title: Associating high intensity and modulated frequency of TENS delays analgesic tolerance in rats.
abstract: BACKGROUND
  Transcutaneous electrical nerve stimulation (TENS) is a non-invasive analgesic resource extensively used in painful conditions. However, preclinical studies suggest that the prolonged use of TENS results in the development of tolerance to its analgesic effect. The present study investigated the analgesic effect and development of tolerance to TENS with four different stimulation protocols.
  
  
  METHODS
  Male Wistar rats induced with joint inflammation were divided into four groups: sensory intensity, low motor intensity, high motor intensity and sham groups. TENS was applied daily for 20 min with alternating frequency between 4 and 100 Hz until tolerance development was evidenced. Mechanical hyperalgesia was measured before and after each TENS daily application.
  
  
  RESULTS
  After TENS, tolerance was evidenced There was a significant reduction in the mechanical withdrawal threshold in all groups 24 h after induction of inflammation (p  <  0.01). We observed a loss of analgesic efficacy of TENS around the 12th, 19th and 19th days in the groups treated with sensory intensity, low motor intensity and high motor intensity, respectively (p < 0.02) when analysed using paired measurements and compared with the control.
  
  
  CONCLUSIONS
  The association between frequency variation and intensity at motor level promotes a delay in the development of analgesic tolerance to TENS, optimizing and extending its therapeutic effectiveness.
authors.affiliation: Departamento de Fisioterapia, Universidade Federal de Sergipe, Aracaju, Brazil; Programa de Pós-Graduação em Ciências da Saúde, Universidade Federal de Sergipe, Aracaju, Brazil.
authors.forename: L V
authors.initials: LV
authors.lastname: Lima
authors.forename: K M L
authors.initials: KM
authors.lastname: Cruz
authors.forename: T S S
authors.initials: TS
authors.lastname: Abner
authors.forename: C M D
authors.initials: CM
authors.lastname: Mota
authors.forename: M E J
authors.initials: ME
authors.lastname: Agripino
authors.forename: V J
authors.initials: VJ
authors.lastname: Santana-Filho
authors.forename: J M
authors.initials: JM
authors.lastname: DeSantana
mesh_terms: D000818:Animals; D018771:Arthralgia / Q000209:etiology / Q000628:therapy*; D001169:Arthritis, Experimental / Q000150:complications; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000628:therapy*; D008297:Male; D017288:Pain Threshold / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D004561:Transcutaneous Electric Nerve Stimulation