Table 3. Binding Affinities of Guanidino-piperidines 26, 30a–d, 34, 42−43, 46, and 49a–g at NPFF1-R and NPFF2-R^a.

cmpd	hNPFF1-R (Ki, nM)	hNPFF2-R (Ki, nM)	ratio
NPVF	3.66 ± 0.95
1DMe	3.85 ± 0.42	0.47 ± 0.08
21	319 ± 19	405 ± 56
26	904 ± 237	1893 ± 490
30a	94 ± 24	309 ± 55	3.3-fold (NPFF1)
30b	114 ± 17	987 ± 65	8.7-fold (NPFF1)
30c	201 ± 35	884 ± 177	4.4-fold (NPFF1)
30d	191 ± 31	409 ± 39	2.1-fold (NPFF1)
34	511 ± 79	3505 ± 847	6.9-fold (NPFF1)
42	417 ± 74	84 ± 12	5-fold (NPFF2)
43	151 ± 15	465 ± 108	3-fold (NPFF1)
46	81 ± 17	1426 ± 49	17.6-fold (NPFF1)
49a	15085 ± 355	2757 ± 81
49b	1638 ± 499	298 ± 14	5.5-fold (NPFF2)
49c	1057 ± 150	330 ± 28	3.2-fold (NPFF2)
49d	538 ± 40	129 ± 26	4.2-fold (NPFF2)
49e	141 ± 34	504 ± 95	3.6-fold (NPFF1)
49f	112 ± 11	454 ± 4	4-fold (NPFF1)
49g	340 ± 91	1513 ± 33	4.5-fold (NPFF1)

^aK_i values were determined by using [³H]NPVF and [³H]EYF for hNPFF1-R and hNPFF2-R, respectively, and are the mean ± SEM from two to four experiments performed in duplicate.