EVALUATION OF AN ELECTROCHEMICAL MICROPROBE FOR DIRECT NO MEASUREMENTIN THE RAT GASTRIC FUNDUS

Nitric oxide (NO) is an inhibitory nonadrenergic, noncholinergic (NANC ) neurotransmitter in the rat gastric fundus and is released upon elec trical or pharmacological stimulation of the inhibitory NANC neurons. In this study, it was attempted to measure the release of NO from the rat gastric fundus upon electrical stimulation or administration of ni cotine directly via an electrochemical probe (ISO-NO). The system was evaluated by adding exogenous NO. Addition of exogenous NO induced con centration-dependent relaxations of the rat gastric fundus and an incr ease in the ISO-NO probe baseline current. The concentration of NO det ected by the ISO-NO probe was lower than the concentration of NO admin istered. When no tissue was present, higher concentrations of NO were detected than in the presence of a tissue. In the absence of 95% 0(2)/ 5% CO2 the concentration of NO detected was highest. Electrical stimul ation induced relaxations of the rat gastric fundus which were reduced by NG-nitro-L-arginine methylester (L-NAME). An increase in the ISO-N O probe baseline current was also observed, but this was due to nonspe cific effects as the response also occurred without a tissue present a nd was not sensitive to L-NAME. Nicotine induced relaxations, which we re reduced by L-NAME, but the ISO-NO probe baseline current remained u naltered, even in the presence of L-arginine plus superoxide dismutase . It can be concluded that it is not possible to detect directly the N O release from the rat gastric fundus upon electrical or pharmacologic al stimulation of the NANC neurons with the ISO-NO probe. (C) 1997 Els evier Science Inc.