Involvement of neuronal processes and nitric oxide in the inhibition by endotoxin of pentagastrin-stimulated sastric acid secretion

Abstract

Administration of E. coli endotoxin (1 mg kg⁻¹, i.v.) abolished the acid response induced by the i.v. infusion of pentagastrin (8 μg kg⁻¹, h^-1) in the continuously perfused stomach of the anaesthetized rat. Local serosal application of tetrodotoxin (36 ng per rat) completely restored acid responses to pentagastrin in endotoxin-treated rats. However, pretreatment with atropine (0.5 mg kg⁻¹, s.c.), capsaicin (20, 30, and 50 mg kg⁻¹, s.c. 2 weeks before the study) or guanethidine (16 mg kg⁻¹, s.c. 3 and 16h before) did not influence the inhibitory effects of endotoxin. Continuous i.v. infusion with N^G-nitro arginine methyl ester (L-NAME, 10 mg kg⁻¹, h⁻¹) restored the secretory responses to pentagastrin in endotoxin treated rats. The effects of L-NAME were reversed by L-arginine (100 mg kg⁻¹, h⁻¹, i.v.), but not by its enantiomer D-arginine (100 mg kg⁻¹, h⁻¹, i.v.). The secretory responses elicited by pentagastrin (10⁻¹⁰–10⁻⁶ M) in the isolated lumen perfused stomach of the rat were not influenced by incubation (100 min) with endotoxin (10 μg ml ⁻¹). These observations with tetrodotoxin indicate that inhibition of acid secretion by endotoxin in vivo involves neuronal activity, while inhibition of NO synthesis had a comparable inhibitory action. Activation of a systemic non-adrenergic non-cholinergic neuronal pathway involving NO could thus mediate the acute acid inhibitory effects of endotoxin.