AGE-RELATED ALTERATIONS IN THE RESPONSE OF RABBIT TRACHEAL SMOOTH-MUSCLE TO AGENTS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 214  (3) , 675-681
Abstract
In tracheal muscle strips isolated from rabbits of different ages (3-360 days), median effective concentrations of acetylcholine and K+ increased with age. Nicotine (10-4 M)-induced contractions decreased with increasing age. Concentrations of acetylcholine sufficient to elicit the same contraction as that induced by nicotine decreased with age. The contractile response to histamine was reduced with age. Tracheas from mature rabbits, contracted with acetylcholine, relaxed in response to histamine in a dose-dependent manner. The histamine-induced contractions were suppressed by chloropheniramine, while the relaxations were attenuated by cimetidine. The relaxing response to isoproterenol of tracheal strips contracted with acetylcholine was related inversely to age, but the response to prostaglandin[PG]E1 was increased at day 360. The amount of acetylcholine released from excitatory processes related to H1-receptor stimulation in the tracheal smooth muscle decrease with age, but inhibitory processes related to H2-receptor stimulation are enhanced. The .beta. adrenoceptor mechanism apparently deteriorates with age.