A pharmacological study on the role of nitric oxide in the pathogenesis of experimental allergic encephalomyelitis.
OBJECTIVE
The study examines the effects of nitric oxide synthase (NOS) inhibitors on the development of neurological EAE and the levels of nitrite in the central nervous system (CNS) during established disease.


METHODS
EAE was induced in male Lewis rats (200-250 g).


METHODS
Rats received NG-nitro-L-arginine methyl ester (L-NAME) (30 mg/kg body weight) day 7 to 12 post-inoculation (P.I.), 7-nitroindazole (10 mg/kg) day 7 to 11 P.I. or aminoguanidine (200 or 400 mg/kg) day 1 to 12 P.I.


METHODS
Neurological symptoms were assessed and CNS cytosol nitrite and protein levels measured. Results were analysed using the Mann Whitney U-test and the Fischer exact probability test.


RESULTS
Symptoms of EAE were associated with a significant elevation in CNS nitrite (p < 0.001). Treatment with NOS inhibitors caused a marked reduction in nitrite levels (p < 0.01). However, in some experiments, vehicle administration also reduced CNS nitrite content (p < 0.05). Although neurological disease was suppressed in EAE-sensitised rats receiving L-NAME (2 +/- 0.3 vs 3 +/- 0.3 mean peak severity +/- SEM) and 7-nitroindazole (1 +/- 0.3 vs 3 +/- 0.3, p < 0.01) comparable inhibition was achieved by respective vehicle treatment (p < 0.01). In contrast, neither aminoguanidine nor corresponding vehicle altered disease development.


CONCLUSIONS
Drug-induced reductions in CNS nitrite levels during EAE are not always associated with a suppression of neurological symptoms, which suggests NO is not of primary importance in disease pathogenesis. In addition, the study emphasises the strict requirement for appropriate controls when assessing the efficacy of drugs on the course of EAE.
Pharmacology Group, School of Pharmacy & Pharmacology, University of Bath, UK.
G S
GS
Scott
K I
KI
Williams
C
C
Bolton
D000818:Animals; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000209:etiology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009573:Nitrites / Q000032:analysis; D051381:Rats; D011917:Rats, Inbred Lew; D015431:Weight Loss / Q000187:drug effects
D009573:Nitrites; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester