Growth hormone releasing hormone reverses endotoxin-induced localized inflammatory hyperalgesia without reducing the upregulated cytokines, nerve growth factor and gelatinase activity

Rabih S. Talhouk, Nayef E. Saadé, Ghassan Mouneimne, Cynthia A. Masaad, Bared Safieh-Garabedian

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

During inflammatory processes, the hypothalamic-pituitary axis is activated which can subsequently result in analgesia. For example, hypothalamic corticotrophin-releasing hormone (CRH) that is released during such activation has been attributed with analgesic actions. It is believed that the somatotrophic axis is also activated during inflammation. The aim of this study was to determine the analgesic actions of growth hormone-releasing hormone (GHRH), in a rat model of localized inflammatory hyperalgesia, induced by intraplantar (i.pl.) endotoxin (ET) injections. Pretreatment with intraperitoneal (i.p.) injections of GHRH (2, 5, 10 μg kg-1) 30 min before i.pl. ET injection (1.25 μg in 50 μl saline) prevented, in a dose-dependent manner, both mechanical hyperalgesia determined by the paw pressure (PP) test and thermal hyperalgesia determined by the hot plate (HP) and paw immersion (PI) tests. Pretreatment with GHRH had no significant effect on the elevated levels of the inflammatory mediators, interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6 and nerve growth factor (NGF) due to i.pl. ET injection. No significant effect was obtained by pretreatment with GHRH, on the increased expression of gelatinase B due to ET injection. In conclusion, GHRH reverses inflammatory hyperalgesia in the rat without affecting the upregulated inflammatory mediators and these actions may be clinically important.

Original languageEnglish (US)
Pages (from-to)625-631
Number of pages7
JournalProgress in Neuro-Psychopharmacology and Biological Psychiatry
Volume28
Issue number4
DOIs
StatePublished - Jul 1 2004
Externally publishedYes

Keywords

  • CNS
  • CRH
  • Cytokines
  • ELISA
  • ET
  • Enzyme-Linked Immunosorbent Assay
  • GH
  • GHRH
  • Gelatinase B
  • HP
  • HPA
  • Hyperalgesia
  • Inflammation
  • NGF
  • central nervous system
  • corticotrophin-releasing hormone
  • endotoxin
  • growth hormone
  • growth hormone-releasing hormone
  • hot plate

ASJC Scopus subject areas

  • Pharmacology
  • Biological Psychiatry

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