats exhibit an increase in depression-like behavior compared to those housed in a 12:12hr Bright Light:Dark (BLD) condition. Furthermore, we revealed that the orexinergic system is involved in mediating the effects of light on mood and anxiety. To explore other potential neural substrates involved in the depressive phenotype, the present study examined hypothalamic dopaminergic (DA) and somatostatin (SST) neurons in the brains of grass rats housed in DLD, SP and BLD. Using immunostaining for tyrosine hydroxylase (TH) and SST, we found that the number of TH- and SST-ir cells in the hypothalamus was significantly lower in the DLD and SP groups compared to the BLD group. We also found that treating BLD animals with a selective orexin receptor 1 (OX1R) antagonist SB-334867 significantly reduced the number of hypothalamic TH-ir cells. The present study suggests that the hypothalamic DA neurons are sensitive to daytime light deficiency and are regulated by an orexinergic pathway. The results support the hypothesis that the orexinergic pathways mediate the effects of light on other neuronal systems that collectively contribute to light-dependent changes in the affective state.

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Section: Introductionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 81%

Section: Methodsmentioning

confidence: 99%

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Hypothalamic dopaminergic neurons in an animal model of seasonal affective disorder

Deats

Adidharma

Yan

2015

Neuroscience Letters

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“…One form of depression that is susceptible to changes in day length is seasonal affective disorder, which is at least partially based on photoperiodic alterations of the circadian system (26). A recent study using a day-active rodent model suggests a link between depressive-like behaviors and the photoperiodic responsiveness of the circadian clock (27). Although there is still insufficient evidence on the neurobiological mechanisms underlying seasonal affective disorder, altered GABAergic signaling in the SCN neuronal network should be considered a potential contributing factor.…”

Section: Discussionmentioning

confidence: 99%

Seasonal induction of GABAergic excitation in the central mammalian clock

Farajnia

Westering

Meijer

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

107

129

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The balance between excitation and inhibition is essential for the proper function of neuronal networks in the brain. The inhibitory neurotransmitter γ-aminobutyric acid (GABA) contributes to the network dynamics within the suprachiasmatic nucleus (SCN), which is involved in seasonal encoding. We investigated GABAergic activity and observed mainly inhibitory action in SCN neurons of mice exposed to a short-day photoperiod. Remarkably, the GABAergic activity in a long-day photoperiod shifts from inhibition toward excitation. The mechanistic basis for this appears to be a change in the equilibrium potential of GABA-evoked current. These results emphasize that environmental conditions can have substantial effects on the function of a key neurotransmitter in the central nervous system.S easonal changes in the photoperiod of the Earth's temperate zones affect the behavior and physiology of many organisms (1). The central circadian clock, located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus, can adapt to changes in day length and displays a compressed circadian pattern of electrical activity in short winter days and a decompressed pattern in long summer days (2). This pattern is based on a change in the phase distribution of the activity patterns of individual neurons, which becomes broad in the summer and narrow in the winter (3). The mechanisms that mediate and regulate photoperiod-induced phase distributions are currently not known.The neurotransmitter γ-aminobutyric acid (GABA) is believed to be involved in the phase adjustment and synchronization of the SCN neuronal network (4, 5). GABA and its receptors are expressed in most SCN neurons (6). GABAergic inhibition has been indicated to be important in normal physiological function within the brain. Alterations in this system (i.e., less inhibition) are shown to cause neurological disorders, such as epilepsy and autism (7,8). In addition to its classical inhibitory function within the SCN network, GABA has more recently been shown to also act as an excitatory transmitter, although its exact role is uncertain (4, 9-13). To understand the influence of photoperiod on GABAergic function, we studied synaptic activity, using patch clamp, and GABAergic responses, using Ca 2+ imaging techniques, in the SCN of mice adjusted to long-day and short-day photoperiods. We hypothesized that the narrow, synchronized phase distribution of active neurons during short-day photoperiods would result in increased synaptic activity during the day. Surprisingly, however, exposure to a short-day photoperiod decreased the frequency of spontaneous GABAergic synaptic events compared with the long-day photoperiod.Subsequently, we tested the effect of photoperiod on GABAinduced excitation in the SCN neuronal network. Ca 2+ transients were measured in response to GABA stimulation in long-day and short-day photoperiods. Interestingly, of all cells from the long-day photoperiod, 40% were excitatory and 36% were inhibitory. In contrast, in the short-day photoperiod, 28% of the c...

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“…Four weeks of a 12 h/12 h light/dark cycle under dim illumination conditions (50 lux/1 lux) attenuated indices of serotonin signaling in the dorsal raphe nucleus in grass rats (A. niloticus) [34]. Three weeks of a short photoperiod (8 h/16 h light/dark cycle) induced lower brain levels of serotonin and its precursor l-tryptophan in C57BL/6J mice [35].…”

Section: Rhythms Of Plasma Levels Of Corticosterone Melatonin and Nmentioning

confidence: 95%

Short photoperiod condition increases susceptibility to stress in adolescent male rats

Liu

Yuan

et al. 2016

Behavioural Brain Research

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Responses of brain and behavior to changing day-length in the diurnal grass rat (Arvicanthis niloticus)

Cited by 29 publications

References 47 publications

Hypothalamic dopaminergic neurons in an animal model of seasonal affective disorder

Hypothalamic dopaminergic neurons in an animal model of seasonal affective disorder

Seasonal induction of GABAergic excitation in the central mammalian clock

Short photoperiod condition increases susceptibility to stress in adolescent male rats

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