Involvement of L-arginine-nitric oxide system in the response of isolated trachea to reactive oxygen species.

The aim of this study was to investigate the effect of reactive oxygen species (ROS), generated by electrolysis of Krebs-Henseleit solution (GE-KHS), on isolated guinea pig trachea and to assess the possible involvement of nitric oxide (NO) in the observed effects. The isolated trachea was superfused in GE-KHS, generating H2O2 and hypochlorous acid (HOCl), both of which slowly increased in the organ bath and reached final stable concentrations of 42 and 63 microM, respectively, at the rate of 20 ml/min(-1), and 261 and 245 microM, respectively, at the rate of 5 ml/min(-1). ROS GE-KHS-induced relaxation of tracheal rings was preceded by a small transient contraction in 40% and 65% of experiments when tracheal rings were superfused at the rate of 20 ml/min(-1) and 5 ml/min(-1), respectively.

Evidence for a neurotransmitter role of glutamate in guinea pig myenteric plexus neurons.

Longitudinal muscle-myenteric plexus strips of the guinea pig ileum were used to investigate a possible transmitter role of glutamate (Glu) in the enteric nervous system. Glu was released from this nerve muscle preparation by high K(+)-depolarization in a Ca2(+)-dependent manner, by electrical field stimulation and by the ganglionic stimulant dimethylphenylpiperazinium which indicates its neural origin. Contractions of the longitudinal muscle evoked by electrical stimulation of the myenteric nerves or by Glu, were significantly reduced by the N-methyl-D-aspartate (NMDA)-receptor antagonist FR115427 (9 and 18 microM), whereas contractions induced by histamine were unaffected.