Da. Mahns et al., INHIBITION OF SYMPATHETIC CHOLINERGIC VASODILATATION BY A SELECTIVE NPY Y-2 RECEPTOR AGONIST IN THE GRACILIS MUSCLE OF ANESTHETIZED DOGS, Journal of the autonomic nervous system, 68(1-2), 1998, pp. 14-20
Neuropeptide Y (NPY) is known to be co-stored and co-released from sym
pathetic nerve terminals, In the cardiovascular system NPY acts on two
main receptor subtypes. At the postjunctional or Y-1 receptor NPY cau
ses constriction directly in addition to potentiating other vasoconstr
ictor agents. NPY acting at the prejuctional, or Y-2, receptor, inhibi
ts the release of neurotransmitter from autonomic nerve terminals. Tn
these experiments we used the selective Y-2 receptor agonist N-acetyl[
Leu(28), Leu(31)]NPY24-36 to examine the role of NPY in the modulation
of sympathetic vascular control in skeletal muscle in anaesthetised d
oss. No systemic presser or local constrictor activity was observed in
response to N-acetyl[Leu(28), Leu(31)]NPY24-36 administration, theref
ore allowing us to examine the neuroinhibitory actions of NPY in the a
bsence of direct vascular effects on blood flow, Stimulation of the sy
mpathetic nerves to the gracilis muscle engages both sympathetic choli
nergic and sympathetic adrenergic fibres and produces an initial vasod
ilatation followed by a slower vasoconstriction. Nerve evoked vasodila
tation was inhibited by over 50% in the presence of the selective NPY
Y-2 agonist N-acetyl[Leu(28), Leu(31)]NPY24-36. This dilatation uas ab
olished by atropine, confirming its cholinergic nature. N-Acetyl[Leu(2
8), Leu(31)]NPY24-36 was found to have no effect on nerve evoked vasoc
onstriction. The results demonstrate a NPY Y-2-receptor mediated inhib
ition of nerve evoked sympathetic cholinergic vasodilatation but not o
f sympathetic vasoconstriction. (C) 1998 Elsevier Science B.V.