Effects of Prostaglandins on Excitatory Transmission in Isolated Canine Tracheal Muscle

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Abstract
Contractile response of the isolated canine tracheal muscle to transmural nerve stimulation was considerably depressed by 10-6 g/ml of prostaglandin[PG]A1 PGA2, PGB2, PGE1, PGE2 and PGF2.alpha., while the response to exogenously administered ACh [acetylcholine] was only slightly affected by the pretreatment with prostaglandins (PGs). The order of the potency of the depressive effect was as follows; PGE1 > PGE2 > PGA1 > .**GRAPHIC**. Therefore, if a negative feedback control mechanism through prostaglandins exists in the excitatory transmission in canine tracheal muscle, the PGE series may predominantly operate the mechanism. Indomethacin in a dose of 10-6 g/ml produced a potentiation of the contractile responses to transmural nerve stimulation and to exogenously administered ACh.