Session 24 :Neuro-pharmacologie, inflammation

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Session 24 :Neuro-pharmacologie, inflammation

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ROLE OF PERIPHERAL INFLAMMATION IN HYPERALGESIA INDUCED BY MAGNESIUM DEPLETED DIET IN RATS

S. Begon, A. Eschalier, A. Alloui and C. Dubray

Groupe NPPUA, Laboratoire de Pharmacologie Médicale, Faculté de Médecine, BP38 63001 Clermont-Ferrand, France.

Previous studies showed that magnesium deficient (MD) rats present a generalized inflammation. On the other hand, we observed that, simultaneously, these animals develop a significant lowering of nociceptive thresholds (Dubray and al., 1997). The aim of this experiment was to clarify the relationship between that hyperalgesia and the peripheral inflammation by testing the influence of several drugs on these two effects.

Methods: 3 weeks-old male Wistar rats, were used in these experiments. After weaning, they were fed with a Mg depleted diet (35 mg/kg) over a period of 10 days. Throughout this period, the vocalization pain thresholds was obtained by applying an increasing pressure on the hind paw. Clinical inflammation scores were assessed in parallel by using a specifically developed scale. These two parameters were determined in the control group (saline (S)) and in animals treated with either piroxicam (Pl) (4.5 mg/kg, o.a.d., s.c.), astemizole (AS) (20 mg/kg, o.a.d., p.o.), astemizole + cimetidine (Cl) (25 mg/kg, b.i.d., i.p.), dexamethasone (DX) (1mg/kg, .d., i.p.) or estradiol (ES) benzoate (0.8 mg/kg, o.a.d., s.c.) (n=10/group).

Results: 1) Pain thresholds. In comparison with the control groups, none of the above mentioned treatments avoided the occurrence of hyperalgesia in MD rats. 2) Inflammation. In comparison with the S treated rats, DX and ES quite suppressed the inflammation (maximal changes at day 6: DX=2.48

± 0.68 vs.S=9.87± 1.42 (p