Somatosensory Physiology

Abstract

Chronic stress is known to affect the clinical symptoms of rheumatoid arthritis in humans, though the exact biochemical evidence is lacking. Under experimental conditions, partial food deprivation represents, aside from metabolic changes , emotional stress accompanied by chronic activation of the hypothalamo-pituitary-adrenocortical axis (Han et al. 1995).The model of chronic activation of hypothalamo-pituitaryadrenocortical axis by food restriction was used to determine whether stress-activated mechanisms might alleviate the development of adjuvant arthritis in rats. Four groups of rats (n = 3S) were used : intact control rats fed ad libitum (C), food -restricted rats fed 60% of C food intake (FR), arthritic rats fed ad libitum (AA) , and arthritic rats fed 60 % of AA food intake (AA-FR). Adjuvant arthritis was induced by the s.c. injection of dead Mycobacterium butyricum into the tails of male rats of the Long-Evans strain .Serum corticosterone (Cort) was elevated in the FR group (15'49 ± 2'1 flg 100 ml-1 vs. C, 5'02 ± O'OS flg 100 ml-1 , ANOVA, P< 0'01, mean ± S.E.M.). In the AA-FR group, no significant elevation of Cort was found. Enhanced hindpaw swelling (volumetric method) found in the AA group (2'37 ± 0'15 ml vs. C, 1'1 ± 0'05 ml, P< 0'01) was attenuated by stress. Serum albumin , as a negative acute phase reactant, was reduced in AA rats (23'9 ± 0'5 g 1-1 vs.C, 37'2 ± 0'05 g 1-1, P < 0'01) and chronic stress restored its levels (2S'1 ± 0'96 g 1-\ P< 0'01). The elevated level of serum N0 2 -/N0 3 -in AA rats (47' S ±5'7 flmoll-l vs. C, 11'3 ± 2'6 flmoll-l) was normalized in AA-FR animals (24'3 ± 3'9 flmoll-l) as well as the total antioxidative capacity in the spleen (O' S ± 0'04 mmoll-' vs. 0'66 ± 0'06 mmoll-1 ) . Higher pain-induced analgesia in AA (S'72 ± 0'34 s vs. C, 3'56 ± 0'21 s) rats as measured by tailflick was restored in the AA-FR group (6'OS ± 0'36 s).These results show an overall beneficial effect of chronic stress (food deprivation) for the development of adjuvant arthritis in rats fed ad libitum.Supported by Grant Agency of the Czech Republic -GACR 305/95/05712.