Glutamate mediated responses in isolated trachea preparations from control and ovalbumin sensitized guinea-pigs.
We investigated whether the glutamergic system plays a role in isolated trachea from control and ovalbumin-sensitized guinea-pigs. Electrical field stimulation induced contractile responses in control group, but electrical field stimulation produced relaxation responses in ovalbumin-challenged guinea-pigs. The responses induced by electrical field stimulation in both groups were completely abolished by tetrodotoxin, but unaffected by hexamethonium. DL-2-amino-5-phosphono-valeric acid (D-AP5) caused a concentration-dependent statistically significant inhibition in the contractile responses to electrical field stimulation50 (EFS50) in control guinea-pigs. But in the ovalbumin-challenged groups, D-AP5 did not cause any significant effect on the relaxation response to frequency of field stimulation (EFS50). N(G)-monmethyl-L-argine caused a significant inhibition in the relaxation effect of EFS50. L- and D-glutamate and N-methyl-D-aspartic acid (NMDA) alone had no effect on the resting tension on the trachea in both groups. Carbachol produced concentration-dependent contractile responses in ovalbumin-challenged groups. These results suggested that responses to electrical field stimulation in control groups might be due to NMDA receptor-mediated release of any substance on prejunctional neurones and, alternatively, NMDA might exert a modulatory effect on any substance at prejunctional level. Also, responses to electrical field stimulation in ovalbumin-challenged guinea-pigs might not be mediated by NMDA but rather by increasing the production of nitric oxide by inducible nitric oxide synthase.
Coşkun
Usta
U
Department of Pharmacology, Akdeniz University Faculty of Medicine, 07070 Arapsuyu, Antalya, Turkey. Fcusta@med.akdeniz.edu.tr
Gülay
Sadan
S
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D010047:Ovalbumin / Q000276:immunology*; D017470:Receptors, Glutamate / Q000502:physiology*; D014132:Trachea / Q000187:drug effects / Q000276:immunology / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D002217:Carbachol; D010047:Ovalbumin