title: Anatomical and functional characterization of clock gene expression in neuroendocrine dopaminergic neurons.
abstract: Oscillations of gene expression and physiological activity in suprachiasmatic nucleus (SCN) neurons result from autoregulatory feedback loops of circadian clock gene transcription factors. In the present experiment, we have determined the pattern of PERIOD1 (PER1), PERIOD2 (PER2), and CLOCK expression within neuroendocrine dopaminergic (DAergic) neurons (NDNs) of ovariectomized (OVX) rats. We have also determined the effects of per1, per2, and clock mRNA knockdown in the SCN with antisense deoxyoligonucleotides (AS-ODN) on DA release from NDNs. Diurnal rhythms of PER1 and PER2 expression in tuberoinfundibular DAergic (TIDA) and periventricular hypophyseal DAergic (PHDA) neurons, peaked at circadian time (CT)18 and CT12, respectively. Rhythms of PER1 expression in tuberhypophyseal neuroendocrine DAergic (THDA) neurons were undetectable. Rhythms of PER2 expression were found in all three populations of NDNs, with greater levels of PER2 expression between CT6 and CT12. AS-ODN injections differentially affected DA turnover in the axon terminals of the median eminence (ME), neural lobe (NL) and intermediate lobe (IL) of the pituitary gland, resulting in a significant decrease in DA release in the early subjective night in the ME (TIDA), a significant increase in DA release at the beginning of the day in the IL (PHDA), and no effect in the NL (THDA). AS-ODN-treatment induced a rhythm of DA concentration in the anterior lobe, with greater DA levels in the middle of the day. These data suggest that clock gene expression, particularly PER1 and PER2, within NDNs may act to modulate diurnal rhythms of DA release from NDNs in the OVX rat.
authors.affiliation: Department of Biological Science, Florida State Univ., Tallahassee, Florida, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Sellix
authors.forename: Marcel
authors.initials: M
authors.lastname: Egli
authors.forename: Maristela O
authors.initials: MO
authors.lastname: Poletini
authors.forename: De'Nise T
authors.initials: DT
authors.lastname: McKee
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Bosworth
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Fitch
authors.forename: Marc E
authors.initials: ME
authors.lastname: Freeman
mesh_terms: D056930:ARNTL Transcription Factors; D000818:Animals; D030801:Animals, Genetically Modified; D016375:Antisense Elements (Genetics); D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D003345:Corticosterone / Q000378:metabolism; D003463:Cues; D004327:Drinking Behavior / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D020644:Midline Thalamic Nuclei / Q000378:metabolism; D009474:Neurons / Q000502:physiology*; D009490:Neurosecretory Systems / Q000033:anatomy & histology* / Q000166:cytology / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics; D010052:Ovariectomy; D056950:Period Circadian Proteins; D011388:Prolactin / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013493:Suprachiasmatic Nucleus / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics
chemical_list: D056930:ARNTL Transcription Factors; D016375:Antisense Elements (Genetics); D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D003345:Corticosterone; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D011388:Prolactin; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; C538961:Bmal1 protein, mouse; C539023:Per1 protein, mouse; C539024:Per1 protein, rat; C513312:Per2 protein, mouse; C513311:Per2 protein, rat; C538944:Clock protein, mouse; C538945:Clock protein, rat