title: Single prenatal injections of melatonin or the D1-dopamine receptor agonist SKF 38393 to pregnant hamsters sets the offsprings' circadian rhythms to phases 180 degrees apart.
abstract: Pregnant Syrian hamsters with lesions of the suprachiasmatic nucleus (SCN) received single injections of melatonin or the D1-dopamine receptor agonist, SKF 38393 on day 15 of gestation (1 day before birth). Pups were weaned on postnatal day 20 and their freerunning activity rhythms recorded for 3-4 weeks. The pups' phases on the day of weaning were significantly clustered in both of the treatment groups, but the average phases differed by approximately 180 degrees. The results demonstrate that a single prenatal stimulus is sufficient to set the phases of the hamsters' rhythms and that the phase established depends on the stimulus. Both c-fos mRNA and Fos protein were expressed in the fetal SCN after SKF 38393 injection but neither were expressed after melatonin injection. Simulations showed that a single stimulus could produce the observed synchrony from a population of uniformally distributed phases if the phase shifts were three to four times the magnitude of the adult hamster light phase response curve (PRC). A light pulse PRC mimicked the effect of an SKF 38393 injection and a dark-pulse PRC mimicked the effects of a melatonin injection. Together these results suggest that dopamine and melatonin either are, or mimic, maternal entraining signals that represent day and night.
authors.affiliation: Department of Biology, Northeastern University, Boston, MA 02115, USA. nviswana@lynx.neu.edu
authors.forename: N
authors.initials: N
authors.lastname: Viswanathan
authors.forename: F C
authors.initials: FC
authors.lastname: Davis
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology*; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D006224:Cricetinae; D005260:Female; D008550:Melatonin / Q000494:pharmacology*; D011247:Pregnancy
chemical_list: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D008550:Melatonin