Neuropeptide Y- and alpha-adrenergic receptors in pig spleen: localization, binding characteristics, cyclic AMP effects and functional responses in control and denervated animals.
The localization of neuropeptide Y binding sites in the pig spleen, as revealed by [125I]Bolton-Hunter-labelled porcine neuropeptide Y and alpha 1-adrenergic receptor binding sites, as revealed by [125I](2-beta/4-hydroxy-phenyl/-ethylaminomethyl)-tetralone as radioligand, was compared with the distribution of neuropeptide Y and noradrenaline nerves, the latter revealed by tyrosine hydroxylase and dopamine-beta-hydroxylase, using immunohistochemistry. A large degree of codistribution was obtained between [125I]neuropeptide Y and alpha 1-binding sites in the capsule, trabeculae, blood vessels and the red pulp of the spleen. Neuropeptide Y and tyrosine hydroxylase as well as dopamine-beta-hydroxylase-positive nerves were identical in the spleen and had a similar gross distribution pattern as the [125I]neuropeptide Y and alpha 1 binding sites. In functional studies using the isolated blood-perfused spleen from pentobarbital-anaesthetized pigs, neuropeptide Y, noradrenaline and the alpha 1-selective agonist phenylephrine contracted the capsule and induced vasoconstriction in the spleen in vivo. However, the selective alpha 2-adrenoceptor agonists clonidine and azepexole had no effects on blood flow or perfusion pressure, suggesting that postjunctional alpha-receptors were of the alpha 1 type. Neuropeptide Y inhibited the forskolin-evoked, cyclic adenosine monophosphate formation in vitro. The [125I]neuropeptide Y binding, with an equilibrium-dissociation constant of 503 +/- 73 pM and a maximal number of specific binding sites of 23 +/- 3 fmol/mg protein, the neuropeptide Y-induced perfusion-pressure increase in vivo and the inhibition of forskolin-evoked cyclic adenosine monophosphate formation in vitro were dependent on the amidation of the C-terminal portion of the peptide molecule. Furthermore, the effects of neuropeptide Y were not changed by alpha- and beta-adrenoceptor blockade using prazosin and propranolol. Two weeks after postganglionic denervation the neuropeptide Y and the noradrenaline contents of the pig spleen were reduced by 97% and 99%, respectively. These changes were associated with a selective supersensitivity for the noradrenaline-induced perfusion-pressure increase in vivo compared with the effect of neuropeptide Y. However, a similar potentiation of the noradrenaline effect was induced by the monoamine-uptake blocker desipramine in the absence of denervation, and there was no change in the functional response to phenylephrine after denervation.(ABSTRACT TRUNCATED AT 400 WORDS)
Lundberg
J M
JM
Department of Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Hemsén
A
A
Rudehill
A
A
Härfstrand
A
A
Larsson
O
O
Sollevi
A
A
Saria
A
A
Hökfelt
T
T
Fuxe
K
K
Fredholm
B B
BB
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D001783:Blood Flow Velocity / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D003714:Denervation; D007150:Immunohistochemistry; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D017476:Receptors, Neuropeptide Y; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D013154:Spleen / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D013552:Swine
D009478:Neuropeptide Y; D011942:Receptors, Adrenergic, alpha; D017476:Receptors, Neuropeptide Y; D017981:Receptors, Neurotransmitter; D005576:Colforsin; D000242:Cyclic AMP; D009638:Norepinephrine