title: Neurotrophin-3 is a target-derived neurotrophic factor for penile erection-inducing neurons.
abstract: The aim of this study was to determine whether the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin (NT)-3 could act as endogenous target-derived trophic factors for erection-inducing, i.e. penis-projecting major pelvic ganglion (MPG) neurons, and/or penile sensory neurons in adult rat. This was accomplished by studying the expression of NT mRNAs in the penis and their cognate receptors in the MPG and dorsal root ganglia (DRGs), and the retrograde axonal transport of radioiodinated NTs injected into the corpora cavernosa. Northern hybridization showed that NGF, BDNF, and NT-3 mRNAs are expressed in the shaft of the penis. In situ hybridization combined with usage of the retrograde tracer Fluoro-Gold showed that TrkC and p75 receptors are expressed in penis-projecting neurons of the MPG whereas the mRNAs for TrkA and TrkB receptors were undetectable. However, all the NT receptor mRNAs were expressed in penile sensory neurons of sacral level 1 (S1) DRG. (125)I-NT-3 injected into the shaft of the penis was retrogradely transported into the MPG and S1 DRG, whereas radioiodinated NGF and BDNF were transported specifically into the S1 DRG, thus confirming the existence of functional NT receptors in these penile neurons. In conclusion, these data suggest that NT-3 may act as a target-derived neurotrophic factor for both erection-inducing and penile sensory neurons, whereas NGF and BDNF may be more important for the sensory innervation of the penis.
authors.affiliation: Institute of Biotechnology, P.O. Box 56, Viikki Biocenter, FIN-00014 University of Helsinki, Helsinki, Finland. jukka.hiltunen@helsinki.fi
authors.forename: J O
authors.initials: JO
authors.lastname: Hiltunen
authors.forename: A
authors.initials: A
authors.lastname: Laurikainen
authors.forename: E
authors.initials: E
authors.lastname: Klinge
authors.forename: M
authors.initials: M
authors.lastname: Saarma
mesh_terms: D000818:Animals; D001345:Autoradiography; D015152:Blotting, Northern; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis / Q000493:pharmacokinetics / Q000502:physiology; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D005456:Fluorescent Dyes; D005727:Ganglia, Spinal / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D007457:Iodine Radioisotopes; D008297:Male; D009414:Nerve Growth Factors / Q000096:biosynthesis / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D020933:Neurotrophin 3 / Q000096:biosynthesis / Q000502:physiology*; D010410:Penile Erection / Q000502:physiology*; D010413:Penis / Q000294:innervation* / Q000502:physiology*; D018075:RNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D019275:Radiopharmaceuticals; D051381:Rats; D017208:Rats, Wistar; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology; D020800:Receptor, Nerve Growth Factor / Q000502:physiology; D013266:Stilbamidines
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D019208:Brain-Derived Neurotrophic Factor; D018076:DNA, Complementary; D005456:Fluorescent Dyes; D007457:Iodine Radioisotopes; D009414:Nerve Growth Factors; D020933:Neurotrophin 3; D018075:RNA, Complementary; D012333:RNA, Messenger; D019275:Radiopharmaceuticals; D020800:Receptor, Nerve Growth Factor; D013266:Stilbamidines; D020794:Receptor Protein-Tyrosine Kinases