Neuroscience and Neurobiology Commons^™

Day-Night Differences In Neural Activation In Histaminergic And Serotonergic Areas With Putative Projections To The Cerebrospinal Fluid In A Diurnal Brain, Alexandra Castillo-Ruiz, Andrew J. Gall, Laura Smale, Antonio A. Nunez

Faculty Publications

In nocturnal rodents, brain areas that promote wakefulness have a circadian pattern of neural activation that mirrors the sleep/wake cycle, with more neural activation during the active phase than during the rest phase. To investigate whether differences in temporal patterns of neural activity in wake-promoting regions contribute to differences in daily patterns of wakefulness between nocturnal and diurnal species, we assessed Fos expression patterns in the tuberomammillary (TMM), supramammillary (SUM), and raphe nuclei of male grass rats maintained in a 12:12 h light-dark cycle. Day-night profiles of Fos expression were observed in the ventral and dorsal TMM, in the SUM, …

Lesions Of The Intergeniculate Leaflet Lead To A Reorganization In Circadian Regulation And A Reversal In Masking Responses To Photic Stimuli In The Nile Grass Rat, Andrew J. Gall, Laura Smale, Lily Yan, Antonio A. Nunez

Faculty Publications

Light influences the daily patterning of behavior by entraining circadian rhythms and through its acute effects on activity levels (masking). Mechanisms of entrainment are quite similar across species, but masking can be very different. Specifically, in diurnal species, light generally increases locomotor activity (positive masking), and in nocturnal ones, it generally suppresses it (negative masking). The intergeniculate leaflet (IGL), a subdivision of the lateral geniculate complex, receives direct retinal input and is reciprocally connected with the primary circadian clock, the suprachiasmatic nucleus (SCN). Here, we evaluated the influence of the IGL on masking and the circadian system in a diurnal …

Distinct Retinohypothalamic Innervation Patterns Predict The Developmental Emergence Of Species-Typical Circadian Phase Preference In Nocturnal Norway Rats And Diurnal Nile Grass Rats, William D. Todd, Andrew J. Gall, Joshua A. Weiner, Mark S. Blumberg

Faculty Publications

How does the brain develop differently to support nocturnality in some mammals, but diurnality in others? To answer this question, one might look to the suprachiasmatic nucleus (SCN), which is entrained by light via the retinohypothalamic tract (RHT). However, because the SCN is more active during the day in all mammals studied thus far, it alone cannot determine circadian phase preference. In adult Norway rats (Rattus norvegicus), which are nocturnal, the RHT also projects to the ventral subparaventricular zone (vSPVZ), an adjacent region that expresses an in-phase pattern of SCN-vSPVZ neuronal activity. In contrast, in adult Nile grass rats (Arvicanthis …

Development Of Scn Connectivity And The Circadian Control Of Arousal: A Diminishing Role For Humoral Factors?, Andrew J. Gall, William D. Todd, Mark S. Blumberg

Faculty Publications

The suprachiasmatic nucleus (SCN) is part of a wake-promoting circuit comprising the dorsomedial hypothalamus (DMH) and locus coeruleus (LC). Although widely considered a "master clock," the SCN of adult rats is also sensitive to feedback regarding an animal's behavioral state. Interestingly, in rats at postnatal day (P)2, repeated arousing stimulation does not increase neural activation in the SCN, despite doing so in the LC and DMH. Here we show that, by P8, the SCN is activated by arousing stimulation and that selective destruction of LC terminals with DSP-4 blocks this activational effect. We next show that bidirectional projections among the …

Developmental Emergence Of Power-Law Wake Behavior Depends Upon The Functional Integrity Of The Locus Coeruleus, Andrew J. Gall, Badal Joshi, Janet Best, Virginia R. Florang, Jonathan A. Doorn, Mark S. Blumberg

Faculty Publications

STUDY OBJECTIVES:

Daily amounts of sleep and wakefulness are accumulated in discrete bouts that exhibit distinct statistical properties. In adult mammals, sleep bout durations follow an exponential distribution whereas wake bout durations follow a power-law distribution. In infant Norway rats, however, wake bouts initially follow an exponential distribution and only transition to a power-law distribution beginning around postnatal day 15 (P15). Here we test the hypothesis that the locus coeruleus (LC), one of several wake-active nuclei in the brainstem, contributes to this developmental transition.

