Melatonin generates an outward potassium current in rat suprachiasmatic nucleus neurones in vitro independent of their circadian rhythm
UNSPECIFIED. (2001) Melatonin generates an outward potassium current in rat suprachiasmatic nucleus neurones in vitro independent of their circadian rhythm. NEUROSCIENCE, 107 (1). pp. 99-108. ISSN 0306-4522Full text not available from this repository.
The present study investigated the membrane mechanisms underlying the inhibitory influence of melatonin on suprachiasmatic nucleus (SCN) neurotics in a hypothalamic slice preparation, Perforated-patch recordings were performed to prevent the rapid rundown of spontaneous firing rate as observed during whole cell recordings and to preserve circadian rhythmicity in SCN neurones. In current-clamp mode melatonin (1 muM or 1 nM) application, in the presence of agents that block action potential generation and fast synaptic transmission, resulted in a membrane hyperpolarisation accompanied with a decrease in input resistance in the majority of SCN neurotics (71-86%). The amplitude or the hyperpolarisation was not found to be significantly different between circadian time 5-12 and 14-21. In voltage-clamp mode melatonin (1 muM or 1 nM) induced an outward current accompanied with an increase in membrane conductance. The current was found to be mainly potassium driven with voltage kinetics resembling those of an open rectifying potassium conductance. Investigations into the signal transduction mechanism revealed melatonin-induced inhibition of SCN neurotics to be sensitive to pertussis toxin but independent of intracellular cAMP levels and phospholipase C activity.
The present study shows that melatonin, at night-time physiological concentrations, reduces the neuronal excitability of the majority of SCN neurones independent of the time of application in the circadian cycle. Thus in vivo melatonin may be important for circadian time-keeping by amplifying the circadian rhythm in SCN neurones, by lowering their sensitivity to phase-shifting stimuli occurring at night, (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.
|Item Type:||Journal Article|
|Subjects:||R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry|
|Journal or Publication Title:||NEUROSCIENCE|
|Publisher:||PERGAMON-ELSEVIER SCIENCE LTD|
|Number of Pages:||10|
|Page Range:||pp. 99-108|
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