title: Association of chronic diabetes and hypertension in sural nerve morphometry: an experimental study.
abstract: BACKGROUND
  Prospective studies have shown incidence rates of hypertension in diabetes mellitus to be three times that of subjects without diabetes mellitus. The reverse also applies, with the incidence of diabetes two to three times higher in patients with hypertension. Despite this common clinical association, the contribution of each isolated entity in the development of a neuropathy is still not well understood. The aims of the present study were to investigate the presence of peripheral neuropathy in spontaneously hypertensive rats (SHR) and SHR with chronically induced diabetes, using a morphological and morphometric study of the sural nerves.
  
  
  METHODS
  Female SHR and normotensive Wistar rats (WR), 8 weeks old, received a single intravenous injection of streptozotocin (STZ) through the tail vein. Controls from both strains received vehicle. Twelve weeks after the injection, sural nerves were dissected and prepared for light microscopy. Morphometry of sural nerve fascicles and myelinated fibers was performed with the aid of computer software.
  
  
  RESULTS
  The sural nerve myelinated fibers were highly affected by experimental diabetes in normotensive rats, causing mainly the reduction of the fiber size. Hypertensive rats showed characteristics of small fiber neuropathy and a severe reduction of the number and density or Schwann cells. The association between diabetes and hypertension caused an increase on the average size of the myelinated fibers, pointing to a small fiber loss, associated to axonal atrophy.
  
  
  CONCLUSIONS
  Our study gives morphological support to the existence of a neuropathy due to hypertension, which is among one of the most common risk factors for diabetic neuropathy. The association between the two neuropathies showed to be a complex alteration, involving and including both, large and small fibers neuropathy. Hypertension caused, indeed, an exacerbation of the alterations already observed in experimental models of diabetic neuropathy.
authors.affiliation: Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil.
authors.forename: Luciana Sayuri
authors.initials: LS
authors.lastname: Sanada
authors.affiliation: Department of Anatomy, José do Rosário Velano University, Alfenas, MG Brazil.
authors.forename: Marcelo Rodrigo
authors.initials: MR
authors.lastname: Tavares
authors.affiliation: Departament of Physical Therapy, Federal University of Sergipe, Aracaju, SE Brazil.
authors.forename: Karina Laurenti
authors.initials: KL
authors.lastname: Sato
authors.affiliation: Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil.
authors.forename: Renata da Silva
authors.initials: Rda S
authors.lastname: Ferreira
authors.affiliation: Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil.
authors.forename: Milena Cardoso Maia
authors.initials: MC
authors.lastname: Neubern
authors.affiliation: Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil.
authors.forename: Jaci Ayrton
authors.initials: JA
authors.lastname: Castania
authors.affiliation: Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil.
authors.forename: Helio Cesar
authors.initials: HC
authors.lastname: Salgado
authors.affiliation: Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil ; Department of Surgery and Anatomy, School of Medicine of Ribeirão Preto, USP, Av. Bandeirantes 3900, Ribeirão Preto, SP Brazil.
authors.forename: Valéria Paula Sassoli
authors.initials: VP
authors.lastname: Fazan
keywords: Experimental diabetes; Experimental hypertension; Morphometry; Myelinated fibers; Spontaneously hypertensive rats; Streptozotocin; Sural nerve