“Cells pretreated with melatonin revealed a persistent inhibition (approximately 20%) of forskolin-induced cAMP formation that was not reversed by extensive washes (up to 1 hr) or when luzindole (1 microM) was added together with melatonin during pretreatment.”
“Low concentrations of melatonin (0.01 fM-1 PM) inhibited forskolin (100 microM)-stimulated cAMP formation with an IC50 of 0.1 +/- 0.05 PM (four experiments) and a maximal inhibitory effect (26%) at 1 PM.”
“ Melatonin (0.1 fM-1 nM) inhibited forskolin-induced cAMP formation in a concentration-dependent and biphasic manner.”
“… melatonin (1 … forskolin-induced cAMP formation with an IC50 of 64 +/- 1.8 PM (four experiments) and a maximal inhibition (74%) at 1 nM. Luzindole (1 microM), … antagonist, antagonized the effect of melatonin at the higher concentrations only (IC50 = 1.5 +/- 0.22 nM, pKB = -7.3; three experiments).”