Effect of the N-terminal tetrapeptide of substance P SP (1-4) and tuftsin on the pre- and postsynaptic transmitter outflow in rat adrenal gland slices.

Two structurally related tetrapeptides, the N-terminal tetrapeptide of substance P SP(1-4) and tuftsin, exerted some similarities in modifying immune reactions and normalizing stress-induced disorders in the catecholamine system of adrenals. This paper presents results about the effects of tuftsin and SP(1-4) on the cholinergic-adrenergic interaction in rat adrenal gland slices. Both, tuftsin and SP(1-4) inhibited the nicotine-evoked [3H]noradrenaline outflow (postsynaptic effect), but the effect of SP(1-4) was more pronounced. SP(1-4) also inhibited the electrically stimulated [3H]ACh outflow (presynaptic effect), whereas tuftsin did not affect the ACh outflow. It is suggested that the regulation of the cholinergic-adrenergic interaction in adrenals is mediated by specific receptors, which are different on the pre- and postsynaptic side.