DESIGN:

At P7, rats were injected subcutaneously with saline or DSP-4, a neurotoxin that targets noradrenergic …

The Development Of Day-Night Differences In Sleep And Wakefulness In Norway Rats And The Effect Of Bilateral Enucleation, Andrew J. Gall, William D. Todd, Baisali Ray, Cassandra M. Coleman, Mark S. Blumberg

Faculty Publications

The suprachiasmatic nucleus (SCN) exhibits circadian rhythmicity in fetal and infant rats, but little is known about the consequences of this rhythmicity for infant behavior. Here, in Experiment 1, we measured sleep and wakefulness in rats during the day and night in postnatal day (P)2, P8, P15 and P21 subjects. As early as P2, day-night differences in sleep-wake activity were detected. Nocturnal wakefulness began to emerge around P15 and was reliably expressed by P21. We hypothesized that the process of photic entrainment over the first postnatal week, which depends upon the development of connectivity between the retinohypothalamic tract (RHT) and …

Brainstem Cholinergic Modulation Of Muscle Tone In Infant Rats, Andrew J. Gall, Amy Poremba, Mark S. Blumberg

Faculty Publications

In week-old rats, lesions of the dorsolateral pontine tegmentum (DLPT) and nucleus pontis oralis (PnO) have opposing effects on nuchal muscle tone. Specifically, pups with DLPT lesions exhibit prolonged bouts of nuchal muscle atonia (indicative of sleep) and pups with PnO lesions exhibit prolonged bouts of high nuchal muscle tone (indicative of wakefulness). Here we test the hypothesis that nuchal muscle tone is modulated, at least in part, by cholinergically mediated interactions between these two regions. First, in unanesthetized pups, we found that chemical infusion of the cholinergic agonist carbachol (22 mM, 0.1 µL) within the DLPT produced high muscle …

Extraocular Muscle Activity, Rapid Eye Movements And The Development Of Active And Quiet Sleep, Adele M. H. Seelke, Andrew J. Gall, Karl Æ. Karlsson, Mark S. Blumberg

Faculty Publications

Rapid eye movements (REMs), traditionally measured using the electrooculogram (EOG), help to characterize active sleep in adults. In early infancy, however, they are not clearly expressed. Here we measured extraocular muscle activity in infant rats at 3 days of age (P3), P8 and P14-15 in order to assess the ontogeny of REMs and their relationship with other forms of sleep-related phasic activity. We found that the causal relationship between extraocular muscle twitches and REMs strengthened during the first two postnatal weeks, reflecting increased control of the extraocular muscles over eye movements. As early as P3, however, phasic bursts of extraocular …

The Neural Substrates Of Infant Sleep In Rats, Karl Æ. Karlsson, Andrew J. Gall, Ethan J. Mohns, Adele M. H. Seelke, Mark S. Blumberg

Faculty Publications

Sleep is a poorly understood behavior that predominates during infancy but is studied almost exclusively in adults. One perceived impediment to investigations of sleep early in ontogeny is the absence of state-dependent neocortical activity. Nonetheless, in infant rats, sleep is reliably characterized by the presence of tonic (i.e., muscle atonia) and phasic (i.e., myoclonic twitching) components; the neural circuitry underlying these components, however, is unknown. Recently, we described a medullary inhibitory area (MIA) in week-old rats that is necessary but not sufficient for the normal expression of atonia. Here we report that the infant MIA receives projections from areas containing …