Table 3.

Dynamic cAMP stimulation upon ligand incubation, washout, and α-MSH re-challenge, showing persistent signaling by certain MC4R ligands (adapted from Molden et al. [34]).

MC4R Ligands and Incubation Concentration	Dynamic cAMP Response				Comment
	Time = 0 min	Time = 10–20 min	Time = 20–50 min	Time = 55–60 min
	Initial (time 0–10 min)	Ligand challenge at 10 min	Ligand washed out after 10 min incubation and measured cAMP 20–30 min post washing	cAMP following 500 nM α-MSH re-challenge at 55 min
α-MSH, 200 nM	−	++++	−	++++	Full reversal of signal upon washing out
LY2112688, 100 nM	−	++++	−	++++	Full reversal of signal upon washing out
THIQ, 1 µM	−	++++	++	++++	Partial reversal upon washout
MT-II, 200 nM	−	++++	++++	++++	No reversal upon washout
RM-511, 100 nM	−	++++	++++	++++	No reversal upon washout

− represents a zero or basal level response, or response without any ligand exposure; ++ represents about half the maximal cAMP stimulation response; ++++ represents a 100% cAMP stimulation response.