Melatonin activates an outward current and inhibits Ih in rat suprachiasmatic nucleus neurons

Circadian Phase Shifts to Neuropeptide YIn Vitro: Cellular Communication and Signal Transduction

“…Interestingly, both N PY and serotonin phase shifts seem to depend on K ϩ channel activation (Prosser et al, 1994;Hall and Harrington, 1996; our unpublished results). Melatonin also phase shifts the circadian clock in the subjective day and seems to use PKC (McArthur et al, 1997); effects of melatonin on K ϩ channels, however, are observed only at concentrations well above those necessary for phase shifting (Jiang et al, 1995b).…”

International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, Classification, and Pharmacology of G Protein-Coupled Melatonin Receptors

“…MT 1 melatonin receptors expressed in X. laevis oocytes (Nelson et al, 1996) or AtT20 cells ) activate Kir3 inward-rectifier potassium channels through a PTX-sensitive mechanism that may involve ␤␥ subunits of G i proteins. Activation of Kir3 channels may underlie melatonin-mediated increases in potassium conductance (Jiang et al, 1995) and may be the mechanism by which melatonin inhibits neuronal firing in the SCN (Mason and Brooks, 1988;Shibata et al, 1989;Stehle et al, 1989). Hyperpolarization of neonatal pituitary cells may also be mediated by activation of MT 1 melatonin receptors (Vanecek and Klein, 1992).…”

Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters

“…Or perhaps the signalling mechanisms vary for different nonphotic cues. Nevertheless, nonphc~tic signal induction likely involves opening potassium (K' :) channels, thereby hyperpolarizing the cell and activating protein kinase C or protein kinase A cascades for NPY or 5HT, respectively Jiang et a/., 1995;Prosser et a/., 1994). Thus, nonphotic signal transduction appears to suppress activation of the SCN core, while photic signalling does the reverse.…”