title: Pressure hyperalgesia in hind limb suspended rats.
abstract: BACKGROUND
  Spaceflight and simulated microgravity often associate with pain and prediabetes. Streptozotocin (STZ)-induced moderate insulinopenia rat models of prediabetes result in pressure hyperalgesia. The current study was designed to determine whether or not simulated microgravity induced by hind limb suspension (HLS) in rats lead to insulinopenia and pressure hyperalgesia.
  
  
  METHODS
  Adult male rats were divided into HLS (N = 20) and control, non-suspended (N = 16) groups, respectively. Bodyweight and hind limb pressure-pain withdrawal threshold (PPT) were measured at regular 2-5 d intervals for 7 d before and 12-13 d after HLS.
  
  
  RESULTS
  Bodyweights and PPT of control and HLS animals measured on the day of suspension were not different. During the experiment, control rats gained 61 +/- 5 g, but maintained their PPT at the baseline level. Suspended rats gained 26 +/- 3 g of weight during the same time period and their PPT declined from 105 +/- 6 g to 84 +/- 6 g. Neither blood glucose nor pancreatic islet density and area were affected by HLS. However, the random plasma insulin of HLS rats was significantly lower than that of control animals (1.6 +/- 0.2 vs. 2.7 +/- 0.2 ng ml(-1)).
  
  
  CONCLUSIONS
  The observed relationship between insulin and PPT levels in the HLS rats was similar to that observed in rats with STZ-induced insulinopenia. These data suggest that moderate insulinopenia may affect the rat's sensitivity to deep pressure directly, without affecting glucose homeostasis. In addition, our data suggest that HLS rats may develop peripheral neuropathy.
authors.affiliation: Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Parimal
authors.initials: P
authors.lastname: Chowdhury
authors.forename: Michael E
authors.initials: ME
authors.lastname: Soulsby
authors.forename: John
authors.initials: J
authors.lastname: Jayroe
authors.forename: Nisreen S
authors.initials: NS
authors.lastname: Akel
authors.forename: Dana
authors.initials: D
authors.lastname: Gaddy
authors.forename: Maxim
authors.initials: M
authors.lastname: Dobretsov
mesh_terms: D000818:Animals; D019417:Hindlimb Suspension; D006930:Hyperalgesia / Q000209:etiology*; D007328:Insulin / Q000097:blood*; D007515:Islets of Langerhans / Q000473:pathology; D016014:Linear Models; D008297:Male; D017288:Pain Threshold; D011312:Pressure / Q000009:adverse effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007328:Insulin