Effect of lipopolysaccharide treatment on neurogenic contraction and noradrenaline release in rat arteries

In the present study, contractile responses and [H-3]-noradrenaline overflo w evoked by electrical field stimulation were assessed, respectively, in th e small mesenteric artery and in tail artery removed from rats pre-treated with either saline or lipopolysaccharide (LPS). In small mesenteric arterie s. LPS treatment did not significantly modify the contractile responses eli cited by electrical stimulation, in the absence or in the presence of L-arg inine. However, in arteries removed from rats treated with LPS, L-arginine addition produced relaxation of vessels pre-contracted with noradrenaline, The amplification of neurogenic contraction by the nitric oxide (NO) syntha se inhibitor NW-nitro-L-arginine methyl ester (L-NAME) was similar in arter ies removed from saline and LPS-infused rats. In mesenteric arteries, LPS t reatment suppressed the potentiation of the neurogenic responses by the alp ha (2)-adrenoceptor antagonist, yohimbine and by the inhibitor of neuronal uptake of noradrenaline, cocaine. In rat tail artery exposed to L-arginine, LPS treatment produced an increase in [H-3]-noradrenaiinc overflow evoked by electrical stimulation. Altogether, these data suggest that an enhanced noradrenaline release from sympathetic nerves, probably resulting from inhi bition of the modulatory effect of birth prejunctional alpha (2)-adrenocept ors and neuronal uptake mechanism, may play a role in the preservation of n eurogenic response after LPS treatment despite evidence of the induction of NO synthase. (C) 2000 Editions scientifiques et medicales Elsevier SAS.