[Neuropeptide Y contribution and the physiology of human sympathetic co-transmission. Studies in saphenous vein biopsies].
BACKGROUND
It is known that the sympathetic varicosities co-store and co-release norepinephrine (NE) together with adenosine S-triphosphate (ATP) and neuropeptide Y (NPY).


OBJECTIVE
To describe the chemical characterization of stored and released NPY from the varicosities of sympathetic nerve terminals surrounding segments of the human saphenous vein, and the vasomotor activity of rings electrically depolarized or contracted by the exogenous application of the co-transmitters.


METHODS
Saphenous vein tissues were obtained from patients undergoing elective cardiac revascularization surgery.


RESULTS
The chromatographic profile of NPY extracted from biopsies is identical to a chemical standard of human NPY. Upon electrical depolarisation of the perivascular sympathetic nerve terminals, we demonstrated the release of NPY to the superfusion media, which did not exceed a 1% of its stored content. The release of the peptide is sensitive to guanethidine, and to extracellular calcium, 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. Phenoxybenzamine reduces the electrically evoked release of NPY. Exogenous application of NE and ATP contract saphenous vein rings; the simultaneous application 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 regulation of human vascular tone.
Donoso
M V
MV
Departamento de Fisiología, Unidad de Regulación Neurohumoral, Facultad de Ciencias Biológicas, Universidad Católica de Chile, Santiago, Chile.
Miranda
R
R
Irarrázaval
M J
MJ
Morán
S
S
Zalaquett
R
R
Huidobro-Toro
J P
JP
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D004558:Electric Stimulation; D006801:Humans; D009478:Neuropeptide Y / Q000032:analysis / Q000494:pharmacology / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D017933:Peripheral Nervous System / Q000187:drug effects; D012501:Saphenous Vein / Q000737:chemistry / Q000187:drug effects / Q000294:innervation*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D014655:Vascular Resistance
D009478:Neuropeptide Y; D018377:Neurotransmitter Agents; D000255:Adenosine Triphosphate; D009638:Norepinephrine