Neuropeptide Y potentiates excitation of supraoptic neurosecretory cells by noradrenaline. 
The effects of neuropeptide Y (NPY) and noradrenaline (NA) on the activity of rat supraoptic nucleus (SON) neurosecretory cells were examined using perfused hypothalamic slices.  Bath application of either NPY (10(-9)-10(-6) M) or NA (10(-6)-10(-3) M) excited SON cells, although only NA elicited consistent, dose-dependent effects.  Application of NPY at a dose having virtually no direct effects (10(-8) M) produced a 5-fold increase in SON cell responsiveness to NA at the sub-maximal response dose of 10(-5) M, but did not alter the minimum concentration of NA required to excite SON cells or increase the maximal response elicited by higher NA concentrations.  The effects of NA, alone or in combination with NPY, were abolished by alpha-adrenoreceptor blockade.  These data suggest that NPY has only weak direct effects on neurosecretory cells, but may have important neuromodulatory actions, significantly enhancing the excitatory effects of NA.