title: An endocannabinoid system is localized to the hypophysial pars tuberalis of Syrian hamsters and responds to photoperiodic changes.
abstract: The hypophysial pars tuberalis (PT), an important interface between neuroendocrine brain centers (hypothalamus, pineal organ) and the pars distalis (PD) of the hypophysis, plays a central role in regulating seasonal reproduction and prolactin release. However, the signaling molecules that transmit photoperiodic information from the PT to the PD and control prolactin release (the so-called "tuberalins") have not yet been identified, despite an intense search for more than three decades. Here, we demonstrate an endocannabinoid system in the PT of the Syrian hamster, a photoperiodic species. By means of in situ hybrization, the PT was found to express N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), sn-1-selective diacylglycerol lipases (DAGLalpha and DAGLbeta), and monoacylglycerol lipase (MAGL), enzymes involved in endocannabinoid synthesis and degradation. The expression of NAPE-PLD, FAAH, and DAGLalpha was confirmed by immunohistochemistry. Expression and protein levels of DAGLs controlling the synthesis of 2-arachidonoyl glycerol (2-AG), a major endocannabinoid, were upregulated in the PT of Syrian hamsters kept under long-day conditions. Consequently, 2-AG levels were increased in the PT of these hamsters. A primary target of 2-AG, the cannabinoid receptor 1 (CB1), was expressed in the PD. Double-immunolabeling revealed that most of the CB1-immunoreactive cells in the PD were folliculostellate cells that were also immunoreactive for S-100 protein. Thus, the PT comprises an endocannabinoid system, and 2-AG may act as a photoperiodic messenger from the PT to the PD for the regulation of hypophysial hormonal secretion.
authors.affiliation: Dr. Senckenbergische Anatomie, Institut für Anatomie II, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Yasuo
authors.forename: Marco
authors.initials: M
authors.lastname: Koch
authors.forename: Helmut
authors.initials: H
authors.lastname: Schmidt
authors.forename: Simone
authors.initials: S
authors.lastname: Ziebell
authors.forename: Joerg
authors.initials: J
authors.lastname: Bojunga
authors.forename: Gerd
authors.initials: G
authors.lastname: Geisslinger
authors.forename: Horst-Werner
authors.initials: HW
authors.lastname: Korf
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D063385:Cannabinoid Receptor Modulators / Q000235:genetics* / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D063388:Endocannabinoids; D005989:Glycerides / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008647:Mesocricetus; D008994:Monoacylglycerol Lipases / Q000235:genetics / Q000378:metabolism; D009490:Neurosecretory Systems / Q000166:cytology / Q000378:metabolism*; D010740:Phospholipases / Q000235:genetics / Q000378:metabolism; D017440:Photoperiod; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism; D009418:S100 Proteins / Q000378:metabolism; D015290:Second Messenger Systems / Q000235:genetics; D015854:Up-Regulation / Q000502:physiology
chemical_list: D001095:Arachidonic Acids; D015415:Biomarkers; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D005989:Glycerides; D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D009418:S100 Proteins; C094503:glyceryl 2-arachidonate; D006867:Hydrolases; D010740:Phospholipases; D008994:Monoacylglycerol Lipases