EFFECTS OF PROSTAGLANDINS ON EXCITATORY TRANSMISSION IN ISOLATED CANINE TRACHEAL MUSCLE

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Contractile response of the isolated canine tracheal muscle to transmural nerve stimulation was considerably depressed by 10^-6 g/ml of prostaglandin Al (PGA₁), A₂ (PGA₂), B₂ (PGB₂), E₁ (PGE₁), E₂ (PGE₂) and F_2α (PGF_2α), while the response to exogenously administered ACh 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>PGA₂≈PGB₂≈PGF2_2α. 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.