title: An intrinsic CRF signaling system within the optic tectum.
abstract: Previous work indicates that CRF administration inhibits visually guided feeding in amphibians. We used the African clawed frog Xenopus laevis to examine the hypothesis that CRF acts as a neurotransmitter in the optic tectum, the major brain area integrating the visual and premotor pathways regulating visually guided feeding in anurans. Reverse transcriptase PCR revealed that cells in the optic tectum express mRNA for CRF and the CRF R1 receptor but not the CRF R2 receptor. Radioligand binding studies indicated that specific binding of [(125)I]-Tyr-oCRF to tectal cell membranes can be displaced by the CRF R1 antagonists antalarmin or NBI-27914. CRF increased the expression of mRNA encoding regulator of G-protein signaling 2 (rgs2) in tectal explants and this effect was blocked by antalarmin. CRF had no effect on basal glutamate or gamma-aminobutyric acid (GABA) secretion but inhibited secretion of norepinephrine from tectal explants, an effect that completely blocked by antalarmin. Using a homologous radioimmunoassay we determined that CRF release from tectal explants in vitro was potassium- and calcium-dependent. Basal and depolarization-induced CRF secretion was greater from optic tectum than hypothalamus/thalamus, telencephalon, or brainstem. We concluded that the optic tectum possesses a CRF signaling system that may be involved in modulating communication between sensory and motor pathways involved in food intake.
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA. james.carr@ttu.edu
authors.forename: James A
authors.initials: JA
authors.lastname: Carr
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Wenjie
authors.initials: W
authors.lastname: Li
authors.forename: Mamie
authors.initials: M
authors.lastname: Gao
authors.forename: Carlos
authors.initials: C
authors.lastname: Garcia
authors.forename: Jacob
authors.initials: J
authors.lastname: Lustgarten
authors.forename: Mike
authors.initials: M
authors.lastname: Wages
authors.forename: Ernest E
authors.initials: EE
authors.lastname: Smith
mesh_terms: D000818:Animals; D001001:Anura / Q000378:metabolism; D001066:Appetite / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D011743:Pyrimidines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013477:Superior Colliculi / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D011743:Pyrimidines; D011758:Pyrroles; D012333:RNA, Messenger; C103016:antalarmin