Figure 4

Effect of various Y ₁ affine analogs on forskolin-stimulated intracellular cAMP accumulation in SK-N-MC cells. Cells were incubated for 30 min with 10 μM forskolin either alone, or with 10 μM forskolin in the presence of 20 μM or 100 nM of the reference compound [Leu³¹, Pro³⁴]-PYY (LP-PYY), or with 10 μM forskolin in the presence of the various Y₁ affine analogs either alone at a concentration of 20 μM or at a concentration of 20 μM in the presence of 100 nM LP-PYY. Intracellular cAMP accumulation was then determined as described in Methods. Results are shown as percentage of the 10 μM forskolin effect on intracellular cAMP accumulation. While the 10 μM forskolin effect is efficiently inhibited by the agonist LP-PYY at 20 μM and 100 nM, all tested analogs behave as antagonist since given alone they are not able to inhibit the forskolin effect while they completely and efficiently antagonize the 100 nM effect of LP-PYY.