1: Bioorg Med Chem  2003 Mar 20;11(6):817-25 

N-Morpholino- and N-diethyl-analogues of palmitoylethanolamide increase the
sensitivity of transfected human vanilloid receptors to activation by anandamide
without affecting fatty acid amidohydrolase activity.

Vandevoorde S, Lambert DM, Smart D, Jonsson KO, Fowler CJ.

Unite de Chimie pharmaceutique et de Radiopharmacie, Universite catholique de
Louvain, Avenue Mounier, 73, UCL-CMFA 73.40, B-1200 Brussels, Belgium.

The abilities of 19 analogues of palmitoylethanolamide and two analogues of
oleoylethanolamide to affect the Ca(2+) influx into human embryonic kidney cells
expressing the human vanilloid receptor (hVR1-HEK293 cells) in response to
anandamide (AEA) have been investigated using a FLIPR assay and a bovine serum
albumin-containing assay medium. Only palmitoylethanolamide produced any effect
in the absence of AEA. The ability of palmitoylethanolamide to potentiate the
response to AEA was retained when the N-CH(2)CH(2)OH group was replaced by
N-CH(2)CH(2)Cl,whereas replacement with N-alkyl substituents [from -H up to
-(CH(2))(12)CH(3)] resulted either in a reduction or in a complete loss of this
activity. The tertiary amide N-(CH(2)CH(3))(2) (19) and N-morpholino (20)
analogues of palmitoylethanolamide potentiated the response to 1 microM AEA to a
greater degree than the parent compound, whereas the N-(CH(3))(2) analogue was
inactive. 19 and 20 produced leftward shifts in the dose-response curve for AEA
activation of Ca(2+) influx into hVR1-HEK293 cells. EC(50) values for AEA to
produce Ca(2+) influx into hVR1-HEK293 cells were 1.1, 1.1, 0.54 and 0.36 microM
in the presence of 0, 1, 3 and 10 microM 19, respectively. The corresponding
values for 20 were 1.5, 1.3, 0.77 and 0.17 microM, respectively. The compounds
did not affect the dose-response curves to capsaicin. The ability of
oleoylethanolamide to potentiate AEA is retained by the N-CH(2)CH(3) and
N-CH(CH(3))(2) analogues (22 and 23, respectively). 22 and 23 produced a small (
approximately 25%) inhibition of the binding of [(3)H]-CP55,940 and [(3)H]-WIN
55,212-2 to CB(1) and CB(2) receptors, respectively, expressed in CHO cells. The
compounds inhibited the metabolism of 2 microM [(3)H]-AEA by rat brain fatty
acid amidohydrolase with IC(50) values of 5.6 and 11 microM, respectively. In
contrast, 19 and 20 were without effect on either binding to CB receptors or
fatty acid amidohydrolase activity. Minor reductions in the accumulation of 10
microM [(3)H]-AEA into C6 glioma cells were seen at 10 microM concentrations of
19 and 20. It is concluded that 19 and 20 selectively enhance AEA effects upon
VR1 receptors without potentially confounding effects upon CB receptors or fatty
acid amidohydrolase activity.

PMID: 12614867 [PubMed - in process]