Involvement of nitric oxide in the mediation of NANC inhibitory neurotransmission of guinea- pig trachea
| Autor: | T. J. Maher, M. J. Krautmann, E. P. Holmes, Changaram S. Venugopalan |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Male
medicine.medical_specialty Guinea Pigs Stimulation Neurotransmission Nitric Oxide Synaptic Transmission Nitric oxide Guinea pig chemistry.chemical_compound Quinoxalines Internal medicine medicine Animals Receptors Cholinergic Enzyme Inhibitors Neurotransmitter Methemoglobin Pharmacology Oxadiazoles Dose-Response Relationship Drug General Neuroscience Neural Inhibition Receptors Adrenergic Methylene Blue Trachea Atropine Endocrinology chemistry Guanylate Cyclase Anesthesia Cholinergic Female Pouch medicine.drug |
| Zdroj: | Journal of Autonomic Pharmacology. 18:281-286 |
| ISSN: | 1365-2680 0144-1795 |
| DOI: | 10.1046/j.1365-2680.1998.18595.x |
| Popis: | 1 The involvement of nitric oxide (NO) in the non-adrenergic non-cholinergic inhibitory (NANC-i) neurotransmission was evaluated in guinea-pigs anaesthetized with chloralose–urethane, using a tracheal pouch preparation. 2 The tracheal pouch, a surgically isolated segment of trachea with intact nerve and blood supply, is an in situ method to demonstrate NANC-i response after complete cholinergic and adrenergic blockade using atropine (5 mg kg−−1) and propranolol (1 mg kg−−1), respectively. Cervical vagi and sympathetic trunks were isolated and cut cranially. The distal ends of the vagi were positioned on bipolar electrodes for subsequent stimulation with 5 V pulses for 2 ms duration at 15 Hz for a total of 90 s. The relaxation response was measured as a pressure drop (cm of H2O) in the pouch. Each experimental group was composed of six animals. 3 NANC-i responses to two consecutive nerve stimulations at 25 min apart were reproducible. 4 Pouch relaxation responses to electrical nerve stimulations were determined before and after incubation of the pouch with Nω-nitro-l-arginine methyl ester (l-NAME; 10−−5 m), a NO synthase (NOS) inhibitor, for 30 min. l-NAME significantly, but not completely, inhibited the NANC-i response of the pouch, suggesting involvement of NO in the NANC-i neurotransmission. 5 The pouch relaxations to vagal stimulations were inhibited significantly after incubation with oxyHb indicating that NO was released. 6 The amount of methaemoglobin (metHb) formed from oxyhaemoglobin (oxyHb) during vagal stimulation was measured by spectrophotometry. Comparison of the values between the control and after nerve stimulation indicated a trend (P = 0.07) toward greater metHb formation in the pouch perfusate after nerve stimulation. 7 NANC-i responses were not significantly inhibited by incubation of the pouch with either of the guanylate cyclase inhibitors, methylene blue or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). However, a trend toward significance (P ≤ 0.07) was observed. 8 This study demonstrated that NO is involved in NANC-i neurotransmission. However, the findings did not conclusively support the contention that NO is the sole neurotransmitter of NANC inhibition. It is possible that NO produced relaxation of guinea-pig trachea through a cGMP-independent mechanism. |
| Databáze: | OpenAIRE |
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