Neuropeptide Y enhances the inhibitory effects of clonidine onH-noradrenaline release in synaptosomes isolated from the medulla oblongata of the male rat.

In studies on superfused synaptosomes from the rat medulla oblongata, the inhibitory effects of the α2-adrenergic agonist clonidine (0.1 μM) on potassium (15 mM K) inducedH-noradrenaline (NA) release was potentiated by 20%, when neuropeptide Y was added to the system. The effect of NPY was detectable at low concentrations (1 nM) and was not dose-dependent. Neuropeptide Y alone produced no significant effects onH-NA release. The results may indicate the existence of a presynaptic NPY receptor on the noradrenaline and/or adrenaline nerve terminals, which may enhance the presynaptic α2-adrenoreceptor function to inhibitH-NA release. [ABSTRACT FROM AUTHOR]