Alternation by histamine receptor agonists of the release of adrenergic transmitter in the isolated perfused rabbit kidney.

The effects of histamine and synthetic H1 and H2-receptor agonists on the release of neurotransmitter were studied in the isolated perfused rabbit kidney. The increase in perfusion pressure and the contraction of the venous outflow-superfused rabbit aortic strip were taken as the parameters for the evaluation of the elaboration of neuromediator from the kidney du to periarterial stimulation. Histamine and te specific histamine H1-receptor agonist, 2-(2-thiazolyl) ethylamine, caused a significant increase but the specific H2-receptor agonists, dimaprit and impromidine, produced a significant decrease in the response due to periarterial stimulation without altering that of exogenously applied noradrenaline. Prior addition of mepyramine to the medium prevented effect of 2-(2-thiazolyl) ethylamine but caused a high significant decrease in the response produced by histamine when compared with the control values. Prior addition of metiamide to the medium, however, prevented the inhibitory effect of dimaprit and impromidine but potentiated the effect of histamine. From these results it was concluded that histamine has a presynaptic H1-mediated facilitatory and H2-mediated inhibitory effects on the release of neurotransmitter from adrenergic neurons in the isolated perfused rabbit kidney.