Table 2. Binding Affinities of Guanidino-piperidines 7b, 17a–g and 21 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
7bb	487 ± 117	1052 ± 32	2.2-fold (NPFF1)
17a	441 ± 14	2907 ± 216	6-fold (NPFF1)
17b	3429 ± 377	3220 ± 53
17cb	2692 ± 121	2682 ± 570
17db	2454 ± 338	2223 ± 388
17eb	1623 ± 630	993 ± 87
17fb	1966 ± 324	1620 ± 179
17gb	2348 ± 413	2398 ± 288
21	319 ± 19	405 ± 56

^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-four experiments performed in duplicate.

^bK_i values were determined by using [¹²⁵I]YVP and [¹²⁵I]EYF for hNPFF1-R and hNPFF2-R, respectively, and are the mean ± SEM from two to four experiments performed in duplicate.