title: Peripheral fields of sympathetic vasoconstrictor neurons in guinea pigs.
abstract: We have combined retrograde axonal tracing using Fast Blue and Dil, with immunohistochemistry, to estimate the maximum size of peripheral fields of identified sympathetic vasoconstrictor neurons projecting to guinea-pig ear tips. Many neurons in the superior cervical ganglia were labelled with both Fast Blue and Dil after dye injections up to 7 mm apart. Few neurons were labelled when dye injections were 8-10 mm apart. Neurons labelled with both Dil and Fast Blue after dye injections 5-7 mm apart had, on average, larger somata (436 +/- 84 microm2, mean +/- SEM, n = 47) than neurons labelled with Dil only (388 +/- 11 microm2, n = 147). Typically, 50-100 neurons innervated a region of vasculature 1 mm in diameter. We conclude that sympathetic vasoconstrictor neurons branch widely before converging on to their target blood vessels. Progressive recruitment of vasoconstrictor neurons with increasing field size would provide an efficient mechanism for graded neural control of the circulation.
authors.affiliation: Department of Anatomy and Histology, Flinders University of South Australia, Adelaide, Australia. ian.gibbins@flinders.edu.au
authors.forename: I L
authors.initials: IL
authors.lastname: Gibbins
authors.forename: B
authors.initials: B
authors.lastname: Hoffmann
authors.forename: J L
authors.initials: JL
authors.lastname: Morris
mesh_terms: D000578:Amidines; D000818:Animals; D001158:Arteries / Q000294:innervation / Q000502:physiology; D002232:Carbocyanines; D004423:Ear; D005260:Female; D005456:Fluorescent Dyes; D006168:Guinea Pigs; D007124:Immunoenzyme Techniques; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009478:Neuropeptide Y / Q000378:metabolism; D012867:Skin / Q000098:blood supply* / Q000294:innervation; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000502:physiology; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*
chemical_list: D000578:Amidines; D002232:Carbocyanines; D005456:Fluorescent Dyes; D009478:Neuropeptide Y; C031455:diamidino compound 253-50