title: Neurotropin®inhibits calpain activity upregulated by specific alternation of rhythm in temperature in the mesencephalon of rats.
abstract: OBJECTIVE
  Neurotropin® (NTP), an analgesic for chronic pain, has antihyperalgesic effects in specific alternation of rhythm in temperature (SART)-stressed rats. Previous studies have shown that SART stress induces hyperalgesia, as well as post-translational modification of proteins (including substrates for calpain, a calcium-dependent cysteine protease) in the mesencephalon of rats. To better understand the mechanism of action of NTP, we investigated whether SART stress activates calpain in the mesencephalon of rats and whether NTP inhibits this activation.
  
  
  METHODS
  Wistar rats were exposed to SART stress for 5days. NTP (200NU/kg/day) was administered intraperitoneally every day from the onset of SART stress. The mechanical pain threshold was measured using the Randall-Selitto test on the 6th day. Thereafter, the rat mesencephalon was immediately collected and calpain activity was examined using western blot analysis with a calpain cleavage site-specific antibody.
  
  
  RESULTS
  SART stress induced hyperalgesia and increased the calpain activity in the mesencephalon of rats. In contrast, NTP treatment attenuated the hyperalgesia and prevented the increase in calpain activity in the mesencephalon of SART-stressed rats. Interestingly, a negative correlation was identified between calpain activity and mechanical pain threshold in SART-stressed rats treated with or without NTP. Furthermore, NTP inhibited calpain activity on mammalian uncoordinated-18 in rat mesencephalon homogenate and Ac-LLY-AFC as substrates in an in vitro cell-free system.
  
  
  CONCLUSIONS
  Our data demonstrate that NTP treatment prevents SART stress-induced calpain activation in the mesencephalon of rats and suggests that NTP-mediated antihyperalgesia is associated with an inhibition of calpain activity in the mesencephalon.
authors.affiliation: Department of Pharmacological Research, Institute of Bio-Active Science, Nippon Zoki Pharmaceutical Co., Ltd, 442-1, Kato-shi, Hyogo, Japan. Electronic address: h-fujisawa@nippon-zoki.co.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Fujisawa
authors.affiliation: Department of Pharmacological Research, Institute of Bio-Active Science, Nippon Zoki Pharmaceutical Co., Ltd, 442-1, Kato-shi, Hyogo, Japan. Electronic address: t-numazawa@nippon-zoki.co.jp.
authors.forename: Takumi
authors.initials: T
authors.lastname: Numazawa
authors.affiliation: Department of Pharmacological Research, Institute of Bio-Active Science, Nippon Zoki Pharmaceutical Co., Ltd, 442-1, Kato-shi, Hyogo, Japan. Electronic address: m-kawamura@nippon-zoki.co.jp.
authors.forename: Minoru
authors.initials: M
authors.lastname: Kawamura
authors.affiliation: Department of Pharmacological Research, Institute of Bio-Active Science, Nippon Zoki Pharmaceutical Co., Ltd, 442-1, Kato-shi, Hyogo, Japan. Electronic address: m-naiki@nippon-zoki.co.jp.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Naiki
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001831:Body Temperature; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006930:Hyperalgesia / Q000517:prevention & control; D008297:Male; D008636:Mesencephalon / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D011134:Polysaccharides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological; D013379:Substrate Specificity; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D000700:Analgesics; D011134:Polysaccharides; C010491:neurotropin; D002154:Calpain
keywords: Calpain; Central nervous system; Hyperalgesia; Mechanical pain threshold; Munc-18; Neurotropin®; SART stress