Neuropeptide Y and peptide YY inhibit adenylate cyclase activity in the rat striatum

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Abstract
The equilibrium binding of [3H]propionyl neuropeptide Y ([3H]pNPY) to receptors in a crude synaptic membrane preparation from the rat striatum was influenced by GTP, which caused an apparent loss of high-affinity binding sites for [3H]pNPY. In the presence of GTP (10-5 M), NPY and peptide YY (PYY) inhibited basal and forskolin-stimulated adenylate cyclase activity in a concentration-dependent manner in a cell-free preparation from rat striatum. The IC50 values for NPY and PYY were 1 times 10 8 M and 1.4 × 10-8 M respectively. The inhibitory action of NPY (10-6 M) or of PYY (10-6 M) was additive to that of acetylcholine (10-4 M). The two peptides together also showed additivity (P < 0.05) in inhibiting adenylate cyclase.