Pandya K H
Arch Int Pharmacodyn Ther. 1977 Nov;230(1):53-64.
Age-related changes in responses of tracheal muscle strip to norepinephrine (NE), epinephrine (E), phenylephrine (PE), dopamine (DA) and isoproterenol (IP) were examined in dogs 1-55 days of age. NE, E, PE and DA contract tracheal muscle in dogs 1-12 days of age. NE- and E-induced contractions are potentiated by propranolol. Contractile responses are little affected by atropine, but are completely blocked by phenoxybenzamine or phentolamine. NE-, E-, PE-, and DA-induced contractions gradually decrease with increasing age. Acetylcholine (ACh) contracts and IP slightly relaxes the tracheal muscle at all ages studied. On ACh-contracted tracheal muscle, PE and DA at all ages, and E and NE in 1-18 day old animals, induce a superimposed contraction (SIC) while IP causes a superimposed relaxation (SIR) at all ages. After approximately day 18, E and NE induce SIR while PE and DA still elicit a SIC on ACh-contracted tracheal muscle. These results suggest that E, NE, PE and DA contract the tracheal muscle through alpha adrenergic stimulation; however, beta adrenoceptors seem to be present and functioning to relax the tracheal muscle. As age advances the alpha receptor responses progressively decline; however, alpha receptors still respond to adrenergic agonists at relatively lower level of sensitivity in older animals.
在1至55日龄的犬中研究了气管肌条对去甲肾上腺素（NE）、肾上腺素（E）、苯肾上腺素（PE）、多巴胺（DA）和异丙肾上腺素（IP）反应的年龄相关性变化。在1至12日龄的犬中，NE、E、PE和DA使气管肌收缩。普萘洛尔可增强NE和E诱导的收缩。阿托品对收缩反应影响较小，但苯氧苄胺或酚妥拉明可完全阻断该反应。NE、E、PE和DA诱导的收缩随年龄增长逐渐减弱。在所有研究的年龄阶段，乙酰胆碱（ACh）使气管肌收缩，IP使气管肌轻度舒张。在ACh收缩的气管肌上，所有年龄段的PE和DA，以及1至18日龄动物的E和NE，均可诱导叠加收缩（SIC），而IP在所有年龄段均可诱导叠加舒张（SIR）。大约在18日龄后，E和NE诱导SIR，而PE和DA在ACh收缩的气管肌上仍可引发SIC。这些结果表明，E、NE、PE和DA通过α肾上腺素能刺激使气管肌收缩；然而，β肾上腺素能受体似乎也存在并发挥作用使气管肌舒张。随着年龄增长，α受体反应逐渐下降；然而，在老年动物中，α受体仍以相对较低的敏感性对肾上腺素能激动剂作出反应。
