The effect of some phenylethanolamine N-methyltransferase inhibitors on the adrenaline content in the domestic fowl diencephalon

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Abstract
Concentration of adrenaline [epinephrine] in the domestic fowl [Gallus domesticus] diencephalon was determined by mass spectrometric or fluorimetric method. Values obtained were 701 and 803 ng/g, respectively. The administration of phenylethanolamine N-methyltransferase (PNMT) (EC 2.1.1.28) inhibitors (SK&F 7698 [3-methyl1,2,3,4-tetrahydro[1]benzothieno[3,2C]pyridine hydrochloride] or SK&F 64139 [7,8-dichloro-1,2,3,4-tetrahydroisoquinoline]) to the domestic fowl marked reduced the diencephalic noradrenaline [norepinephrine] methylation (from 25% in controls to 7-8% in the PNMT-inhibitor-treated animals); the large decrease in adrenaline concentration (to 14-18% of controls) was accompanied by moderate decrease in noradrenaline concentration (to 63-84% of controls). Reserpine markedly reduced adrenaline and noradrenaline (to 12 and 17% of controls, respectively) but did not affect percentage of methylation. In the domestic fowl diencephalon, adrenaline is probably formed by N-methylation of noradrenaline and functions there as a transmitter in some specific adrenergic neuronal pathways.