title: Effect of L-NAME microinjected into the nucleus tractus solitarius on jejunal glucose and electrolyte absorption in anesthetized rats.
abstract: The aim of the present study was to investigate the effects of N(G)-nitro-L-arginine-methyl-ester (L-NAME) microinjected into the rostral nucleus tractus solitarius (NTS) on jejunal glucose, sodium and potassium absorption. Male Wistar rats (210-250 g, n=6-12) were anesthetized and submitted to midline laparotomy to expose and isolate 20 cm of jejunal loop and perform a subdiaphragmatic truncal vagotomy or sympathectomy. Either 0.9% NaCl or L-NAME (10 nmol 100 nl⁻¹) was microinjected into the rostral NTS using a stereotaxic instrument. Tyrode solution (pH 8) containing twice the usual concentrations of glucose, sodium and potassium was infused (0.5 ml min⁻¹) into the jejunal loop and samples were taken at 10-min intervals during the 40-min experiment. Results were expressed by the difference between influx and efflux. L-NAME into the NTS increased glucose absorption and decreased potassium absorption when compared to the saline group (38.8 ± 3.8 vs. 50.3 ± 3.3 mg/dl and 0.6±0.01 vs. 0.4 ± 0.03 mM, respectively; p<0.05). Sympathectomy inhibited the glucose absorption caused by L-NAME alone (50.3 ± 3.3 vs. 30.7 ± 4.6 mg/dl; p<0.05), whereas vagotomy inhibited the L-NAME effect on potassium absorption (0.40 ± 0.02 vs. 0.70 ± 0.05; p<0.05). Moreover, increased sodium absorption was observed only in the group that received 30 nmol of L-NAME into NTS (33.0 ± 4.2 vs. 48.4 ± 3.9). In conclusion, the results suggest the participation of endogenous nitric oxide (NO) in the NTS in modulating intestinal glucose and potassium absorption mediated by the autonomic nervous system.
authors.affiliation: Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Marcelo Coelho
authors.initials: MC
authors.lastname: Nogueira
authors.forename: Andréa Siqueira
authors.initials: AS
authors.lastname: Haibara
authors.forename: Elizabeth Lage
authors.initials: EL
authors.lastname: Borges
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology*; D004573:Electrolytes / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008845:Microinjections; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism*; D013562:Sympathectomy; D014628:Vagotomy
chemical_list: D004573:Electrolytes; D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D005947:Glucose; D019331:NG-Nitroarginine Methyl Ester