Pre- and postjunctional actions of neuropeptide Y and related peptides.

Abstract The effects of neuropeptide Y (NPY) and related peptide fragments on blood pressure and vagal action at the heart were compared in the anaesthetized rat. A change in vagal action was taken as a measure of presynaptic activity and a change in blood pressure was taken as a measure of postsynaptic activity. NPY, NPY-(13–36), PYY-(13–36), des-Ser 22 -NPY-(13–36) and a stabilized 13–36 analogue of NPY (ANA NPY) all exerted pressor actions and attenuated vagal action at the heart. The maximum vagal inhibitory or presynaptic action in order of potency was NPY, ANA-NPY, PYY-(13–36) significantly greater than NPY-(13–36), des-Ser 22 -NPY-(13–36). The order of potency for the half time of this effect was NPY, ANA-NPY significantly longer than PYY-(13–36) and NPY-(13–36), which were significantly longer than des-Ser 22 -NPY-(13–36). For the pressor or postsynaptic effects, NPY increased blood pressure significantly more and for a longer duration than all the 13–36 fragments, which were not demonstrably different in this respect. These results are consistent with the proposal that there are two populations of NPY receptors. The C-terminal flanking peptide of NPY (CPON) and desamido-NPY had no effect on either vagal action at the heart or on blood pressure.