Mv. Donoso et al., Neuropeptide Y contribution to the physiology of human sympathetic co transmission. Studies in saphenous vein biopsies, REV MED CHI, 128(8), 2000, pp. 829-838
Background: It is known that the sympathetic varicosities co-store and co-r
elease norepinephrine (NE) together with adenosine S-triphosphate (ATP) and
neuropeptide Y (NPY). Aim: To describe the chemical characterisation of st
ored and released NPY from the varicosities of sympathetic nerve terminals
surrounding segments of the human saphenous vein, and the vasomotor activit
y of rings electrically depolarized or contracted by the exogenous applicat
ion of the co-transmitters. Material and methods: Saphenous vein tissues we
re obtained from patients undergoing elective cardiac revascularization sur
gery. Results: The chromatographic profile of NPY extracted from biopsies i
s identical to a chemical standard of human NPY. Upon electrical depolarisa
tion of the perivascular sympathetic nerve terminals, we demonstrated the r
elease of NPY to the superfusion media, which did not exceed a 1% of its st
ored content. The release of the peptide is sensitive to guanethidine, and
to extracellular calcium, suggesting that the mechanism of its release is e
xocytotic in nature. The electrically evoked suggesting that the mechanism
of its release is exocytotic in nature. The electrically evoked release of
NPY is dependent on the frequency and duration of the electrical pulses. Ph
enoxybenzamine reduces the electrically evoked release of NPY. Exogenous ap
plication of NE and ATP contract saphenous vein rings; the simultaneous app
lication of NE plus ATP causes a synergic response, effect which is further
potentiated by the joint co-application of 10 nM NPY. Conclusions: Present
results highlight the role of NPY as a sympathetic co-transmitter in the r
egulation of human vascular tone.