Neuropeptide Y overflow and metabolism in skeletal muscle arterioles

Non‐technical summary Neuropeptide Y (NPY) is involved in a number of vascular physiological processes that affect sympathetic neurotransmission and angiogenesis. While NPY is of physiological significance, very little is known regarding local overflow characteristics at specific levels of the vasculature. Through the use of a new technique, we were able to quantify NPY overflow from isolated skeletal muscle arterioles of female rats. We observed age‐related differences in NPY overflow and its degradation via dipeptidyl peptidase IV. These results will provide insights into the release and breakdown of NPY at local levels of the vasculature. The purpose of this study was to characterize neuropeptide Y (NPY) overflow and metabolism from isolated skeletal muscle arterioles of female rats. Gastrocnemius first‐order arterioles were removed from young (2 months), young adult (6 months) and middle‐aged (12 months) F344 female rats. Arterioles were isolated, cannulated and pressurized in a microvessel bath with field stimulation electrodes. NPY overflow from isolated arterioles was assessed at 0 s and 30 s post‐field stimulation. Dipeptidyl peptidase IV (DPPIV) activity was quantified via fluorometric assay of whole vessel homogenate. In young adult and middle‐aged rats, NPY overflow increased 0 s and 30 s following field stimulation. In young adult rats, DPPIV inhibition resulted in an increase in NPY overflow at 30 s, while middle‐aged rats had no increase in NPY overflow with DPPIV inhibition (P < 0.05). DPPIV activity was influenced by factors such as age, vessel type, and endothelium (P < 0.05). The present data suggest that DPPIV plays a significant role in modulating the actions of NPY in arterioles of young adult females; however, this role appears to diminish with age.