title: Perinatal exposure to androgen suppresses sexual dimorphism in nerve trunk diameter, axon number, and fiber size spectrum: a quantitative ultrastructural study of the adult rat mammary nerve.
abstract: The adult mammary nerves (MNs) from female, male, and testosterone-androgenized female rats were studied by light and electron microscopy. The female MNs trunk has twice the diameter of that of the male. Morphometry showed a significantly more myelinated (307 +/- 6) and unmyelinated axons (1654 +/- 10) in the female MN than the male MN (278 +/- 6 and 1373 +/- 28, respectively). Perinatal exposure of the female to testosterone significantly reduced the number of both axon types in the MN in adulthood (244 +/- 6 myelinated and 1300 +/- 32, unmyelinated). Another sexual dimorphism is a distinct group of large (>7.0 microm in diameter) myelinated axons known to conduct sensory information (i.e., touch and vibration). Because the male and the perinatally-androgenized female MNs lack these fibers, it is concluded that gonadal sex hormones may promote the differentiation of specific sets of axons committed to transmission of sensory cues relevant to reproduction.
authors.affiliation: Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-UAQ, Apartado Postal 1-1141, Zona Centro, Querétaro, CP 76001 Qro., Mexico.
authors.forename: Icnelia
authors.initials: I
authors.lastname: Huerta-Ocampo
authors.forename: Flavio
authors.initials: F
authors.lastname: Mena
authors.forename: Fernando
authors.initials: F
authors.lastname: Barrios
authors.forename: Gema
authors.initials: G
authors.lastname: Martínez
authors.forename: Leopoldo
authors.initials: L
authors.lastname: González
authors.forename: Jorge
authors.initials: J
authors.lastname: Larriva-Sahd
mesh_terms: D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D008297:Male; D008321:Mammary Glands, Animal / Q000294:innervation*; D046529:Microscopy, Electron, Transmission; D009412:Nerve Fibers / Q000187:drug effects* / Q000648:ultrastructure*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D013739:Testosterone / Q000494:pharmacology*; D014770:Virilism / Q000503:physiopathology
chemical_list: D000728:Androgens; D013739:Testosterone