Endotoxin stimulates fecal pellet output in rats through a neural mechanism.
The effects of endotoxin on fecal pellet output and the neural mechanisms involved in this response were investigated in conscious rats. E. coli endotoxin (40 micro g/kg i.p.) significantly increased fecal excretion for 3 h after the injection. Water content in feces was not modified by endotoxin. Ablation of primary afferent neurons by systemic administration of high doses of capsaicin (20+30+50 mg/kg s.c.) to adult rats prevented the stimulatory effect of endotoxin and so did abdominal vagotomy. Adrenoceptor blockade with phentolamine (5 mg/kg i.p.) + propranolol (3 mg/kg i.p.) did not modify pellet output in endotoxin-treated rats while muscarinic receptor blockade with atropine (1 mg/kg i.p.) abolished the stimulatory effect of endotoxin. Finally, the increase in pellet output induced by endotoxin was prevented in animals receiving the substance P receptor antagonist D-Pro2, D-Trp7,9-substance P (2 mg/kg i.p.) or the NO-synthase inhibitor L-NAME (10 mg/kg i.p.). None of the above treatments modified pellet output in saline-treated rats. These observations indicate that endotoxin increases fecal pellet output through a nervous reflex in which capsaicin-sensitive afferent neurons and the release of excitatory (acetylcholine and substance P) and inhibitory (NO) neurotransmitters in the colonic wall are involved.
Calatayud
Sara
S
Unidad Mixta de Investigación, Facultad de Medicina/Hospital Clínico Universitario, Avda. Blasco Ibáñez 17, 46010 Valencia, Spain.
Barrachina
Maria Dolores
MD
Quintana
Elsa
E
Ibiza
Sales
S
Esplugues
Juan V
JV
D000818:Animals; D003672:Defecation / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000494:pharmacology*; D005243:Feces; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D004731:Endotoxins