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Serotonergic potentiation of dark pulse‐induced phase‐shifting effects at midday in hamsters
Author(s) -
Mendoza Jorge,
Clesse Daniel,
Pévet Paul,
Challet Etienne
Publication year - 2008
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2008.05493.x
Subject(s) - per1 , circadian rhythm , serotonergic , clock , endocrinology , medicine , suprachiasmatic nucleus , agonist , raphe nuclei , light effects on circadian rhythm , antagonist , melatonin , 8 oh dpat , circadian clock , serotonin , neuroscience , chemistry , biology , receptor
In mammals, resetting of the suprachiasmatic clock (SCN) by behavioral activation or serotonin (5‐HT) agonists is mimicked by dark pulses, presented during subjective day in constant light (LL). Because behavioral resetting may be mediated in part by 5‐HT inputs to the SCN, here we determined whether 5‐HT system can modulate dark‐induced phase‐shifts in Syrian hamsters housed in LL. Two hours of darkness at mid‐subjective day (circadian time 6; CT‐6) resulted in increased concentrations of 5‐HT in the SCN tissue and induction of c‐FOS expression in the raphe nuclei. Injections of the 5‐HT 1A/7 agonist (+)8‐OH‐DPAT or dark pulses at CT‐6 induced phase‐advances of the wheel‐running activity rhythm and down‐regulated the expression of the clock genes Per1‐2 and c‐FOS in the SCN in a similar way. The combination of both treatments [(+)8‐OH‐DPAT + dark pulses], however, resulted in larger phase‐advances, while associated molecular changes were not significantly modified, except for the gene Dbp , in comparison to (+)8‐OH‐DPAT or dark pulses alone. Dark resetting was blocked by pre‐treatment with a 5‐HT 7 antagonist, but not with a 5‐HT 1A antagonist. The additive phase‐shifts of two different cues to reset the SCN clock open wide the gateway for non‐photic shifting, leading to new strategies in chronotherapy.