Changes in mechanism of PACAP-induced relaxation in longitudinal muscle of the distal colon of Wistar rats with age
| Autor: | Yasuko Yamazaki, Tadashi Takewaki, Kaori Fujinami, Akikazu Fujita, Tadayoshi Takeuchi, Fumiaki Hata, Kazunori Mukai, Tamotsu Negoro |
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| Rok vydání: | 2003 |
| Předmět: |
Male
endocrine system medicine.medical_specialty Arginine Physiology Colon Muscle Relaxation Clinical Biochemistry Neuropeptide Apamin Biochemistry Nitric oxide SK channel Cellular and Molecular Neuroscience chemistry.chemical_compound Endocrinology Internal medicine medicine Animals Rats Wistar Protein kinase A Neuropeptides Age Factors Muscle Smooth Rats Pituitary adenylate cyclase-activating peptide chemistry Tetrodotoxin Pituitary Adenylate Cyclase-Activating Polypeptide Female hormones hormone substitutes and hormone antagonists |
| Zdroj: | Regulatory peptides. 118(1-2) |
| ISSN: | 0167-0115 |
| Popis: | Mechanisms of relaxation of longitudinal muscle of the distal colon induced by exogenously added pituitary adenylate cyclase activating peptide (PACAP) were studied in 2- to 30-week-old Wistar rats. Exogenous PACAP induced very significant relaxation of the longitudinal muscle in 2-week-old rats, but this effect decreased significantly with age. The cyclic AMP–cyclic AMP-dependent protein kinase (PKA) pathway and the tyrosine kinase–small conductance Ca 2+ -activated K + channel (SK channel) pathway were found to be involved in the mechanism of PACAP-induced relaxation. In 2-week-old rats, PACAP-induced relaxation was significantly inhibited by tetrodotoxin (TTX). Since relaxation was also significantly inhibited by N G -nitro- l -arginine ( N 5 -nitro-amidino- l -2,5-diamino-pentanoic acid: l -NOARG), the neurogenic effect of PACAP seems to be mediated mainly through nitric oxide neurons. In 8-week-old rats, l -NOARG and TTX had little effect on PACAP-induced relaxation, suggesting that the relaxant effect in 8-week-old rats is a direct action on longitudinal smooth muscle cells. Changes in the mechanisms of PACAP-induced relaxation with age were examined in the distal colon in relation to changes in the neurogenic and the direct effects of PACAP. The neurogenic effect in the exogenous PACAP-induced relaxation of the longitudinal muscle of the Wistar rat distal colon is dominant in tissue isolated from 2-week-old and lost in tissue isolated from 8-week-old rats. |
| Databáze: | OpenAIRE |
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