The roles of luteinizing hormone-releasing hormone (LHRH) and serotonin (5HT) in the generation of gonadotropin and prolactin (PRL) surges were investigated in microdissected brain areas of proestrous (PRO), diestrous (DIE), and photoperiod-induced anestrous (PIA) Syrian hamster…
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The overall goal of these studies was to determine the nature of the signals used by circadian pacemaker located in the suprachiasmatic nucleus (SCN) to convey the time of day information to the rest of the organism. In these studies, we used the Syrian hamster as a model for in…
Circadian rhythms have been reported to change with age, and such changes are hypothesized to underlie changes in the timing of sleep-wake behavior and sleep disorders, problems which affect up to 40% of older people. Using an animal model, the Syrian hamster (Mesocricetus aurat…
Sleep in nursing home residents is highly fragmented. Disturbed circadian rhythms may be a partial cause. Melatonin, a pineal hormone, is a marker of circadian rhythms. Its secretion is synchronized by light. Nursing home residents are exposed to low levels of illumination. Ther…
Mammalian circadian rhythms in activity, gene expression, and pineal melatonin production are maintained by the suprachiasmatic nucleus (SCN), and are synchronized by light. One of the most abundant peptides in the brain, neuropeptide Y (NPY), has been shown to modulate circadia…
Circadian rhythms in the Syrian hamster can be adjusted by inducing the animal to become active during its usual sleep period. This type of clock resetting is distinct from clock resetting by light, and is thus known as nonphotic phase shifting. Although the prevailing view has …
Attention Deficit-Hyperactivity Disorder (ADHD) is the most commonly diagnosed behavioral disorder of childhood. Age-inappropriate daytime and nighttime locomotor overactivity and disturbed sleep have been well documented in ADHD. This study's objective was to examine the relati…
In Syrian hamsters, circadian rhythms can be phase shifted by light at night or by behavioural arousal during the day (usual sleep period). Previous work in this lab has defined arousal procedures that have differential clock resetting effects; arousal stimulated by running in a…
The circadian clock can be affected by a wide variety of drugs, hormones, and environmental conditions. For example, excessive alcohol intake may alter the normal phase (timing) of circadian rhythm, and may even abolish the expression of coherent circadian rhythms in human alcoh…
Day and night are often simulated for nocturnal rodents in the laboratory with 24 h lighting regimes alternating between moderate indoor light levels and complete darkness. Sometimes, complete darkness is replaced by dim illumination to aid human vision, with the assumption that…
Physiological and behavioral rhythms are generated by the suprachiasmatic nucleus (SCN). The SCN can be roughly divided into two regions, the core and the shell. Within the core and the shell, various cellular markers and neuropeptides integrate afferent photic and non-photic si…