Fos expression in arousal and reward areas of the brain in grass rats following induced wakefulness

Abstract

In the diurnal grass rat nocturnal voluntary wakefulness induces Fos expression in specific cellular populations of arousal and reward areas of the brain. Here, we evaluated whether involuntary wakefulness would result in similar patterns of Fos expression. We assessed this question using male grass rats that were sleep deprived for 6 h by gentle stimulation (SD group), starting 2 h before lights off (12:12 LD cycle). Then, we examined expression of Fos in cholinergic cells of the basal forebrain (BF), as well as in dopaminergic cells of the reward system, and compared these results to those obtained from an undisturbed control group. Different from previous results with grass rats that were voluntary awake, the BF of SD animals only showed a significant increase in Fos expression in non-cholinergic neurons of the medial septum (MS). These observations differ from reports for nocturnal rodents that are sleep deprived. Thus, our results show that voluntary and induced wakefulness have different effects on neural systems involved in wakefulness and reward, and that the effects of sleep deprivation are different across species. We also investigated whether other arousal promoting regions and circadian and stress related areas responded to sleep deprivation by changing the level of Fos expression. Among these areas, only the lateral hypothalamus (LH) and the ventro lateral preoptic area showed significant effects of sleep deprivation that dissipated after a 2 h period of sleep recovery, as it was also the case for the non-cholinergic MS. In addition, we found that Fos expression in the LH was robustly associated with Fos expression in other arousal and reward areas of the brain. This is consistent with the view that the arousal system of the LH modulates neural activity of other arousal regions of the brain, as described for nocturnal rodents.

Plastic oscillators and fixed rhythms: Changes in the phase of clock-gene rhythms in the PVN are not reflected in the phase of the melatonin rhythm of grass rats

“…Although species differences may be responsible for these divergent outcomes, these observations nevertheless support the view that voluntary reversals of the phase of activity (present study) affect the brain and the circadian system in a fashion that differs from the effects of forced-activity paradigms (Karatsoreos et al, 2011, McDonald et al, 2013, Saderi et al, 2013, Hsieh et al, 2014). In agreement with this view are the results of direct comparisons of the effects on the brain of spontaneous and forced wakefulness (Castillo-Ruiz et al, 2010, Castillo-Ruiz and Nunez, 2011). Thus, in grass rats, voluntary nocturnal wakefulness results in increased neuronal activation, as indicated by Fos expression, in reward areas of the brain (i.e., horizontal diagonal band, ventral tegmental area, and supramammillary nuclei; Castillo-Ruiz et al,2010), which is an observation not extended to studies using a forced-wakefulness paradigm with the same species (Castillo-Ruiz and Nunez, 2011) The NA grass rat appears to be an attractive model to understand the consequences of activity during the rest phase in a diurnal species, without the effects of the stress associated with forced-wakefulness paradigms (Castillo-Ruiz and Nunez, 2011).…”

Acute effects of light on the brain and behavior of diurnal Arvicanthis niloticus and nocturnal Mus musculus

“…Counts were done on two sections for the SCN, vSPZ, IGL, DLG, the ventrolateral preoptic nucleus (VLPO), the lateral hypothalamus (LH), locus coeruleus (LC) and DR. Counting boxes described in earlier reports were used to delineate regions sampled in the VLPO (190μm by 190μm; [65]), vSPZ (215μm by 160μm;[66]), LH (1200μm by 700μm; [67–68]), LC (400μm by 700μm; [69]), and DR (150μm by 650μm; [69]). The remaining regions were outlined and all labeled cells within their borders were mapped and counted.…”

Intergeniculate leaflet lesions result in differential activation of brain regions following the presentation of photic stimuli in Nile grass rats

“…Labeling of Fos-immunoreactive (Fos-ir) cells followed protocols previously established in the grass rat brain [18]. Sections were incubated in Fos antibody raised in rabbit (1:25,000, Santa Cruz Biotechnology, Santa Cruz, CA, USA) and processed with avidin-biotin-immunoperoxidase using DAB (3,3'-diaminobenzidine) as the chromogen enhanced with nickel sulfate.…”

“…Sections were examined under a light microscope (Leitz, Laborlux S, Wetzlar, Germany) equipped with a drawing tube to produce bilateral maps of Fos positive cells. Counting boxes were used to delineate the VLPO (190 μm × 190 μm; [19]), vSPVZ (215 μm × 160 μm; [20]), LC (400 μm × 700 μm; [18]), and DR (150 μm × 650 μm; [18]). The SCN, OPT, and DMH were outlined using thionin counterstained tissue.…”