Learn More
Circadian rhythms of mammals are timed by an endogenous clock with a period of about 24 hours located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Light synchronizes this clock to the external environment by daily adjustments in the phase of the circadian oscillation. The mechanism has been thought to involve the release of excitatory amino(More)
Fifteen minutes of bright, white light exposure at midsubjective night resulted in a marked increase in both the number and stain density of c-fos protein (Fos)-immunoreactive neurons in the suprachiasmatic nuclei (SCN). In all cells, peroxidase reaction product was confined to the nucleus. Most Fos-immunoreactive cells were concentrated in the(More)
Syrian hamsters were fitted with guide cannulas stereotaxically aimed at the suprachiasmatic nuclei (SCN) and housed in constant darkness in cages equipped with running wheels. Animals received 300-nl injections of either vehicle, CNQX, or MK-801 into the region of the SCN 5 min before a brief (10 min at 20 lx) light exposure. Local administration of either(More)
The suprachiasmatic nucleus (SCN) contains the primary mammalian circadian clock. Light synchronizes these circadian rhythms through a mechanism involving the release of excitatory amino acids (EAA) and synthesis of nitric oxide (NO) in the SCN. In the current study, we investigated whether cGMP-mediated activation of cGMP-dependent protein kinase (PKG) is(More)
Converging lines of evidence have firmly established that the hypothalamic suprachiasmatic nucleus (SCN) is a light-entrainable circadian oscillator in mammals, critically important for the expression of behavioral and physiological circadian rhythms. Photic information essential for the daily phase resetting of the SCN circadian clock is conveyed directly(More)
Antibodies selective for the glutamate receptor subunits GluR1 and GluR2/3 were used to localize glutamate receptor immunoreactivity in the rat suprachiasmatic nuclei (SCN). These antisera identified two distinct cell populations within the SCN. Cells immunoreactive to GluR2/3 antiserum were located predominantly in the ventral SCN while antiserum selective(More)
We report the cloning and characterization of a novel serotonin receptor, designated as 5-HT7, which is coupled to the stimulation of adenylyl cyclase. 5-HT7 mRNA is expressed discretely throughout the CNS, predominantly in the thalamus and hypothalamus. 5-HT7 has a unique pharmacological profile that redefines agonist and antagonist classification of(More)
The suprachiasmatic nucleus (SCN) receives glutamatergic afferents from the retina and serotonergic afferents from the midbrain, and serotonin (5-HT) can modify the response of the SCN circadian oscillator to light. 5-HT1B receptor-mediated presynaptic inhibition has been proposed as one mechanism by which 5-HT modifies retinal input to the SCN (Pickard et(More)
In mammals, the suprachiasmatic nuclei (SCN) are the anatomical site of localization of the light-entrainable circadian clock responsible for the generation of daily rhythms in physiology and behavior. In addition to direct retinohypothalamic innervation, the SCN receive a prominent projection of fibers from the intergeniculate leaflet (IGL) of the(More)
Circadian rhythms in mammals are synchronized to environmental light-dark cycles through a direct retinal projection to the suprachiasmatic nucleus (SCN), a circadian clock. This process is thought to be modulated by other afferents to the SCN, including a dense serotonergic projection from the midbrain raphe. Previous work from this laboratory demonstrated(More)